[Beowulf] RAID for home beowulf
hahn at mcmaster.ca
Sat Oct 3 18:49:20 EDT 2009
> because parity has to be calculated and written to the disk. In fact this
> performance penalty has lead to a campaign against RAID5:
redundancy costs - your only choice is what kind of redundancy you want.
raid5 has its issues, but really what's needed is redundancy managed
by the filesystem. doing it block-level is what introduces the pain.
>> 3) I'll leave the /boot partition on one of the 3 disks and it will NOT
>> be included in the RAID array, is this ok?
> I think you'd be better off putting your system one one of your three disks,
> and making a RAID1 for /home from the other two. This will give you a
I disagree. for one, I strongly advice against partition-o-philia:
the somewhat traditional practice of putting lots of separate partitions
on a system. but for 3 disks, linux MD has a nice mode where each block
is stored twice. so you get 2/3 space efficiency and potentially better
> It works, and you do get HA, but performance is not good. I'm now simplifying
> and upgrading the systems by fitting a 3ware 8006-2 hardware RAID1 controller
my experience with old 3ware boards was quite poor performance - much
slower than MD. >= 95xx are respectable, though.
> One thing you need to bear in mind in relation to HA is that software RAID
> does not support hot-swap - That's why I chose the 3ware 8006-2, which is not
> very expensive. It doesn't automatically detect new disks and rebuild the
> RAID, but it does support hot-swap and has a web GUI:
MD software raid certainly can support HS - it's mainly a feature of the
controller. (this is not to say that most controllers do HS well.)
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