Tuesday, February 13, 2007 10:56 PM lawrenso

SAN Disk Performance and configuration

Hi All,

 Well here I am - my first blogCool . It was a post from GrumpyOldDBA that decided me to join and start blogging.

The link to it is here


 It is not the whole document, but the comment right at the bottom in relation to SAN configuration.

I am a contract DBA and earn my crust on several different types of contract work, from pure support (pays the bills) through to Project work. I also get assignments for going to customers sites to carry out performance tuning on their systems.

What I have found repeatedly is the number of companies that have swallowed the Salesman's words, invested in a SAN and then have loaded all their systems onto it. More times than not, the disks are allocated to a RAID 5, with logical disks carved out for each system. They look at me funny when I start by issuing a disclaimer saying that for enhancements and recommendations that I make, the SAN will be an issue unless they are prepared to rip it apart and start again. Funny, nobody has taken me up on that offer yet!

 There are other issues with using SAN's. One previous customer had really bought into the SAN setup, running Web Servers, Databases, Mail, in fact, everything in the server room was connected to the SAN. Now, fortunately for them, their databases were not heavily used, with a low amount of transactions (just to clarify, this assignment was just giving backfill DBA cover), and they were not experiencing any performance issues in the area of the databases.

But what they were suffering from was Availability issues. I started this section by stating that they had bought into SAN's in a big way. Even going as far as having all the machines boot from the SAN. This is what I call "putting all you eggs into one basket". It ran lovely, but then, all of a sudden, everything disapeared. Everything went down! This then continued to happen 3-4 times a week. They had no way of troubleshooting the problem because all their servers booted from the SAN, so logs and everything were on the SAN, and this had dissapeared!!

When my contract was over, they were still having this issue and were testing updated drivers with the manufacturer of the SAN.

I hope they learn't their lesson with this. As I said above, I call this "Putting all your eggs in one basket", not because of what it appears to do, but because, when that basket is dropped, all you eggs get smashed.Geeked


# re: SAN Disk Performance and configuration

Wednesday, February 14, 2007 1:03 PM by tonyrogerson

Amazing; this is what happens when people ignore what is staring them in the face and totally absorb the marketing hype that go with SAN's.

Great as file server storage but naff all use for database work unless you are willing to spend large in which case you'd have probably save substantial amounts of money redeveloping the app using more service orientation and therefore commodity kit.

Good luck with the blog - great to see you on board!