Slow SCSI RAID5 Array...

  • Thread starter Thread starter NewMan
  • Start date Start date
N

NewMan

Hi,

I have a Dell 1600SC running Win2000 Server. This box has a PERC4/SC
RAID Card, and 3 x 73 GB SCSI 10,000 RPM drives configured for
Hardware RAID5.

When this server was originally deployed some 3 years ago, it was a
screamer. No complaints about disk access at all.

A few months ago, something on the O/S partition got corrupted and the
box would not boot to W2K Server, so I took it off-line. I ran just
about every disagnostic under the sun, including the DELL diagnotics.
Everything checks out OK. So, I nuked the "C:" drive and reinstalled
W2K server. Then I migrated the data back onto the allocated data
share.

This is when the problems started. For some strange reason, access to
the disk is now just painfully slow. I have googled myself to death,
and tried various things which have made marginal improvements. Still
TOO SLOW.

So I happen to have Thecus N5200 NAS Box configured with 5 x 320GB
7200 RPM SATAII Seagates in a RAID6 array.

I copied some of the data onto a test partition on the NAS box, and
tried to access it. Seemed nice and snappy!

So I downloaded a copy of IOMeter to see what the write speed were
like all round.

My local computer maxes out at 13 ms MAX for a "write". The NAS box
maxes out at about 18 ms. The W2K server maxes out a >1500 ms?????

WTF???

I was blaming some of this on the various client computers involved,
but these tests were done on my own machine which is running
perfectly.

So what gives???

Why on earth is the rebuilt server running so damn slow???

Any and all suggestions would be greatly appreciated!
 
Have you run the disk manufacturers diagnostics? Have you booted into
controller bios to check for errors?


--

Regards,

Dave Patrick ....Please no email replies - reply in newsgroup.
Microsoft Certified Professional
Microsoft MVP [Windows]
http://www.microsoft.com/protect
 
How is the array terminated? By drive or active terminator? Should be by
active terminator. Replace it.
 
GOT IT!

A poster on another forum driected me to this publication:

http://download.microsoft.com/download/e/b/a/eba1050f-a31d-436b-9281-92cdfeae4b45/subsys_perf.doc

As I said somewhere else, I had found a firmware update for my
PERC4/SC card. As near as I can tell, when the firmware was flashed
into the card, while it DID maintain the array information to permit
reboot, the flash appears to have reset the various options of the
card - most noteably the WriteBack Cache!

I looked at the Dell Open-Manage application, and it told me write
caching was disabled.

I had to reboot and press <ctrl>-m to get into the config screen for
the Perc4, then hunt around a bit.

Once the WriteBack Cache was turned on, and the server re-booted it is
back to its snappy self!

Speed tests for my local Sata run at max write of 13, and the Nas Box
at 18 ms, the server now measures about 15 ms!

I know the Perc4 has no battery option, but I have a beefy APC UPS
that can hold the server up for almost 45 minutes, and I have the
PowerChute software to allow an orderly shut-down - so I don't think
there is too much risk! ;)

This problem was really getting on everyone's nerves.

I had no idea that RAID-5 took such a nit on the disk write
operations. Thank God I have the right hardware to mitigate the risks,
and still get the performance.

Cheers
 
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