When the backend can't keep up with the frontend, the WP counts get high.

If you are seeing low WP counts along with poor write response times, I would suspect a frontend bottleneck.

it could be possible..

You are flushing your cache and you have low WP so your backend is good.

but you have High Write response time so your Frontends are not pushing enough data in cache or backend.

If you are seeing low WP counts along with poor write response times, I would suspect a frontend bottleneck.

i don't think i am following you. If i have very low wp counts why would i have very high write times in symmetrix (as seen in that chart)  ?

I was suggesting that the writes can't get into the system fast enough because you don't have enough FA resources.

Quincy,

i could be looking at it all wrong, please correct me. When i look at chart with "Sampled average write times", this is from FA perspective ..how long it took for it to send request to the system and get it back. So if write pendings are low, there is nothing sitting in cache ..why would FA wait for so long.

Thank you

I'm suggesting that you are writing to the FA faster than it can deal with the IOs, so it has to queue them.  I would suggest adding FA CPUs (not just ports) and see if the write response time gets better.

this device is mapped to four FAs ..you tell me ..but they don't seem to be busy to me (these are CPU stats).

could be, but if you look at "sample average write time (ms)" ..it stays very high for almost an hour.  These devices are configured for SRDF/S, what metrics can i look in Performance Manager to see if SRDF could have anything to do with that ?

No, they don't look busy over that sample interval, but what about during a one or two second sample?

We have seen many cases where writes burst for just a very short period of time, then stop.  During that short period of time they can overwhelm the front end causing high response times.

It still could be something else such as a SAN problem or slot contention.

we have a case opened but PSE kicked it back to local support and it takes local guys forever to setup STP and all that stuff. I am paying boat load of money for ECC/Performance Manager so trying to research myself as well. Thanks for suggestions so far.