Re: opinion on disk speed

On Thu, 2005-12-08 at 11:52 -0500, Vivek Khera wrote:
> I have a choice to make on a RAID enclosure:
>
> 14x 36GB 15kRPM ultra 320 SCSI drives
>
> OR
>
> 12x 72GB 10kRPM ultra 320 SCSI drives
>
> both would be configured into RAID 10 over two SCSI channels using a
> megaraid 320-2x card.
>
> My goal is speed. Either would provide more disk space than I would
> need over the next two years.
>
> The database does a good number of write transactions, and a decent
> number of sequential scans over the whole DB (about 60GB including
> indexes) for large reports.

The STR of 15k is quite a bit higher than 10k. I'd be inclined toward
the 15k if it doesn't impact the budget.

For the write transactions, the speed and size of the DIMM on that LSI
card will matter the most. I believe the max memory on that adapter is
512MB. These cost so little that it wouldn't make sense to go with
anything smaller.

When comparing the two disks, don't forget to check for supported SCSI
features. In the past I've been surprised that some 10k disks don't
support packetization, QAS, and so forth. All 15k disks seem to support
these.

Don't forget to post some benchmarks when your vendor delivers ;)

-jwb