Re: [gentoo-server] RAID 1+0 question

[Jeroen Geilman]

Patrick Lauer wrote:
> On Wed, 2006-03-01 at 13:40 +0100, Marton Gabor wrote:
>
>> Hi!
>>
>> I'm going to recieve 4x250Gb SATA disks to our new server, and my first
>> idea was to make 2xRAID1 and then make 1xRAID0 out of the RAID1 arrays
>> using Linux software raid so that I have our data mirrored and still I
>> can use 500Gb storage space and handle it as one big "disk".
>> So my questions would be:
>>     - could someone give me a good howto? Sorry, but I have never had
>> the chance to make a RAID array before and I have no experience and
>> Google doesn't seem to be helpful in this case.
>>     - do I need to make a /boot partition which is not part of any
>> arrays or will grub boot from raid1+0?
>>
> grub can boot from raid1, raid0+1 will need a (small) boot partition.
>
> With 4 disks you could also build a raid5 with little overhead, takes a
> tad more cpu and gives you 750G capacity (or 500 with one hotspare)
>
Take note that both using RAID5 and RAID10 in software will use a 
significant amount of CPU*; normally speaking (in a hardware 
configuration) RAID10 would outperform RAID5 by 30% or more, but since 
it's in software the RAID0 has to be layered on top of the RAID1, 
increasing its overhead by no small amount.

I'd go with the RAID1 with LVM solution mentioned earlier if you intend 
to retain any performance worth mentioning.

If there are decent Linux drivers for it, I'd highly recommend a RAID 
card that can do RAID5 or RAID10 in hardware.

*Actually, the RAID10 solution won't use nearly as much CPU as the 
RAID5, but the RAID10 will spend a lot more time waiting on disk I/O, so 
the net result will likely be similar, if not actually worse.



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