[lug] Promise Vtrak performance

[Rob Nagler]

We have two Promise Vtrak 12110 enclosures with 12 x 500MB SATA drives
configured with RAID5 as a single array and 3 logical drives (2 x 2TB,
1 x 1TB).  Performance is abysmal now that we've been using this set
up for a while.  We are only using one of the 2TB logical drives; the
other two drives are mostly empty.

We are rsyncing nightly for backups from a variety of machines.  At
first this was working just fine.  As the file system grew to
hundreds of inodes, rsync got slower and slower.  I don't think it is
rsync as the data mix on the machines we are backing up is not that
different.  The rsync is hung in a device wait on the backup
machine pretty much any time I look.

The one complication is taht we are linking with cp --archive --link
to keep historical copies.  This means static inodes are being
reference hundred or so times.  Static inodes make up most of the data
mix so I suspect there's some behavior relating to how ext3
distributes inodes and how the vtrak distributes its data.

Even simple operations, like rm -rf on old backups or du, take hours
and sometimes days to run.

I have seen references on the net to slow performance on the Promise
enclosures (which are Linux boxes, btw).  Promise has asked for lots
of information, but they haven't provided any answers.

The performance is abysmal on both RH7.2 on RHEL4.5 (CentOS).  It
doesn't matter if the machine is busy or idle.  It can be doing
nothing, and a du will not complete in an hour, when I think it should
(and does in similar mixes on much slower machines).

Rob