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From: Arno on 10 Mar 2010 12:48
yawnmoth <terra1024(a)yahoo.com> wrote:
> On Mar 10, 7:04?am, Arno <m...(a)privacy.net> wrote:
>> yawnmoth <terra1...(a)yahoo.com> wrote:
>> > On Mar 9, 11:44?am, Arno <m...(a)privacy.net> wrote:
>> >> yawnmoth <terra1...(a)yahoo.com> wrote:
>> >> > I have a hard drive whose contents I'd like to back up. ?I was
>> >> > thinking about using RAID-1 mirroring to do this. ?The thing I'm
>> >> > considered about is... ?will my drive be wiped? ?
>> >> Yes.
>> >> > My second drive I
>> >> > don't really care about - that drives purpose is to just serve as a
>> >> > backup. ?But my main drive... ?I do care about that and reformating
>> >> > would rather defeat the point.
>> >> The way to do this with a decent RAID conttroller or software
>> >> RAID is as follows: Set up a degraded RAID1 with the second
>> >> driv. Partition it and create the filesystem. Then copy everything
>> >> over from the first fdirve. And then add the frist drive to
>> >> the degraded RAID1 array to get redundancy.
>> > Any idea as to what RAID controllers might provide that
>> > functionality? ?
>> I don't know. Linux Software RAID does it and any good controller
>> should do it, but then the question is what constitutes a good
>> > <http://www.rosewill.com/products/942/
>> > productDetail.htm> looked like a good RAID controller
>> That is Fake Raid, i.e. not a RAID controller at all. I have
>> one with the same chip, this is a plain 2 port SATA controller.
>> What happens here is that this thing has software RAID in the
>> BIOS, which turns out to be the wortst possible way to do RAID.
>> Example of a real hardware controller:http://www.3ware.com/products/serial_ata2-9650.asp
>> A bit more expensive though.
> Also, is there a way to easily tell if an arbitrary card uses BIOS
> software RAID or has "real" RAID controllers? And what advantage does
> real RAID have over software RAID, be it Linux or BIOS? I assume less
> CPU usage overhead?
It used to be a speed question. It is not anymore.
Basically, hardware RAID has the following advantages:
- automated hotplug and rebuild, enclosure support
- low/no OS dependency
for Linux Software RAID you get
- can work on partitions
- very easy to monitor and administrate
Speed-wise they are pretty much the same if the software RAID
goes over a PCI-E attached controller.
As to recognition, if it is > 300EUR/USD, it is hardware RAID ;-)
Arno Wagner, Dr. sc. techn., Dipl. Inform., CISSP -- Email: arno(a)wagner.name
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