>
> On a 3 drive stripe on a single ultra-wide controller, with ultra enabled
> I see more like 12MB/s
>
> interleaved raid0 array of 3 st34555w 7200 rpm uw scsi disks on bt-958 uw
> scsi controller tyan 1668 dual ppro 180 440fx with 128 mb of ram.
>
> Writing the 256 Megabyte file, 'iozone.tmp'...22.650000 seconds
> Reading the file...20.980000 seconds
>
> IOZONE performance measurements:
> 11851455 bytes/second for writing the file
> 12794826 bytes/second for reading the file
please, could you try with >= 512 MB/s ?
i'll try with ultra enabled, but I don't expect anything better as the
20MB/s bandwidth of the fast-wide channel is not reached by only 2 disks.
in other words, as the channel has enough bandwidth it's useless to
insist on it.
> On Sat, 20 Jun 1998, Davide Rossetti wrote:
>
> > On Fri, 19 Jun 1998, Hubert Tonneau wrote:
> <SNIP>
> > > According to me, 5Mb/s is a resonable performance for a single
> > > disk, so 10Mb per seconds for 2 disks sounds fine.
> >
> > they are four!
> >
> > > About your test report, i was surprised to see the line:
> > > Ultra SCSI: Disabled
> > > If you want top performances, you probably need Ultra SCSI bus
> > > (20 Mb/S if narrow, 40 Mb if wild)
> > > since 2 disks require twice more bandwild on the SCSI bus that
> > > a single one.
> >
> > the theory is: ok 1 disk <= 8 MB/s --> 2 disks could use a 16MB/s
> > bandwidth, well under 20 MB/s peak SCSI2-wide bandwidth.
> > I use TWO controllers, each one driving TWO disks, so I have a 4 disks
> > striping setup.
>
> I'd probably put all four disks in the stripe on the same controller and
> turn on ultra scsi since they're st34572s the should take advantage of the
> higher signaling rate.
> since you're showing slightly higer performance for a single disk then I
> was with my st34555w hawk 4xl disks you should be showing incrementaly
> more performance from your stripe as well.
why on the same controller ? 2 controllers should provide more
parallelism, shouldn't them ?
regards.
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