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From: David Brown on 14 May 2010 16:20
Rod Speed wrote:
> David Brown wrote
>> me wrote
>>> David Brown <david(a)westcontrol.removethisbit.com> wrote
>
>>>> Remember, raid is not about keeping your data safe - that's
>>>> what backups are for. raid is about speed, and uptime -
>>>> redundant raid means you won't have to restore data from
>>>> backups or re-install your OS just because a hard disk died.
>
>>> Thanks for all the info. What makes the Intel mobo implementation
>>> "fakeraid" instead of hardware raid?
>
>> "Fakeraid" is a generic term for motherboard-based raid that has
>> become common in the last few years, which is not really anything
>> more than a limited form of software raid supported by the bios.
>
>> In proper software raid, the OS low-level layers accesses the disks
>> as individual SATA (or IDE, SCSI, whatever) disks. The OS raid
>> layer handles the combining of these, and the file systems and
>> user-level software see the raid setup as a single disk. This
>> gives a lot of flexibility - the OS can support many types of raid
>> setups, it can combine partitions into raid sets rather than whole
>> disks, it can take advantage of greater knowledge of the file
>> access patterns to improve performance, and it can provide features
>> that you don't get with hardware raid systems (or at least, not
>> without paying a great deal of money). For example, I believe
>> Linux mdadm raid is the only system that will let you have raid 1+0
>> on any number of disks (greater than 1, obviously) - it will
>> happily let you have striped and mirrored raid on 2 or 3 disks,
>> while hardware solutions will require a multiple of 4 disks. And if
>> the OS or the hardware dies, you can put the same disk set in
>> another computer with the same OS, and access your drives.
>
>> The disadvantage of software raid is that if the OS dies, or the
>> power to the motherboard fails, you could be in big trouble and get
>> your disks out of sync. You are also using the main processor to
>> do the work, but that's seldom an issue these days unless your
>> processor is already heavily loaded. Raid 0 and 1 levels are
>> particularly light on processor use.
>
>> With proper hardware raid, the controller card is separate so the
>> OS only ever sees a single large disks. All processing such as
>> parity generation, syncing, checking, etc., is handled by the card
>> without taking host processor cycles. And the controller card will
>> typically have a battery backup (or non-volatile memory) to provide
>> consistency and reliability even if you get a power fail. It won't
>> protect you from logical faults if the OS dies, but it will protect
>> you from raid set inconsistencies. For very large setups and
>> expensive hardware, hardware raid can perform better than software
>> raid even with just raid 0 or 1.
>
> But as you say, thats not usually a problem with modern systems.
>
>> If the hardware controller dies, you will typically need to get the
>> same model or a similar model to replace it, since manufacturers
>> use different arrangements for their raid setups.
>
> And you really need to keep a spare of what is the most expensive
> approach too.
>

That depends on why you are using raid - if it is for improved uptime,
you might well want a spare card on-hand. If it is for improved speed,
it is probably not necessary.

Generally speaking, I would say that if you are concerned enough about
uptime to want a spare hardware raid controller, you are better off
setting up a redundant system or a hot spare of the entire system.
After all, the raid card is not a weak point in the system - things like
power supplies are much more likely to fail, as is the motherboard. But
you will at least want to make sure replacement parts are easily available.

>> Fakeraid gives you the worst of both worlds.
>
> Thats overstating it, particularly with price.
>

The price is good, certainly - but not any better than the price of
software raid.

>> There is no separate processor, so everything is handled by the
>> host - either by BIOS routines, or drivers loaded by the OS.
>
> But as you say, thats not a problem with modern systems and the
> simpler forms of RAID.
>

It's not a problem - certainly not in terms of performance. But it
means you have the same vulnerabilities to power failures or system
crashes as you do with software raid.

>> You don't get the full flexibility of proper software raid, but
>> only the limited functionality provided by the fakeraid. And
>> access to the disk is limited to the chipset used in the
>> motherboard - if the motherboard dies (more likely than a hardware
>> raid controller dying),
>
> That last is very arguable.
>

Motherboards are a higher risk component than a raid card. They are
high power, high speed, and dense boards, leaving them very vulnerable
to overheating if you have problems with your fans or cooling systems.
They are connected to all sorts of external devices, making them
vulnerable to external wrong connections or misuse (depending on the
usage environment, of course). And the heavy competition in the market
leads to low-cost shortcuts sometimes being taken in the design and
manufacture of motherboards. Raid controller cards are simpler,
dedicated to a specific job, and aimed for a market which places value
on reliability and stability.

