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

[ Post a follow-up to this message ]

HI

did you ever heard about IO Queue Depth and IO Queue´s?
All OS Systems open a Queue for all Disk Drive that they can read or write.
If you have 1 Drive with 550 GB you have only one IO_Queue to the complete
Space.
If the Queue is full, your OS is waiting to put the next IO into the Queue.
If you have 10 virtual Drives configured in yout Fast-T about 55 GB your OS
think
it has 10 Disks and open 10 IO Queues.
for Example:

1   IO_Queue = 8 SCSI Commands
10 IO_Queue = 80 SCSI Commands

I am not an Expert about Windows, if you find a value like "Disk Queue
Depth"
go with the value up or split the disks at the Fast T and stripe the disks
with the windows volume manager together
(watch out --> Data loss).

This can be one fact about your performance problem, other facts can be bad
cables (often!!!), bas SFP´s,
or simply that the Fast-T is overloaded.
How many IO´s did you produce?

Stefan


"Emmanuel Bouchard" <manu@saguenay.dhs.org> wrote in message
news:CFPYc.50270$E5.1270280@weber.videotron.net...
> 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
>
>
>
>

[ Post a follow-up to this message ]