Re: IO Bottleneck

Write cache could remorve 1 IO operation out of 4 for RAID 5. Instead of
defining write performance as P*N'/4, you could descibe it as P*N'/3.

For your 4 drive RAID 5 array using 10K drives, your current write
performance would be something like 85*3/4 or 61 IOPS. Adding the write
cache could, depending on controller architecture, change that to 85*3/3 or
85 IOPS. I doubt that, in practical terms, it would make much difference.



"Ariel" <Ariel@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote in message
news:C812D79F-A273-4DA4-908A-79514F8E5096@xxxxxxxxxxxxxxxx
John:

Thanks for your response. The way you describe is exactly how I would
design
a new server. However, this is our only exchange production server, and I
need to improve performance as much as possible without reinstalling it.

So, would adding the battery backed write cache improve performance in a
significant way? And would I be better of moving something else to the
logs
disk, say, the smtp queue or temp dirs?

"John Fullbright [MVP]" escribió:

At a minimum, you should have a mirror for the OS, a mirror for the logs,
and a mirror (or RAID 10) for the databases. I'd hazard a guess that the
write times on the the RAID 5 array far exceed 20ms.


"Ariel" <Ariel@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote in message
news:F0839239-546B-4AA9-8B55-5B0E7A4DC986@xxxxxxxxxxxxxxxx
I have recently become the administrator of an Exchange 2003 Server.
These
are the server specs:

HP Proliant DL380 G3
Dual Xeon 2.8GHz
2GB RAM
Smart Array 5i Controller with 64MB and read-only cache
4 x 300GB Ultra320 10K Hard Drives in a RAID 5 array

I have been assigned the task to investigate a possible bottleneck,
since
users were seeing the RPC dialog frecuently. I ran the Performance
Troubleshooting Analyzer, and of course, the results indicated a disk
bottleneck.

The server has room for 2 more hard drives. I tried adding a 73GB disk,
and
using it for the database logs, then ran the PTA again, and now the
report
says that I have a disk bottleneck in all the roles that remained on
the
primary array.

I am going to add another 73GB disk to make a RAID 1 array, and move
the
logs anyways, but I was wondering if I should transfer another role to
that
new volume.
I am also considering buying an upgrade for the controller to add 128MB
of
battery-backed write cache, if it would help.

I would appreciate any advice you have to offer.

Regards,

Ariel.





.

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