> Peter Childs wrote:
>
> On Mon, 20 Oct 2003, Shridhar Daithankar wrote:
> >
> > A fast HD with a good RAID controller. Subject to budget, SCSI are
> > beter buy than IDE. So does hardware SCSI RAID.
> >
> I hate asking this again. But WHY?
>
> What SCSI gain in spinning at 15000RPM and larger
> buffers. They lose in Space, and a slower bus. I would like
> to see some profe. Sorry.
They win it, easily, on random disk accesses and mixed reads and writes.
And the bus is, much, faster not slower.
> IDE Hard Disk 40Gb 7200RPM = 133Mbs = 50UKP
> SCSI Hard Disk 36Gb 10000RPM = 160Mbs = 110UKP
>
> Is that extra 27Mbs worth another IDE Disk. and while
> you can get bigger faster SCSI disks prices go through the
> roof. Its no longer RAID but RAED (Redundant Array of Expensive Disks)
You're looking at the BUS speed, not the actual speed the disk achieves.
My guess is that that SCSI disk is, on some fields, twice as fast as the
IDE and on average 10-30% faster.
> My advise not that I've got any proof is that the money
> is better spent on a good disk controller and many disks than
> on each disk.
This havily depends on your setup and tasks.
- SCSI has a (supposedly) better lifetime, due to (much) better disk
components.
- SCSI disks are designed for servertasks (many random accesses) and
have their queue-management (better) tuned for that. This also applies
to mixed reads and writes.
- SCSI disks have, often, smaller and thicker platters which can spin
more stable and at higher RPMs.
- The SCSI bus allows all the disks to operate at maximum speed (as far
as the PCI-bus can handle it of course), while the IDE bus is shared
among both disks.
- SCSI allows more disks and longer cables on the same controller.
Anyway, you don't need all those advantages all the time, since the
major disadvantage is of course the pricetag.
For simple backup solutions (many storage for with reasonable
performance and an acceptable price), IDE is quite good in RAID5 orso.
For a high performing Database, you really want to look into a RAID
setup with scsi (or at least WD Raptor IDE disks or something like
that).
> In short if you have money to burn then by all means
> get SCSI but most people are better of spending
Also if you don't have money to burn, but simply need the higher
performance (which is really there) for, for instance, the random disk
accesses.
Best regards,
Arjen
