Re: opinion on disk speed

On Thu, 8 Dec 2005, 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.
>
> My only concern is the 10kRPM vs 15kRPM. The advantage of the 10k disks is
> that it would come from the same vendor as the systems to which it will be
> connected, making procurement easier.

if space isn't an issue then you fall back to the old standby rules of
thumb

more spindles are better (more disk heads that can move around
independantly)

faster drives are better (less time to read or write a track)

so the 15k drive option is better

one other note, you probably don't want to use all the disks in a raid10
array, you probably want to split a pair of them off into a seperate raid1
array and put your WAL on it.

David Lang