Matt, writing multiple concurrent streams to the same set of disks may
be hurting performance. One at a time may yield better results.
I'm in the process of building out some staging servers myself for nbu
5.1 - been doing a bunch of bonnie++ benchmarks with various configs
for Linux using a sata 3ware controller.
On fedora core 3 (I know it's not supported):
Raid5, 5 disks I got ~30MB/sec writes & 187MB/sec reads. Raid 50 with
striping over 3 4-disk raid5's got 49MB/sec writes, 120 MB/sec reads.
For raid0, w/10 disks, got a nice 158 MB/sec writes, and 190MB/sec
reads.
I'm partial to raid5 for high availability even with poor write
performance.. I need to stream to lto3, which tops out at 180 MB/sec.
If I went with raid0 and lost a disk, then a media server would take a
dive, backups would fail, and I'd have to figure out what data failed
to make it off to tape. I'm not sure how I'd reconcile a lost dssu
with netbackup. If I wanted to to use the dssu's for doing synthetic
fulls, then that further complicates things if a staging unit is lost.
Any thoughts on what the netbackup fallout might be on a dssu loss?
Even though it's not supported yet, I was thinking of trying out
redhat enterprise linux 4, but I'm seeing really horrible disk
performance (eg. 100MB/sec reads for raid5 vs the 187MB/sec on fc3).
Maybe I should try out the supported rhel3 distribution. ;-) I
don't have high hopes of that improving performance at the moment.
On 8/10/05, Ed Wilts <ewilts AT ewilts DOT org> wrote:
> On Wed, Aug 10, 2005 at 12:43:39PM -0400, Matt Clausen wrote:
> > Yet when I do a backup to disk, I see decent performance
> > on one stream (about 8,000KB/s or so) but the other streams will drop to
> > around 300-500KB/s.
> >
> > NUMBER_DATA_BUFFERS = 16
> > NUMBER_DATA_BUFFERS_DISK = 16
> >
> > SIZE_DATA_BUFFERS = 262144
> > SIZE_DATA_BUFFERS_DISK = 1048576
> >
> > and I see this performance on both the master server disk pool AND a
> > media server disk pool. The master server is a VxVM concat volume set of
> > 3x73GB 10,000RPM disks and the media server is an external raid 5 volume
> > of 16x250GB SATA disks.
>
> I don't believe you're going to get good performance on a 16 member
> RAID5 set of SATA disk. You should get better with a pair of 8 member
> raid sets, but SATA is not fast disk and large raid 5 sets kill you on
> write performance. If you're stuck with the SATA drives, configure them
> as 3 4+1 RAID5 sets and use the 16th member as a hot spare. You'll have
> 3TB of disk staging instead of about 3.8TB but it will perform a lot
> better.
>
> --
> Ed Wilts, Mounds View, MN, USA
> mailto:ewilts AT ewilts DOT org
> _______________________________________________
> Veritas-bu maillist - Veritas-bu AT mailman.eng.auburn DOT edu
> http://mailman.eng.auburn.edu/mailman/listinfo/veritas-bu
>
--
-Tim
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