Re: Recomended FS - Mailing list pgsql-general

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?

The duty cycle of SCSI drives is 100%.  The duty cycle of IDE drives is
around 30-40%.  Therefore one uses SCSI drives in mail and news servers
where disk access is more-or-less permanent.  IDE drives usually degrade
or fail faster under such load.

 From experience I have noticed that IDE drives that initially perform
at 30Mbyte/sec dropped to around 10Mbyte/sec after a year or so.

>     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.
>
> IDE Hard Disk 40Gb 7200RPM   = 133Mbs = 50UKP
> SCSI Hard Disk 36Gb 10000RPM = 160Mbs = 110UKP

On new servers doing a software RAID1 sync between two disks, I find the
following sustained transfer rates:

SuperMicro 6013P-i ATA 133 80Gb IDE 7200rpm: 39000kbytes/sec.
SuperMicro 6013P-8 SCSI 320 72Gb SCSI 10000rpm: 65000kbytes/sec.

The IDE drives are on seperate busses.  The SCSI drives are on the same bus.

I think that the 320Mhz SCSI busses are a bit faster than the 133Mhz ATA
busses.


>     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)
>
>     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.
>
>     In short if you have money to burn then by all means get SCSI but
> most people are better of spending

I suppose that's your choice.  Another way of looking that things is to
consider the worth the server has to your business and factor that into
how much you should consider spending on equipment.

e.g. if the server can be attributed to £10,000/year, then perhaps a
cheap PC will do.  If £1 million of your business relies on the server,
then perhaps you should look into investing more into it.


Regards,


Nick.


--
Nick Burrett
Network Engineer, Designer Servers Ltd.   http://www.dsvr.co.uk