[Gluster-users] Best practices for creating bricks

[Brian Candler]

On Wed, Oct 31, 2012 at 03:59:15PM -0400, Kushnir, Michael (NIH/NLM/LHC) [C] wrote:
>    I am working with several Dell PE720xd. I have 24 disks per server at
>    my disposal with a high end raid card with 1GB RAM and BBC. I will be
>    building a distributed-replicated volume. Is it better for me to set up
>    one or two large RAID0 arrays and use those as bricks, or should I make
>    each hard drive a brick?

I would recommend neither. Remember that drives *will* fail and you need to
be ready to handle these events.

- a RAID0 array has the problem that if one disk fails, you lose the entire
filesystem.  Therefore you replace the bad drive, make a fresh filesystem,
and then have to resync the *entire* contents from the other gluster node. 
If you get a second disk failure during that time, you have lost everything.

- separate disks per brick is less bad, but is harder to manage.  A disk
failure involves swapping the drive, building a new filesystem on it,
re-adding it into gluster, and letting it resync across.  This needs to be a
well-trodden path operationally, and also you need suitable monitoring in
place to know when a brick has gone down.

Personally I would say: if write performance is relatively unimportant, then
use RAID6 for the arrays.  If write performance is important, then use
RAID10 (and accept a 50% loss of capacity)

What you get from either RAID6 or RAID10 is a no-brainer way to replace
failed disks and have the array reconstruct itself automatically, plus
standard tools for monitoring and managing the array.

This is my personal point of view: others may differ. It also depends on how
important your data is to you (but the implication from building a
replicated volume is that your data *is* important)

Regards,

Brian.