Of course, you can still argue about it - and you can probably find
motherboards with a better track record than some hardware raid cards,
so it's worth doing some research before buying.

>> you could lose access to your disks.
>
> Not necessarily forever and a spare motherboard is going to cost less
> than the spare controller with fancy hardware raid too.
>

It's certainly true that a good hardware raid card will cost more than a
typical motherboard, so if you are buying spares, the motherboard is
cheaper. But if you are looking at this over a long term, motherboard
designs (and in particular, chipsets and bios versions) come and go a
lot faster than raid card designs. And even if your particular model of
raid card is no longer available, newer models from the same company
will often be compatible with the older drives - motherboard fakeraid
gives no such promises.

Of course, software raid is a better choice if this is an important
issue, since the same OS will work on a wide range of hardware.

>> Where fakeraid wins is if you are using a limited OS like windows,
>> and want to install the whole system on a raid drive but don't want
>> to pay for a hardware raid card.
>
> So it isnt actually the worst of both worlds.
>
>> As far as I know, you can't install windows on a windows software
>> raid drive
>
> Yes you can.
>
>> - you can only use such drives for non-system partitions.
>
> Thats just plain wrong.
>

OK - I was careful to prefix that statement with "as far as I know".
It's not something I've tried, and the quick google I did about windows
software raid turned up plenty of information about making dynamic disk
raid sets on extra drives and partitions, but the only article I found
about windows software raid and windows system partitions said that it
couldn't be done. But you know more about such setups than I do, so
I'll take your word for it that it's possible.


From: Rod Speed on 14 May 2010 19:02
David Brown wrote
> Rod Speed wrote
>> David Brown wrote
>>> me wrote
>>>> David Brown <david(a)westcontrol.removethisbit.com> wrote

>>>>> Remember, raid is not about keeping your data safe - that's
>>>>> what backups are for. raid is about speed, and uptime -
>>>>> redundant raid means you won't have to restore data from
>>>>> backups or re-install your OS just because a hard disk died.

>>>> Thanks for all the info. What makes the Intel mobo implementation "fakeraid" instead of hardware raid?

>>> "Fakeraid" is a generic term for motherboard-based raid that has
>>> become common in the last few years, which is not really anything
>>> more than a limited form of software raid supported by the bios.

>>> In proper software raid, the OS low-level layers accesses the disks
>>> as individual SATA (or IDE, SCSI, whatever) disks. The OS raid
>>> layer handles the combining of these, and the file systems and
>>> user-level software see the raid setup as a single disk. This
>>> gives a lot of flexibility - the OS can support many types of raid
>>> setups, it can combine partitions into raid sets rather than whole
>>> disks, it can take advantage of greater knowledge of the file
>>> access patterns to improve performance, and it can provide features
>>> that you don't get with hardware raid systems (or at least, not
>>> without paying a great deal of money). For example, I believe
>>> Linux mdadm raid is the only system that will let you have raid 1+0
>>> on any number of disks (greater than 1, obviously) - it will
>>> happily let you have striped and mirrored raid on 2 or 3 disks,
>>> while hardware solutions will require a multiple of 4 disks. And if
>>> the OS or the hardware dies, you can put the same disk set in
>>> another computer with the same OS, and access your drives.

>>> The disadvantage of software raid is that if the OS dies, or the
>>> power to the motherboard fails, you could be in big trouble and get
>>> your disks out of sync. You are also using the main processor to
>>> do the work, but that's seldom an issue these days unless your
>>> processor is already heavily loaded. Raid 0 and 1 levels are
>>> particularly light on processor use.

>>> With proper hardware raid, the controller card is separate so the
>>> OS only ever sees a single large disks. All processing such as
>>> parity generation, syncing, checking, etc., is handled by the card
>>> without taking host processor cycles. And the controller card will
>>> typically have a battery backup (or non-volatile memory) to provide
>>> consistency and reliability even if you get a power fail. It won't
>>> protect you from logical faults if the OS dies, but it will protect
>>> you from raid set inconsistencies. For very large setups and
>>> expensive hardware, hardware raid can perform better than software
>>> raid even with just raid 0 or 1.

