Hello All,
An issue has been brought to my attention in regards to NVRAM and cache.
Also I have been considering snapshot mode v8.6S and thanks for the
information on that. Thanks to the following individuals: Pete Lindsey, Udo
de Boer, and Robert Sandford. The responses to my questions are verbatim.
Pete Lindsey
The NVRAM (non volatile random access memory) on an HSG80 is 128k and not to
be confused with your cache (which is 64 to 512mb). NVRAM holds your
configuration information which will be good for weeks if not months. Cache
will flush depending on your configuration (default is 10 min). You can
also use the cli and issue the following command "config save". At this
point the you could feel safe in knowing the configuration in its entirety
is saved to the controller. (to restore the configuration use "config
restore"). Alternatively, at the addition of the storage set, you could
append the "save" parameter which would store that units configuration to
the drives themselves (will cost you a minute amount of drive space). The
disks themselves could be put in another controller and you could restore
the functionality of the unit by simply re-adding the set). As far as
upgrading to ACS 8.6, I aplaud your decision to do it off hours, as the
upgrade itself is fairly bullet proof... its not fool proof, (I have heard
horror stories) So when your ready, depress the reset button of one
controller, while holding it in, replace the 8.5 card with the 8.6 card.
Wait for the controller to complete boot (2-3 minutes top) Using the CLI
issue a "show this" command plugged into the controller you just upgraded,
as long as all looks Kosher, repeat the process for the second controller in
the pair. As far as the Dimm configuration, I have heard a lot of gripping
about compaqs drop of the support for the 32mb dimm. I understand the
reason for the gripe, but I also understand compaq's position... (which I
don't think they have made clear for obvious reasons) The performance of a
32mb HSG80 is horrible, (specially when Max Cache xfer size is left alone
and Chunksize is left alone) at 32mb with a chunk size of 512 (256kb) you
only have 128 pages of read/write in cache... thats right!!! only 128 TOTAL
read/writes are cached. Your cache hits are through the floor with just
about any application. When you change the chunk size to something that
more closely represents your storage medium (like 16blocks or 8K for oracle)
then you start having some reasonable cache hits (with 32mb its still only
4000 total cache read/writes, but when you up it to 512 you get closer to
64000 cache read / writes which brings your cache hit % into the respectable
90's as aposed to the 20's or lower)
Udo de Boer
One thing about cache size in an HSG80. The maximum size cache won't give
you
much performance gains while running application that cache themselve. Like
Oracle or if you have a system with a lot of free memory. The advfs cache
will
do the work. The large cache size is only usefull on systems that do no
caching
themselves. Your very expensive memory can be put to better use inside the
system most of the times. Than cache access is not done over fibre channel
but
instead to local ram. Also enabling write back cache can enhance
performance.
But can also give disk errors when the batteries runout and the system has
been
crashed. And for this 128mb is enough.
Robert Sandford
I wanted to point out some things before you attempt this. V8.6F firmware
requires at least 256MB of cache memory. However, if you ever go to
snapshot mode (V8.6S) you will need 512. You can not upgrade one controller
at a time with memory. If you attempt to bring up a controller with a
different amount of memory you will get a controller misconfiguration error
and cause more problems. The entire SAN and servers will need to be
shutdown for memory upgrade. I would recommend upgrading to 512 and set
your cache to be mirrored.
If you are not running in Multibus failover mode then I would consider
doing this as well.
Also when you are upgrading your firmware it would be better to shutdown
your servers as well. You have to run FRUTIL from the HSG80 controller to
upgrade, you cannot simply remove the PCMCIA card and put in the new
version. For the exact procedure I will dig it up because I just did it.
When you run FRUTIL it will quiesce the controllers and basically all the
servers will temporarily lose access to the disks on your EMA. You could
risk ADVFS corruption if one of your disks was in a middle of a write.
Any time you bring down the controllers you should follow the procedure
on shutting down your cache batteries. It is not good draining them.
As for the CLI. The errors sometimes will be buffered and keep repeating
after every command you enter. You can fix this by entering "clear cli".
Thanks for the help!
Kenway Lee
Systems Engineer
IMPAC Funding Corp.
(949) 475-3934
klee_at_impaccompanies.com
Received on Thu Aug 16 2001 - 14:48:37 NZST