Symmetrix performance problem - too easy?

[Ian Vaughan]

Howdy,
Our overnight batch work (HP-UX 11,Progress DB) takes 50% longer to complete since we moved to another Symmetrix. I have today found out that we are now using the universally disliked 181GB 7200rpm disks whereas we had 73GB 10K rpm disks before.
With all other things being equal (same no of spindles other hardware same or better)- can this really be down to the average seek time on the disks at the back end? Even after all the claims that EMC make about their cache and their clever prefetch algorithyms??? The data is pretty random when I come to think about it....
Anyone else taken a performance hit with these 181Gb disks on an XP or another array?
TIA
Ian

[Stuart Abramson_2]

Ian:

We have some in our Symm 8430, but we haven't had any problems. All workloads are different, however.

We are now buying the 146 GB drives to fill out the frame however. Why take any chances.

But, you don't know it's the 181 GB drives. You moved to a different frame and other variables might have changed. You might have the indexes and data tables on the same physical disk, or some such problem. Have you looked into that? Do you use BCVs? Is the RAID the same? What was the old model; what is the new model? Do you have path failover, etc. Are the number of paths the same? etc, etc, etc...

Stuart

[Ian Vaughan]

Hi Stuart,
We too are looking at moving the app to a number of the 146GB disks and leaving the 181's for our BCV's and data storage. We are working with EMC to find out where the "hot-spots" are on the frame and see if we can stagger our batch jobs. Ta for the input.

[Massimo Bianchi]

Hi,
i had some performance experiece with prevoius versione of the frame, due to the phantoms track and to the algoritm used.

Is the firmware revisione the same ?

In another situation i had the same 50% performance problem, because the FS was initialized with a different block size.


When using the default block size for that lvol (8k) we had a 50% impact than when using a forced block size (of 1k).

I think you should also give that some chance.

Massimo