[Ilugc] Nested RAID 0+1 (SW)
- From: rajasuperman@xxxxxxxxx (Raja Subramanian)
- Date: Sun Mar 22 21:04:57 2009
On Sun, Mar 22, 2009 at 1:08 AM, Arun Khan <knura@xxxxxxxxx> wrote:
Has anyone done a 0+1 SW RAID?
I had similar setups a few years ago when Linux did not have
native raid10 support. So I had to create two raid1 devices
and then stripe them with a raid0 device on top.
My setup worked well enough for me to put into production use,
and I think they are still running.
Instead of layering multiple raid levels, new Linux kernels offer
native raid10 support. I have not used this, it would be good
to research this further before making a decision.
I am thinking of configuring 2 disks (sda+sdc) in a RAID0 setup and then
mirror this RAID device on the other 2 disks (sdb+sdd).
Do not do it this way. If a single disk fails, the rebuild will take
too long. Better way to setup is like this:
md0 = raid1 sda+sdc
md1 = raid1 sdb+sdd
md2 = raid0 md0+md1
mkfs on md2
In case of sda failure, only sda+sdc need to be re-synced.
Doing it your way will mean that md0 and md1 need to be
re-synced and will take double the time.
Note that as long as you are not doing RAID parity computation,
as in RAID5/6, SW raid has absolutely no CPU hit. SW RAID0/1
are all good in my book.
- Raja
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