Re: SAN and Performance

Don't be fooled-- any interface between the CPU and the data storage has overhead. The key is to make sure the interfaces are fast enough that the overhead isn't noticable.

We went to SAN two hardware upgrades ago. It was a complex upgrade; as part of the upgrade we also installed a 2nd system at our 'downtown' location for disaster backup. We went with the V7000.

We had some 'interesting' startup issues, mainly because we were synchronizing to the DR site, and the configuration we chose was NOT the best one! We now use Change Volumes with Consistency Groups. Delay time to downtown is 30 minutes or less.

As far as speed-- the initial SAN had spinning disks. It was an impressive array-- 240 disks IIRC, but the impressive speed increase we were sold didn't happen. The speed wasn't any great improvement over the internal disk system we were leaving.

We then acquired a model ?820? flash appliance from IBM, which they had acquired when they bought Texas Memory Systems (?). Wow! That was the speed we were looking for. The 820 piggybacked on the V7000, and looked like another piece of disk (!).

Due to the extra space in the 820 we were able to use one of the nice features of the V7000- we made a flash copy of our production system and ran production backups from the copy. We decided to run an Option/21 backup every night! We had never done option 21s except prior to hardware or OS upgrades.

IIRC, migrating our data to the V7000 used some hardware magic-- the V7000 was attached to our old system, and the data was siphoned disk to disk. We didn't have to use a tape unload/load.

About a year ago we upgraded our SAN to a V9000 - all solid state memory. I like to say it's like 50 gazillion thumb drives stuffed in a little box! Physically, it's only about 6 or 8 rack spaces high, and 57 TBytes wide.

Conversion from the old to new SANs used more hardware magic-- connect both SANs to the system and let the data walk across. WOW! Best thing since sliced bread!!

Although that first transition was rough-- we were uneducated in what we were getting, and our business partner at the time was no farther along than we were-- the advantages of the SAN have let us simplify our backup processes.

Would we do it again? Yes, but only if the business partner and the folks handling the configuration and conversion know the hardware inside and out! Since that first conversion we've upgraded our business partner, and that 2nd transition was smooth!

--Paul E Musselman