[CentOS] Painfully slow NetApp with databas

nate centos at linuxpowered.net
Thu Nov 6 12:46:18 UTC 2008


Mindaugas Riauba wrote:

>   NetApp support is claiming that such performance is normal. Somehow
> I do not believe that 2007 model should deliver such XXth century
> performance levels. :)

How many disks, what RPM are they running at, what I/O block size
is being used and what protocol (NFS/iSCSI/FC) is being used?

Checking an Oracle DB I used to run it averages 7k I/Os with
spikes to 59k. For a 10k RPM disk, 7k I/O size means roughly
800kBytes/second before latency starts to become an issue depending
on the controller type. Really high end controllers can
go up to about 1,312kB instead of 800kB. The array reports
Oracle is using an average of 985 kBytes/second with spikes to
28MBytes/second.

A MySQL DB I used to run averages 41k I/Os with spikes up to
333k. For a 10k RPM disk 41k I/O is 4500 kBytes/second. The
array reports MySQL using an average of 3200 kBytes/second with
spikes to 34.1MBytes/second.

The array throughput numbers include benefit from the disk
cache, while the raw spindle performance assumes no cache
(or "worst case" performance).

Both of those are connected via Fiber channel so performance will
be quite a bit higher than that of NFS or iSCSI.

So the numbers your seeing could be perfectly reasonable as
NetApp suggests depending on what the exact workload is and
your array configuration. For the workload you should look
to the array for statistics, I'm not too familiar with NetApp
arrays but I assume they offer a wide range of statistics,
hopefully I/O size is among them as that is the most critical
to determine throughput.

The array running the above databases is a system running 40
10k RPM disks with the data evenly distributed across all
spindles for max performance. The array also is host to about
25 other systems as well.

NetApps certainly aren't the fastest thing in the west but
given your performance levels it sounds like you don't have
many disks connected and are limited by the disks rather
than the controller(s).

Most low end arrays don't offer the level of visibility that
the enterprise ones do.

On that note I'm getting a new 150TB array in today, pretty
excited about that. 3PAR T400 virtualized storage system.

nate




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