Re: IO rate for U320 SCSI 15K RPM Hard Drive

Hi Frits,

On 10/13/06, Frits Hoogland <frits.hoogland_at_gmail.com> wrote:
>
> Biggest problem here is that it this is (very correctly stated): sequential
> IO.
> Can you guarantee you use the disks in a strict sequential way?

No I can not. In my post I have stated that "most IO operations done by oracle are random in nature"

If your IO pattern is not sequential but random (as probably most disks are
> used), the IO throughput figure drops significantly.

I agree

The 75% full thing is discussed by James Morle the last database forum. The
> 75% figure and potential performance drops have to do with read speed which
> is higher on the outer edge of a disk because of higher sector density (and
> lower seek time of the read/write head because movement is reduced).

I agree

Apparently disk manufracturers take this in account and have optimised disks
> for this now. If you want to optimise this way, check if you got any
> benefit from it.

Thanks for the info. Do you have any link where disk manufacturers has published this?

frits

Thanks,
goran

On 10/12/06, goran bogdanovic <goran00_at_gmail.com> wrote:
> >
> > Hi Lale,
> >
> > To calculate the sequential IO you can use the follwing:
> >
> > seconds per IO=(transfer time) + (track-to-track seek time) + (avg.
> > rotational latency)
> >
> > (assuming that we have track-to-track seek time between each IO)
> >
> > IOPS=1/(seconds per IO)
> >
> > for random IO you can calculate
> >
> > seconds per IO= (transfer time) + (random seek time) + (avg. rotational
> > latency)
> >
> > (assming we have random seek between each IO)
> >
> > IOPS=1/(seconds per IO)
> >
> > The transfer time, track-to-track seek time, avg. rotational latency,
> > random seek time you can find in HDD spec.
> >
> > For random seek time we can assume that we have mixture of reads and
> > writes and take the avg. of disc spec. "avg. seek time, read" and "avg. seek
> > time, write".
> >
> > Since most IO operations done by oracle are random in nature, you should
> > try sizing your system not to the calculated max. random access performance
> > but to operate at around 75% of max. performance. The reason for this is
> > that the IO response time increases as you reach the max. capacity of the
> > disk drive and the queue length can increase greatly.
> >
> > Also, take into consideration that in addition to disk drive latencies,
> > the latencies of IO controller have to be taken into the account too.
> >
> > HTH.
> >
> > goran
> >
> > On 9/28/06, Michael Erwin <michael.erwin_at_hotsos.com> wrote:
> > >
> > > Hi Lale,
> > >
> > > One would expect to find it here:
> > >
> > > http://h10010.www1.hp.com/wwpc/me/en/sm/WF06c/A1-1769079-1769113-1769113-1769139-1769139-16169139.html
> > >
> > >
> > > Nothing really available on their site...
> > >
> > > However, estimate IOPS is relatively easy with
> > >
> > > Spindle IOPS = ((RPM/60)/3)*2
> > >
> > > Or at least ~167 8k IOPS per spindle
> > >
> > > To figure out User Data Transfer rates, use the following:
> > >
> > > UDT=(Spindle Speed / 60 * Sectors Per Track * