> > > A note about SCSI vs IDE... I have recently tried both on a dual
> P3 with
> > > 1gb of ram running Mandrake 7.2. I was amazed the idle CPU's were
> > > running near 20-23% with nothing other then a bash shell running
> on 2
> > > IBM IDE ATA 100 drives. I converted to 2 IBM SCSI U2 drives and
> the idle
> > > CPU's went down to 0-2%. This was a tremendous difference. I feel
> SCSI
> > > is a must.
>
> I have a suspicion that you didn't try using hdparm first to tune up
> your disks. Have you set them up with 32-bit transfers, UDMA, and
> unmasked interrupts? I am running a single 40 GB Maxtor 5400 UDMA/66
> disk, and even when I am stress testing the database, about 96% on
> each CPU goes to user-space postmaster processes. The system CPU
> consumption rarely goes above 4%. And FYI, I am running a dual 1 GHz
> P3 on a VP6. The IDE disk is connected to thepromise controller. I
> haven't tried it on the VIA, but I suspect the results would be the
> same. The only way I can see your CPU consumption going to 20% is if
> you are using PIO, and haven't tuned up your disks.
I will ditto that. IDE is terrible _unless_ you are using DMA for data
transfer. Without DMA, the CPU is involved in transfering all data
to/from the drive, hence your 20% CPU utiliation and terrible
performance.
--
Bruce Momjian | http://candle.pha.pa.us
pgman@candle.pha.pa.us | (610) 853-3000
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