>> But as you say, thats not usually a problem with modern systems.

>>> If the hardware controller dies, you will typically need to get the
>>> same model or a similar model to replace it, since manufacturers
>>> use different arrangements for their raid setups.

>> And you really need to keep a spare of what is the most expensive approach too.

> That depends on why you are using raid - if it is for improved uptime, you might well want a spare card on-hand. If
> it is for improved speed,

Thats unlikely with real hardware raid. It makes more sense to buy faster drives instead.

> it is probably not necessary.

> Generally speaking, I would say that if you are concerned enough about uptime to want a spare hardware raid
> controller, you are better off setting up a redundant system or a hot spare of the entire system.

Yes, but if you want improved speed, you are better off with faster drives etc.

> After all, the raid card is not a weak point in the system - things like power supplies are much more likely to fail,
> as is the motherboard.

I dont believe that last.

> But you will at least want to make sure replacement parts are easily available.

And the only real way to do that is to buy two.

>>> Fakeraid gives you the worst of both worlds.

>> Thats overstating it, particularly with price.

> The price is good, certainly - but not any better than the price of software raid.

Depends. The versions of Win that can do that arent cheap.

Its essentially free with motherboard raid.

>>> There is no separate processor, so everything is handled by the host - either by BIOS routines, or drivers loaded by
>>> the OS.

>> But as you say, thats not a problem with modern systems and the> simpler forms of RAID.

> It's not a problem - certainly not in terms of performance. But it means you have the same vulnerabilities to power
> failures

Not really if you are fully backed up.

> or system crashes as you do with software raid.

Thats very arguable too.

>>> You don't get the full flexibility of proper software raid, but only the limited functionality provided by the
>>> fakeraid. And access to the disk is limited to the chipset used in the motherboard - if the motherboard dies (more
>>> likely than a hardware raid controller dying),

>> That last is very arguable.

> Motherboards are a higher risk component than a raid card.

Easy to claim. Have fun actually substantiating that claim.

> They are high power,

Nope. And that doesnt affect reliability anyway.

> high speed, and dense boards, leaving them very vulnerable to overheating if you have problems with your fans or
> cooling systems.

Not if you have a clue and use decent alarm systems for fan failure etc.

> They are connected to all sorts of external devices, making them vulnerable to external wrong connections or misuse

In practice thats not normally a problem in the sense of the raid.

> (depending on the usage environment, of course). And the heavy competition in the market leads to low-cost shortcuts
> sometimes being taken in the design and manufacture of motherboards.

Or you can buy decent quality motherboards.

> Raid controller cards are simpler,

In some way they are, in some ways they arent.

> dedicated to a specific job,

Irrelevant to the reliability.

> and aimed for a market which places value on reliability and stability.

And you pay a lot for that.

> Of course, you can still argue about it - and you can probably find motherboards with a better track record than some
> hardware raid cards, so it's worth doing some research before buying.

Its not that easy to research, particularly with hardware raid reliability.

>>> you could lose access to your disks.

>> Not necessarily forever and a spare motherboard is going to cost less than the spare controller with fancy hardware
>> raid too.

> It's certainly true that a good hardware raid card will cost more than a typical motherboard,

And you need some motherboard anyway with
good hardware raid, so thats more than double.

> so if you are buying spares, the motherboard is cheaper. But if you are looking at this over a long term, motherboard
> designs (and in particular, chipsets and bios versions) come and go a lot faster than raid card designs.

Doesnt mean you have to bother with many of the changes.

> And even if your particular model of raid card is no longer available, newer models from the same company will often
> be compatible with the older drives

Not if the manufacturer has disappeared.

> - motherboard fakeraid gives no such promises.

But anyone with a clue has full backups anyway.

> Of course, software raid is a better choice if this is an important
> issue, since the same OS will work on a wide range of hardware.

Yes, but OSs that support software raid well arent necessarily that cheap.

>>> Where fakeraid wins is if you are using a limited OS like windows,
>>> and want to install the whole system on a raid drive but don't want
>>> to pay for a hardware raid card.

>> So it isnt actually the worst of both worlds.

>>> As far as I know, you can't install windows on a windows software raid drive

>> Yes you can.

>>> - you can only use such drives for non-system partitions.

>> Thats just plain wrong.

