[Beowulf] RAID for home beowulf

Mark Hahn hahn at mcmaster.ca
Mon Oct 5 02:28:52 EDT 2009


> the other nodes are to be diskless.. I have separated these partitions:
>  /swap /boot /  /var and /home. Is this ok?

I don't believe there is much value in separating partitions like this.
for instance, a swap partition has no advantage over a swap file,
and the latter is generally more convenient.  separating /boot is 
largely a vestige of quite old bioses which could not do 48b LBA 
addressing (ie, deal with big disks.)  separating /, /var and /home
is largely a matter of taste:

 	- separate /home means that you can blast / and /var when
 	you upgrade or change distros.

 	- separating / and /var means that something like syslog or
 	mail can never fill up the root partition.  which is generally
 	not a serious issue anyway: if anything, this argues for putting
 	/tmp in a separate partition, but leaving /var inside /...

 	- more partitions (filesystems) means more time spent waiting
 	for disk heads to seek.  remember that write activity on any fs
 	(modern, journaling) requires some synchronous writes, and
 	therefore can't be lazy-ified or elevator-scheduled when you have
 	multiple partitions.

I think it's always a good idea to minimize partitions, though we can
probably argue about how many is best.  I suppose one factor in favor 
of separate, purpose-specific filesystems is that they might be split
into different raid levels.  for instance, /tmp might be raid0, perhaps
/var a >2 disk raid10 for write speed, and /home left on /, both under
raid6.  but given that you don't want multiple filesystems competing 
for access to the same disk(s), I'm skeptical of this approach...

in short, it's perfectly OK to use one big filesystem.  or you can just 
use the distro's default partitioning scheme.  in the end it's not going
to make much difference.

regards, mark hahn.
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