[Lustre-discuss] MDS - RAID0 or RAID1

[Brian J. Murrell]

On Tue, 2009-06-23 at 15:14 -0500, Carlos Santana wrote:
> Hi,

Hi,

> What RAID level should be used for MDS configuration? The manual seems
> to suggest RAID1, however, the FAQ suggests RAID0 level.

These are not mutually exclusive.  You can use RAID1 if you want
redundancy and RAID0 if you want to enhance performance with some
striping (although on an MDT, I'm not sure you'd get much bang for your
buck) or need to build a bigger volume than you get with a single disk.
If you use both RAID0 and RAID1, this is usually called or implemented
as RAID10.

Most people use RAID1 for their MDT.  We recommend against RAID5 and
RAID6 for MDTs for performance reasons.

> Also, is it possible to add more OSTs as the requirement grows?

Yes.

> If
> yes, can additional resources be made part of RAID or can we turn
> existing non-RAID system into a RAID system?

I think this is orthogonal to the question of adding OSTs.  How you
build a block device for an OST is up to you.  Once you have a block
device (however you build it), it can be an OST and be added to an
existing filesystem.

b.

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