> OK - I was careful to prefix that statement with "as far as I know".
> It's not something I've tried, and the quick google I did about
> windows software raid turned up plenty of information about making
> dynamic disk raid sets on extra drives and partitions, but the only
> article I found about windows software raid and windows system
> partitions said that it couldn't be done.

It can anyway.

> But you know more about such setups than I do, so I'll take your word for it that it's possible.


From: David Brown on 15 May 2010 13:16
Rod Speed wrote:
> David Brown wrote
>> Rod Speed wrote
>>> David Brown wrote
>>>> me wrote
>>>>> David Brown <david(a)westcontrol.removethisbit.com> wrote
>
>>>>>> Remember, raid is not about keeping your data safe - that's
>>>>>> what backups are for. raid is about speed, and uptime -
>>>>>> redundant raid means you won't have to restore data from
>>>>>> backups or re-install your OS just because a hard disk
>>>>>> died.
>
>>>>> Thanks for all the info. What makes the Intel mobo
>>>>> implementation "fakeraid" instead of hardware raid?
>
>>>> "Fakeraid" is a generic term for motherboard-based raid that
>>>> has become common in the last few years, which is not really
>>>> anything more than a limited form of software raid supported by
>>>> the bios.
>
>>>> In proper software raid, the OS low-level layers accesses the
>>>> disks as individual SATA (or IDE, SCSI, whatever) disks. The OS
>>>> raid layer handles the combining of these, and the file systems
>>>> and user-level software see the raid setup as a single disk.
>>>> This gives a lot of flexibility - the OS can support many types
>>>> of raid setups, it can combine partitions into raid sets rather
>>>> than whole disks, it can take advantage of greater knowledge of
>>>> the file access patterns to improve performance, and it can
>>>> provide features that you don't get with hardware raid systems
>>>> (or at least, not without paying a great deal of money). For
>>>> example, I believe Linux mdadm raid is the only system that
>>>> will let you have raid 1+0 on any number of disks (greater than
>>>> 1, obviously) - it will happily let you have striped and
>>>> mirrored raid on 2 or 3 disks, while hardware solutions will
>>>> require a multiple of 4 disks. And if the OS or the hardware
>>>> dies, you can put the same disk set in another computer with
>>>> the same OS, and access your drives.
>
>>>> The disadvantage of software raid is that if the OS dies, or
>>>> the power to the motherboard fails, you could be in big trouble
>>>> and get your disks out of sync. You are also using the main
>>>> processor to do the work, but that's seldom an issue these days
>>>> unless your processor is already heavily loaded. Raid 0 and 1
>>>> levels are particularly light on processor use.
>
>>>> With proper hardware raid, the controller card is separate so
>>>> the OS only ever sees a single large disks. All processing
>>>> such as parity generation, syncing, checking, etc., is handled
>>>> by the card without taking host processor cycles. And the
>>>> controller card will typically have a battery backup (or
>>>> non-volatile memory) to provide consistency and reliability
>>>> even if you get a power fail. It won't protect you from
>>>> logical faults if the OS dies, but it will protect you from
>>>> raid set inconsistencies. For very large setups and expensive
>>>> hardware, hardware raid can perform better than software raid
>>>> even with just raid 0 or 1.
>
>>> But as you say, thats not usually a problem with modern systems.
>
>>>> If the hardware controller dies, you will typically need to get
>>>> the same model or a similar model to replace it, since
>>>> manufacturers use different arrangements for their raid setups.
>>>>
>
>>> And you really need to keep a spare of what is the most expensive
>>> approach too.
>
>> That depends on why you are using raid - if it is for improved
>> uptime, you might well want a spare card on-hand. If it is for
>> improved speed,
>
> Thats unlikely with real hardware raid. It makes more sense to buy
> faster drives instead.
>
>> it is probably not necessary.
>
>> Generally speaking, I would say that if you are concerned enough
>> about uptime to want a spare hardware raid controller, you are
>> better off setting up a redundant system or a hot spare of the
>> entire system.
>
> Yes, but if you want improved speed, you are better off with faster
> drives etc.
>

Drive speed is limited - people use raid as a way to increase speed. I
agree that it doesn't normally make sense to use hardware raid cards for
speed purposes - the money is better spent on the drives and using
software raid. Hardware raid cards make sense from a reliability
viewpoint, not speed. But that does not mean that people /don't/ use
hardware raid cards when they want a faster disk system.

