From: Osma Ahvenlampi <[EMAIL PROTECTED]>
Suppose I had a system equipped with, say, 4x 9GB SCSI disks that I'd
like to set up as a fairly generic server system. Conventional server
setup wisdom says to partition /, /usr, /var, /home and perhaps
/var/spool separately. However, how does the RAID-5 subsystem perform
The primary reason for partitioning is too prevent overflowing the
root filesystem, especially in the case of /var. /usr is separate
since it tends to be shared NFS in large installations, /home is
similar for NIS based systems. With RAID, conventional thinking is a
bad idea. The only other reason that springs to mind for partitioning
is installation of other Operating Systems.
when multiple md devices are configured to span the same physical
disks? Obviously, all volumes benefit from redundancy, but let's think
about the performance side only for now (for that reason, perhaps it
would actually make more sense to compare striped md's to dedicated
disks..) Immediate thought is that number of seeks may increase,
resulting in more time lost to seek times. On the other hand,
sustained bandwidth is greater for all volumes. Has anyone run
benchmarks to find out which is the more powerful factor?
I started this discussion once too a few months ago, the answer is "it
depends". You need to consider the purpose of the various filesystems
and the server purpose. You would need to find people running a
similar setup for a similar purpose to have a useful discussion.
For myself, I have 6 disks spread over a dual controller. One small
100 Meg disk is dedicated to swap, initrd boots and DOS. None of the
others are partitioned (yet), since I'm still tinkering around and
overflow threats are nil. The others are allocated to reduce head
movement for MY purposes. A pair of 1 G identical drives is the only
RAID set. Then one drive for the audio server and one drive for the
smb server. Nowdays I believe that the bandwidth loss due to seek
time overwhelms the increased bandwidth from RAID under heavy load.
Thus smaller (and more) disks are preferred (they can always be
RAID0ed to increase bandwidth) YMMV...and only your own performance
measurements will be truely useful.
The general rule from my setup appears to be, dedicate drives to
server processes.
