FastT200 write performance problem

Archived from groups: comp.sys.ibm.pc.hardware.storage (More info?)

De: "Emmanuel Bouchard" <manu@saguenay.dhs.org>
Objet: FastT200 write performance problem...
Date: 30 août, 2004 20:31

Hi all..

I'm quite new to the SAN's world...

Few months ago, we bought a FastT200 SAN from IBM. We connected it to an
IBM Xseries 345 Server. (Windows 2000 SVR SP4)

We have 2 RAID controllers ont the FastT200 and they're both connected to a
2Gb FC switch. (So is the XSeries server)

The SAN worked fine for months...

The setup is simple:

10*73Gb disks...
1 RAID-5 Array
1 LUN assigned to the XSeries 345 Host Card (about 550 Gb)

Few weeks ago, we started having problems... Everytime we have lot of write
IO's on the SAN, the server stops responding for few seconds to few minutes.
The write performance is really poor (about 3MB/sec) compared to the read
performance (about 16MB/s).

I know that RAID-5 is real bad for write performance. Since the FastT200
has write caching enabled (128 mb), is'nt it supposed to be better?? And...
Is it normal that my Windows 2000 Server stops responding to the network
when those write IO's take place??

I have all the latest drivers and firmware for the FastT200...

I tried the Microsoft fix (#332023) but it's not better...

I really don't know what should I do next.. Should playing with the Segment
Size (It is actually set to 64 kb).

Also, when I look at the cache settings in the Storage Manager, I see that
write caching is enabled, but not currently active... How can I activate
it??

I really need some help..
Thanks.

Emmanuel Bouchard