>> After all, the raid card is not a weak point in the system - things
>> like power supplies are much more likely to fail, as is the
>> motherboard.
>
> I dont believe that last.
>

Do you think that hardware raid cards are more likely to fail than
motherboards? Well, I guess you are free to believe that if you want,
and I'm not likely to be able to change your mind. I have seen enough
motherboard failures to know that they do sometimes fail - I have not
seen enough hardware raid cards to be sure that they /don't/ fail.

>> But you will at least want to make sure replacement parts are
>> easily available.
>
> And the only real way to do that is to buy two.
>

That depends on the level of security you are looking for. Buying a
spare is, of course, the best security - but you might have a supplier
that you trust enough to believe their assurances that they have
replacements in stock.

>>>> Fakeraid gives you the worst of both worlds.
>
>>> Thats overstating it, particularly with price.
>
>> The price is good, certainly - but not any better than the price of
>> software raid.
>
> Depends. The versions of Win that can do that arent cheap.
>

I might be wrong here, but I thought even the "home" versions of Win7
supported some sort of raid (raid 0, and perhaps raid 1)?

But if you have to buy a more expensive version of windows just to get
the software raid, then obviously it is no longer free.

And of course any version of Linux will support software raid (though
some distros make it easier to use than others).

> Its essentially free with motherboard raid.
>
>>>> There is no separate processor, so everything is handled by the
>>>> host - either by BIOS routines, or drivers loaded by the OS.
>
>>> But as you say, thats not a problem with modern systems and the>
>>> simpler forms of RAID.
>
>> It's not a problem - certainly not in terms of performance. But it
>> means you have the same vulnerabilities to power failures
>
> Not really if you are fully backed up.
>

Backup protects your data, but not your uptime. The problem with raid
and power failures is that you can get your stripes out of sync -
perhaps you have written data to one part of a mirror, but not the
second copy. A good hardware raid card will protect you from that
situation using a battery or non-volatile caches - software raid or
fakeraid will not. The file system's logs and journals may be
sufficient to recover from such a situation.

And of course, as you took pains to point out to me in a previous
thread, backups only save your data from your last backup - raid can
help preserve data saved since the last backup.

>> or system crashes as you do with software raid.
>
> Thats very arguable too.
>

A system crash can have the same effect on the data storage as having
the power pulled out unexpectedly.

<snip for brevity>

>
>> Of course, software raid is a better choice if this is an important
>> issue, since the same OS will work on a wide range of hardware.
>
> Yes, but OSs that support software raid well arent necessarily that
> cheap.
>

Linux has better support for software raid than anything else I know of.
You can get it free, or pay for supported versions, according to your
requirements.

If you are thinking about things like the windows server versions, or
AIX, Solaris, or other bigger OS's, it's likely that you'll choose these
for other reasons - the software raid support is probably a small issue,
and is thus effectively a free bonus.

>>>> Where fakeraid wins is if you are using a limited OS like
>>>> windows, and want to install the whole system on a raid drive
>>>> but don't want to pay for a hardware raid card.
>
>>> So it isnt actually the worst of both worlds.
>
>>>> As far as I know, you can't install windows on a windows
>>>> software raid drive
>
>>> Yes you can.
>
>>>> - you can only use such drives for non-system partitions.
>
>>> Thats just plain wrong.
>
>> OK - I was careful to prefix that statement with "as far as I
>> know". It's not something I've tried, and the quick google I did
>> about windows software raid turned up plenty of information about
>> making dynamic disk raid sets on extra drives and partitions, but
>> the only article I found about windows software raid and windows
>> system partitions said that it couldn't be done.
>
> It can anyway.
>
>> But you know more about such setups than I do, so I'll take your
>> word for it that it's possible.
>
>
From: Rod Speed on 15 May 2010 14:45
David Brown wrote:
> Rod Speed wrote:
>> David Brown wrote
>>> Rod Speed wrote
>>>> David Brown wrote
>>>>> me wrote
>>>>>> David Brown <david(a)westcontrol.removethisbit.com> wrote

>>>>>>> Remember, raid is not about keeping your data safe - that's
>>>>>>> what backups are for. raid is about speed, and uptime -
>>>>>>> redundant raid means you won't have to restore data from
>>>>>>> backups or re-install your OS just because a hard disk died.

