sql server data warehouse:
did you hear "Jéjé" <willgart_A_@hotmail_A_.com> say in
news:eEqMmS7iFHA.1044@tk2msftngp13.phx.gbl:
[quoted text, click to view] > Hi,
>
> I have some issues with a server which is connected to a slow SAN.
> the iometer utility says:
> SAN= 260io/sec - 8mb/s (32kb block read/write)
> Local C:=500io/sec - 15mb/s (32kb block read/write)
>
> To try to improve my loading proces, I have added some files on the
> local C. So my staging area database use 2 files 1 on the SAN the
> second on the C: in some loading steps there is 50% of improvement
> while there is a little loss in other steps.
>
> with this change I see some waittype LATCH_EX with the
> waitresource=PARALLEL_PAGE_SUPPLIER information.
>
> I have a big update statement on a 2millions rows table, and the
> waittype is PAGEIOLATCH_SH
>
> does it because 1 disk has a better throughput then the second?
> Can I ask SQL Server to read/write 2 blocks on the local drive and
> only 1 block on the SAN?
>
> I have no access to the configuration of the SAN. (but we ask the
> administrator to do something!!!)
>
> thanks for your comments.
>
>
>
Brian Moran covered it off in SQL ServerMagazine in July 2004:
http://www.windowsitpro.com/Articles/Index.cfm?ArticleID=42902 &DisplayTab=Article
latches are lightwieght locks (BOL covers latches - badly) and if you have
quite a few nonzero waittime pageiolatch_sh SPIDs you may have a disk
bottleneck (identifies connections waiting for SQL to read a page from disk
into RAM)
other considerations here are what level of RAID are you using and are the
files in separate filegroups (could cause more harm than good). might be
well worth your while to pick up Kalen Delaney's "Inside SQL server 2000"
(chapter 4 specifically has some usefull info for you)
</end commercial> ;)
--
Neil MacMurchy
http://spaces.msn.com/members/neilmacmurchy http://spaces.msn.com/members/mctblogs
