<div>We are currently running OLTP on and Ibm P570 aix 5.3 attached to a
DS4500 san. We currently have 36g 15k drives, Fiber Channel disks in
there.</div>
<div> </div>
<div>We are running out of space, and drawers. Our sales people are
telling us that we should move to 146g 15k rpm drives.</div>
<div>The supposed specs on those drives, from an ibm white paper
are:</div>
<div>3.5ms to read, 4ms to write, max sustained transfer rate
58-96mb/sec.</div>
<div> </div>
<div>The funny thing is, they have the same performance rates whether the
drive is 73g or 146g.</div>
<div>We have been under the impression that the bigger a drive is, the
slower the average IO will be, due to the fact that the head has to do
more moving around to get a bigger part of the data.</div>
<div> </div>
<div>So my questions basically are:</div>
<div>1) Is our premise correct, or is IBM correct in saying that we will
not suffer a performance decrease by moving to bigger drives ?</div>
<div>2) Has anyone done any testing on these ? I wouldn't be sure where to
begin to do my own benchmarking, without having a totally isolated system.
Or am I just reading too much into this and should just buy the bigger
disks.</div>
<div>3) What am I missing here ?</div>
<div> </div>
<div>Any advice is appreciated.</div>
<div> </div>
<div>Thanks,</div>
<div>Floyd</div>
<div> </div>
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We are currently running OLTP on and Ibm P570 aix 5.3 attached to a DS4500
san. We currently have 36g 15k drives, Fiber Channel disks in there.
We are running out of space, and drawers. Our sales people are telling us
that we should move to 146g 15k rpm drives.
The supposed specs on those drives, from an ibm white paper are:
3.5ms to read, 4ms to write, max sustained transfer rate 58-96mb/sec.
The funny thing is, they have the same performance rates whether the drive
is 73g or 146g.
We have been under the impression that the bigger a drive is, the slower
the average IO will be, due to the fact that the head has to do more
moving around to get a bigger part of the data.
So my questions basically are:
1) Is our premise correct, or is IBM correct in saying that we will not
suffer a performance decrease by moving to bigger drives ?
2) Has anyone done any testing on these ? I wouldn't be sure where to
begin to do my own benchmarking, without having a totally isolated system.
Or am I just reading too much into this and should just buy the bigger
disks.
3) What am I missing here ?
Any advice is appreciated.
Thanks,
Floyd
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Content-Transfer-Encoding: 8bit
<div>We are currently running OLTP on and Ibm P570 aix 5.3 attached to a
DS4500 san. We currently have 36g 15k drives, Fiber Channel disks in
there.</div>
<div> </div>
<div>We are running out of space, and drawers. Our sales people are
telling us that we should move to 146g 15k rpm drives.</div>
<div>The supposed specs on those drives, from an ibm white paper
are:</div>
<div>3.5ms to read, 4ms to write, max sustained transfer rate
58-96mb/sec.</div>
<div> </div>
<div>The funny thing is, they have the same performance rates whether the
drive is 73g or 146g.</div>
<div>We have been under the impression that the bigger a drive is, the
slower the average IO will be, due to the fact that the head has to do
more moving around to get a bigger part of the data.</div>
<div> </div>
<div>So my questions basically are:</div>
<div>1) Is our premise correct, or is IBM correct in saying that we will
not suffer a performance decrease by moving to bigger drives ?</div>
<div>2) Has anyone done any testing on these ? I wouldn't be sure where to
begin to do my own benchmarking, without having a totally isolated system.
Or am I just reading too much into this and should just buy the bigger
disks.</div>
<div>3) What am I missing here ?</div>
<div> </div>
<div>Any advice is appreciated.</div>
<div> </div>
<div>Thanks,</div>
<div>Floyd</div>
<div> </div>
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