>>>>>> Thanks for all the info. What makes the Intel mobo
>>>>>> implementation "fakeraid" instead of hardware raid?

>>>>> "Fakeraid" is a generic term for motherboard-based raid that
>>>>> has become common in the last few years, which is not really
>>>>> anything more than a limited form of software raid supported by
>>>>> the bios.

>>>>> In proper software raid, the OS low-level layers accesses the
>>>>> disks as individual SATA (or IDE, SCSI, whatever) disks. The OS
>>>>> raid layer handles the combining of these, and the file systems
>>>>> and user-level software see the raid setup as a single disk.
>>>>> This gives a lot of flexibility - the OS can support many types
>>>>> of raid setups, it can combine partitions into raid sets rather
>>>>> than whole disks, it can take advantage of greater knowledge of
>>>>> the file access patterns to improve performance, and it can
>>>>> provide features that you don't get with hardware raid systems
>>>>> (or at least, not without paying a great deal of money). For
>>>>> example, I believe Linux mdadm raid is the only system that
>>>>> will let you have raid 1+0 on any number of disks (greater than
>>>>> 1, obviously) - it will happily let you have striped and
>>>>> mirrored raid on 2 or 3 disks, while hardware solutions will
>>>>> require a multiple of 4 disks. And if the OS or the hardware
>>>>> dies, you can put the same disk set in another computer with
>>>>> the same OS, and access your drives.

>>>>> The disadvantage of software raid is that if the OS dies, or
>>>>> the power to the motherboard fails, you could be in big trouble
>>>>> and get your disks out of sync. You are also using the main
>>>>> processor to do the work, but that's seldom an issue these days
>>>>> unless your processor is already heavily loaded. Raid 0 and 1
>>>>> levels are particularly light on processor use.

>>>>> With proper hardware raid, the controller card is separate so
>>>>> the OS only ever sees a single large disks. All processing
>>>>> such as parity generation, syncing, checking, etc., is handled
>>>>> by the card without taking host processor cycles. And the
>>>>> controller card will typically have a battery backup (or
>>>>> non-volatile memory) to provide consistency and reliability
>>>>> even if you get a power fail. It won't protect you from
>>>>> logical faults if the OS dies, but it will protect you from
>>>>> raid set inconsistencies. For very large setups and expensive
>>>>> hardware, hardware raid can perform better than software raid
>>>>> even with just raid 0 or 1.

>>>> But as you say, thats not usually a problem with modern systems.

>>>>> If the hardware controller dies, you will typically need to get
>>>>> the same model or a similar model to replace it, since
>>>>> manufacturers use different arrangements for their raid setups.

>>>> And you really need to keep a spare of what is the most expensive approach too.

>>> That depends on why you are using raid - if it is for improved
>>> uptime, you might well want a spare card on-hand. If it is for
>>> improved speed,

>> Thats unlikely with real hardware raid. It makes more sense to buy
>> faster drives instead.

>>> it is probably not necessary.

>>> Generally speaking, I would say that if you are concerned enough
>>> about uptime to want a spare hardware raid controller, you are better off setting up a redundant system or a hot
>>> spare of the entire system.

>> Yes, but if you want improved speed, you are better off with faster drives etc.

> Drive speed is limited

No it isnt any more than raid speed is limited.

> - people use raid as a way to increase speed.

Not much anymore with personal desktop systems.

> I agree that it doesn't normally make sense to use hardware raid cards for speed purposes

Which is what I said.

> - the money is better spent on the drivesand using software raid.

Not necessarily, particularly with expensive software raid.

> Hardware raid cards make sense from a reliability viewpoint, not speed.

Which is what I said.

> But that does not mean that people /don't/ use hardware raid cards when they want a faster disk system.

Very few do with the personal desktop systems being discussed.

>>> After all, the raid card is not a weak point in the system - things like power supplies are much more likely to
>>> fail, as is the motherboard.

>> I dont believe that last.

> Do you think that hardware raid cards are more likely to fail than motherboards?

Nope, you have a problem with your logic there. ALL I said that motherboards
are not MUCH MORE LIKELY to fail than a hardware raid card.

> Well, I guess you are free to believe that if you want,

Having fun thrashing that straw man ?

> and I'm not likely to be able to change your mind.

