Raz wrote:
Hello
I need to configure 3xDAS'es, each with 12 disks.
All three DAS'es are connected to a single machine.
I have the following requirements (in this order of importance)
from the storage:
1. redundancy.
having two disks failing in one raid5 breaks the entire raid. when
you have 30TB storage
it is a disaster.
2. performance.
My code eliminates Linux raid5/6 write penalty. I managed to do by
manipulating xfs and patching linux raid5 a bit.
3. modularity ( a "grow" and it will be nice to have "shrink" )
file system and volume must be able to grow. shrinking is possible
by unifying multiple file systems
under unionfs or aufs.
4. Utilize storage size.
I assume each disk is 1TB.
___ snip ___
Any other ideas ?
Yes, you have the whole solution rotated 90 degrees. Consider your
original solution #2 below... You have no redundancy if one whole DAS
box fails, which is certainly a possible failure mode. If you put the
RAID0 horizontally, two arrays size six in each DAS, then RAID6
vertically, if one DAS fails completely you still have a functioning
system, and the failure results for individual drives remains about the
same, while the rebuild time will be longer.
Solution #2
raid0
DAS1: raid6: D,D,D,D,D,D |
raid6: D,D,D,D,D,D |
|
DAS2: raid6: D,D,D,D,D,D | xfs.
raid6: D,D,D,D,D,D |
|
DAS3: raid6: D,D,D,D,D,D |
raid6: D,D,D,D,D,D |
In addition, you can expand this configuration by adding more DAS units.
This addresses several of your goals.
In practice, just to get faster rebuild as the array gets larger, I
suspect you would find it was worth making the horizontal arrays RAID5
instead of RAID0, just to minimize time to full performance.
--
bill davidsen <davidsen@xxxxxxx>
CTO TMR Associates, Inc
"You are disgraced professional losers. And by the way, give us our money back."
- Representative Earl Pomeroy, Democrat of North Dakota
on the A.I.G. executives who were paid bonuses after a federal bailout.
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