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Re: RAID for large disks

Thanks for the responses all.

I want RAID 5 but without mirroring. The data is important but not that important.
I am planning to use LVM.

If the controller creates a stripe size of 16k, do I need to do anything special with physical extends (in pvcreate or vgcreate) ?
Do I need to do anything specific when creating a LV? I plan on striping my LV to create extra spindles. Do I need to create my ext3 filesystem with any particular settings? I am looking for a optimal tuning guide with emphasis on performace versus redudancy.

On Sat, Jun 7, 2008 at 4:27 PM, Andrew M.A. Cater <amacater@galactic.demon.co.uk> wrote:
On Sat, Jun 07, 2008 at 12:52:24PM -0400, Mag Gam wrote:
> With the RAID array I am planning to use RAID 5 so my data is still
> protected. My confusion is going with RAID striping (picking the right
> size). Also, Does the filesystem layout need to be specific when I do
> striping? If I am using 128k stripes, should I start my filesystem on 129k
> and end with max-(128+1k)?

You have four or five considerations.

You mentioned you were going to use your 12 disks as two RAID arrays.

If one is going to be for your data and one for a backup of that data -
2 x RAID 5 and then RAID1 [5 x 500 = ~2.5TB mirrored].

If you need maximum data storage - all your disks in one array in RAID

11 x 500, one spare - 5.5TB but you rely on the spare :)

If you need data resilience - all your disks in one array in RAID 6 or

Hardware RAID control is lovely - but you may need battery backup on
some cards to avoid problems on delayed writes. Hardware RAID control
also ties you to one manufacturer's cards and/or recovery utilities if a
RAID fails and you have to recover data.

If you go the hardware route: take the card defaults.

Linux mdadm works well and, under some circumstances, can approach the
performance of a dedicated hardware RAID card - disks can be swapped
into any Linux box to recover the RAID.

You can then add LVM on top.



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