[Beowulf] RAID for home beowulf

Skylar Thompson skylar at cs.earlham.edu
Sat Oct 3 10:51:57 PDT 2009

Tomislav Maric wrote:
> Hi everyone,
> I've finally gathered all the hardware I need for my home beowulf. I'm
> thinking of setting up RAID 5 for the /home partition (that's where my
> simulation data will be and RAID 1 for the system / partitions without
> the /boot.
> 1) Does this sound reasonable?
It depends on your workload. RAID5 is good for large sequential writes,
but sucks at small sequential writes because for every write it has to
do a read to compare parity.

> 2) I want to put the /home at the beginning of the disks go get faster
> write/seek speeds, if the partitions are the same, software RAID doesn't
> care where they are?

I don't think this will buy you much performance. There probably is a
measurable difference, but I don't think it's enough to worry about.

> 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?

Sure, but /boot is actually trivial to mirror. Just make sure your boot
loader is on each disk in the mirror and that each disk is partitioned
identically, and all you have to do if a drive dies is change the device
you boot off of if a drive dies.

> 4) I've read about setting up parallel swaping via priority given to
> swap partitions in fstab, but also how it would be ok to create RAID 1
> array of swap partitions for the HA of the cluster. What should I choose?

Any swapping at all will kill performance. I would get enough RAM to
make sure you don't swap.

> I've gone through all the software raid how-tos, FAQs and similar, but
> they are not quite new (date at least 3 years) and there's no reference
> to clusters. Any pointers regarding this?

If you're using a Red Hat-based distro, kickstart can handle software
RAID. I don't know about other distros though.

-- Skylar Thompson (skylar at cs.earlham.edu)
-- http://www.cs.earlham.edu/~skylar/

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