[SunRescue] Question about SSAs

[David Passmore]

On Fri, May 04, 2001 at 09:01:39PM -0400, Dave McGuire wrote:

>   On the subject of FCAL...I'm about to light up an A5100 on an Ultra30
> with a QLA2100.  I've never managed an FCAL-based system before, and
> the I/O performance of this system is going to be rather
> critical...can anyone offer any tips for performance tuning and/or
> monitoring?  The system is running Solaris7, with which I'm also
> somewhat unfamiliar...I'm a BSD guy.

I did an evaluation of A5200s vs. EMC Symmetrix last year; 10 fully
populated A5200s, 220 18GB spindles, vs 96 36GB spindles in the Symm with
8GB of cache.

The A5200 whipped the pants off the Symm in sequential and random write
performance, simply due to the virtue of having twice as many spindles. No
rocket science there-- if your workload is read-intensive, the A5x00s are
cake (and the only modern Sun storage I would use).

On both sequential and random write (8k) the EMC kicked the pants off the
A5200s, with one EMC spindle being worth roughly two A5200 spindles. This
was sustained I/O, not burst. However, for all writes the average service
time on the A5200s was pretty high, sometimes exceeding a second in heavy
usage.

If your workload is write intensive I would invest in a Fast-Write Cache
card, which is your basic prestoserve with 64MB of NVRAM on a PCI card. If
the access pattern is sequential this will give you double-digit gains, if
it is mostly random you might see a 2x gain in performance. In either case
you will see big gains in response time.

You'll want to set this in /etc/system:

set ssd_max_throttle = 250

This is the number of SCSI commands that the ssd driver will queue to the
HBA driver. If you exceed the maximum queue depth of the array you will
degrade performance. For Sun arrays, the maximum queue depth is 255. You
will probably never hit this wall on an Ultra 30, but it's something to be
aware of. 

Bigger block sizes with fibre channel are better, but not enough to really
matter one way or the other. With a fully populated array you likely won't
be able to push more than 30MB/s to it. 

For monitoring and general metric gathering I would recommend SEtoolkit:
http://www.setoolkit.com/

David