[wplug] Hardware RAID tuning
Martin James Gehrke
martin at teamgehrke.com
Tue Jun 14 14:22:02 EDT 2011
Could you be more specific about your backup mechanism? Are you doing a full
backup? Over the network? Using NFS/SCP/RSYNC/RDIFF?
1. any indiciation why the drop from 40MB/s to 2MB/s
2. is the backup online? are jobs writing while you are reading?
Sequential read should get good performance on a raid5, if you are writing
and reading at the same time, one will suffer (usually writing).
any benchmarking with IOZone?
what is the controller cache size?
why raid5? We've completely phased out raid5 in favor of raid6.
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On Tue, Jun 14, 2011 at 2:00 PM, Matthew Zwier <mczwier at gmail.com> wrote:
> Hi all,
> I'm the systems administrator for a relatively small (~20 nodes, ~320
> cores) scientific computing cluster with relatively large (20 TB)
> storage needs. We have a couple of RAID5 arrays on a Dell PERC/5E
> (aka LSI MegaRAID) controller , both running XFS filesystems, and
> while performance is generally acceptable, it appears I can't get a
> backup in under five days for our 11 TB array. That leads me to a
> couple of questions:
> 1) That translates to about a 40 MB/s sustained read, with frequent
> lengthy drops to around 2 MB/s (this using xfsdump into /dev/null, for
> the moment). For those of you with more experience than I...is that
> typical performance for a filesystem dump? Pleasantly fast?
> Unacceptably slow?
> 2) Does anyone know of documentation about how to go about tuning an
> on-line hardware RAID array in Linux, specifically for file service?
> About all I can find are discussions about how to optimize MySQL
> performance, or tips on what parameters in /sys to tweak while piping
> zeros directly to /dev/sdb using dd, and the like. I can't find any
> documentation on how various hardware/kernel/filesystem parameters
> interact. The three-way optimization problem among RAID controller
> settings (i.e. read-ahead), disk- and controller-specific kernel
> settings (TCQ depth, read-ahead), and I/O-scheduler-specific settings
> (noop vs. deadline vs. cfq, queue size, etc) is just killing me.
> Matt Z.
> wplug mailing list
> wplug at wplug.org
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