Yes, you dont have a shred of evidence that motherboards
are MUCH MORE LIKELY to fail than a hardware raid card.

> I have seen enough motherboard failures to know that they do sometimes fail - I have not seen enough hardware raid
> cards to be sure that they /don't/ fail.

So your opinion on that is completely irrelevant.

>>> But you will at least want to make sure replacement parts are easily available.

>> And the only real way to do that is to buy two.

> That depends on the level of security you are looking for. Buying a spare is, of course, the best security - but you
> might have a supplier that you trust enough to believe their assurances that they have replacements in stock.

Doesnt mean that they will have when you need one.

>>>>> Fakeraid gives you the worst of both worlds.

>>>> Thats overstating it, particularly with price.

>>> The price is good, certainly - but not any better than the price of software raid.

>> Depends. The versions of Win that can do that arent cheap.

> I might be wrong here, but I thought even the "home" versions of Win7
> supported some sort of raid (raid 0, and perhaps raid 1)?

Yes, you are wrong.

> But if you have to buy a more expensive version of windows just to get the software raid, then obviously it is no
> longer free.

What I said.

> And of course any version of Linux will support software raid (though some distros make it easier to use than others).

And plenty dont want to use that OS for various reasons.

>> Its essentially free with motherboard raid.

>>>>> There is no separate processor, so everything is handled by the host - either by BIOS routines, or drivers loaded
>>>>> by the OS.

>>>> But as you say, thats not a problem with modern systems and the>
>>>> simpler forms of RAID.

>>> It's not a problem - certainly not in terms of performance. But it means you have the same vulnerabilities to power
>>> failures

>> Not really if you are fully backed up.

> Backup protects your data, but not your uptime.

Uptime is not normally a problem with the personal desktop systems being discussed
and duplication is a much better way of ensuring uptime when it is important.

> The problem with raid and power failures is that you can get your stripes out of sync

And that can be avoided with a UPS.

> perhaps you have written data to one part of a mirror, but not the second copy. A good hardware raid card will
> protect you from that situation using a battery or non-volatile caches -

And a UPS avoids the problem with motherboard raid or software raid.

> software raid or fakeraid will not.

Yes it will with a UPS.

> The file system's logs and journals may be sufficient to recover from such a situation.

And you dont need that if you use a UPS.

> And of course, as you took pains to point out to me in a previous
> thread, backups only save your data from your last backup - raid can help preserve data saved since the last backup.

And continuous backup is also perfectly possible.

>>> or system crashes as you do with software raid.

>> Thats very arguable too.

> A system crash can have the same effect on the data storage as having the power pulled out unexpectedly.

But hardly ever does.

>>> Of course, software raid is a better choice if this is an important
>>> issue, since the same OS will work on a wide range of hardware.

>> Yes, but OSs that support software raid well arent necessarily that cheap.

> Linux has better support for software raid than anything else I know of.

And plenty prefer not to use it for personal desktop systems for a reason.

> You can get it free, or pay for supported versions, according to your requirements.

And plenty prefer not to use it for personal desktop systems for a reason.

> If you are thinking about things like the windows server versions, or AIX, Solaris, or other bigger OS's, it's likely
> that you'll choose
> these for other reasons - the software raid support is probably a
> small issue, and is thus effectively a free bonus.

I wasnt talking about support.

>>>>> Where fakeraid wins is if you are using a limited OS like
>>>>> windows, and want to install the whole system on a raid drive but don't want to pay for a hardware raid card.

>>>> So it isnt actually the worst of both worlds.

>>>>> As far as I know, you can't install windows on a windows software raid drive

>>>> Yes you can.

>>>>> - you can only use such drives for non-system partitions.

>>>> Thats just plain wrong.

>>> OK - I was careful to prefix that statement with "as far as I
>>> know". It's not something I've tried, and the quick google I did
>>> about windows software raid turned up plenty of information about
>>> making dynamic disk raid sets on extra drives and partitions, but
>>> the only article I found about windows software raid and windows
>>> system partitions said that it couldn't be done.

>> It can anyway.

>>> But you know more about such setups than I do, so I'll take your word for it that it's possible.


From: David Brown on 15 May 2010 16:09
Rod Speed wrote:

<snip>

Well, I hope the OP got the information he was looking for here, because
now that you've started revving up the rodbot autoresponder, I'm
dropping the thread before you get /really/ silly.
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