August 13, 2010 at 7:11 am
We have an HP EVA SAN which was purchased for our SQL environment. Normally the SAN admin would give me three LUNS for my SQL servers. He now only gives me two LUNS so that the LOGs and TempDB can share the same drive. I asked him why and he stated the drives all share the same 200 spindles so the third drive is a waste of time. He said that you actually need seperate SAN (heads) controllers to make a difference.
I thought you get an extra OS thread for each LUN, yes, no, maybe?
Does anyone have the Pros and Cons of the tempDB and Logfile sharing the same LUN?
Windows 2008 Enterprise x64
SQL 2008 Enterprise x64
Sharepointpoint 2010 is the app
Thanks
August 13, 2010 at 7:16 am
get together with your SAN guy and tell him you need your database log and tempdb IO activity separated and what is he going to do to provide that for you?
---------------------------------------------------------------------
August 13, 2010 at 8:38 am
Thanks for the reply but I need something I can take with me to justify the seperate LUNS for tempDB and Logs.
August 13, 2010 at 8:47 am
Brent Ozar is the expert (or one of them) you can check out this sectin on his blog for documentation to backup your request: http://www.brentozar.com/sql/sql-server-san-best-practices/[/url]
You might also Bing/Google for Denny Cherry who also has a lot of knowledge on SAN configurations with SQL Server. He has articles on IT Knowledge Exchange: http://itknowledgeexchange.techtarget.com/sql-server/[/url]
Then just also Bing/Google for something like "SQL Server SAN configuration" and anything with Microsoft or MVP names tied to the author should more than suffice.
Shawn Melton
Twitter: @wsmelton
Blog: wsmelton.github.com
Github: wsmelton
August 13, 2010 at 8:48 am
you can justify by giving the data like :-
1) how important your database performance and role fo tempdb in this.
2) performance comparison by putting the temdb log on another drive and putting it to same with other db dirve.
3) if my templog keep increasing by anyhow and if it reside on same drive where other database file exists then it will make critical impact to performance
4) If templog will be fillled up then it will stop sqlserver if it not get cleared.
5) How frequent the user database accessing the tempdb
----------
Ashish
August 13, 2010 at 9:05 am
Grasshopper - good lick. They are mimicking what the sales rep is telling them. What took a looooooooong time to prove was that the pools need to be seperated into RAID 10 and RAID 5/50 areas. Then the luns need to be created so that your tempdb/t-logs go to the RAID 10 pool, and the data goes to the RAID 5/50 pool.
Now, if your database is a very busy OLTP database, you can also benefit by partitioning the database into seperate segments, placing each on a seperate logical drive on the SAN. This will cause SQL Server to use multiple threads to access the data, even though it is still across the same sppindles. This is an internal working of SQL, and can be monitored with tools like SQL Sentry or Spotlight on SQL from Quest Software.
Ideally, if the database(s) are very busy, you can improve performance even more by moving tempdb off the SAN and onto it's own physical drives.
It is great to say that the more spindles that you spread the files across, the better the performance, but there is a point of saturation, where the heads are working harder and harder to keep up with the data being transferred.
Good luck.
Steve Jimmo
Sr DBA
“If we ever forget that we are One Nation Under God, then we will be a Nation gone under." - Ronald Reagan
Viewing 6 posts - 1 through 5 (of 5 total)
You must be logged in to reply to this topic. Login to reply