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From: Mark F on 6 Apr 2008 18:06
(Sorry for the late response)
On Tue, 26 Feb 2008 23:34:20 GMT, "Rob Nicholson"
<nicholson.rob(a)spamme.com> wrote:

> We've just installed a rather nice JBOD external enclosure with 4 x 1TB hard
> disks for use as backup-to-disk with Backup Exec. Whilst we've got oodles of
> backup storage for now (~two months back), we may need a lot more soon as
> we're using a lot more space for video recently.
>
> Anyone know what the road map is looking like for >1TB disks?
I think we can assume that it will be possible for the capacity of
disk drives to increase by another factor of 16 or so in 6 years or
less.

However, the home market might be more driven by the need to do
a complete disk image in a fixed about of time and perhaps smaller
devices that use less power.

Looking at the 1tB disks that are around now, .1gB/second seems
to be about the maximum read or write speed. So it takes about
3 hours to read such a disk in order to make an image backup.

With the right kinds of file system a reliable backup can be made
that just looks at incremental changes, but for the typical home
user using NTFS the only way to get a reliable backup of the system
disk is to image the entire drive. Therefore, it would take about
3 hours to make a useful backup, 6 hours if a verify operation
were done. Since most people already don't do backups I think that
many home users already use drives that are too big.


Note that it is possible to stripe disks to speed up the backups
and compares. This allows for a 2 to 4 fold increase in partition
size while keeping the same backup and restore time.

(Yes, many specialized applications work fine with incremental
backups, but for the typical home user the system disk should be
fully backed up. In fact, if you have more than one disk on your
system, the system disk should be kept small so that when the
telephone support people as for diagnostics to be run on the system
disk it take 20 minutes for an 80gB disk, rather than 4 hours
for a 1tB disk.)
From: Rod Speed on 6 Apr 2008 18:21
Mark F <mark49607(a)gmail.com> wrote
> (Sorry for the late response)
> Rob Nicholson <nicholson.rob(a)spamme.com> wrote

>> We've just installed a rather nice JBOD external enclosure with 4 x 1TB
>> hard disks for use as backup-to-disk with Backup Exec. Whilst we've got
>> oodles of backup storage for now (~two months back), we may need a
>> lot more soon as we're using a lot more space for video recently.

>> Anyone know what the road map is looking like for >1TB disks?

> I think we can assume that it will be possible for the capacity of disk
> drives to increase by another factor of 16 or so in 6 years or less.

> However, the home market might be more driven by the
> need to do a complete disk image in a fixed about of time

Nope.

> and perhaps smaller devices that use less power.

Unlikely.

> Looking at the 1tB disks that are around now, .1gB/second seems
> to be about the maximum read or write speed. So it takes about
> 3 hours to read such a disk in order to make an image backup.

> With the right kinds of file system a reliable backup can be
> made that just looks at incremental changes, but for the
> typical home user using NTFS the only way to get a reliable
> backup of the system disk is to image the entire drive.

Oh bullshit.

> Therefore, it would take about 3 hours to make a
> useful backup, 6 hours if a verify operation were done.

Or with drives getting cheaper and cheaper, you will see a lot
more use of RAID etc for backup against hardware failure etc
and the time to do an image backup is completely irrelevant.

> Since most people already don't do backups I think that
> many home users already use drives that are too big.

Irrelevant to what is perfectly possible if you have enough of a clue to do backups.

> Note that it is possible to stripe disks to speed up the backups
> and compares. This allows for a 2 to 4 fold increase in partition
> size while keeping the same backup and restore time.

And it makes a hell of a lot more sense to not do image backups with drives that big.

> (Yes, many specialized applications work fine with incremental backups,
> but for the typical home user the system disk should be fully backed up.

Doesnt have to be backed up using an image backup.

> In fact, if you have more than one disk on your system, the system disk should be kept
> small so that when the telephone support people as for diagnostics to be run on the
> system disk it take 20 minutes for an 80gB disk, rather than 4 hours for a 1tB disk.)

Gets sillier by the minute.


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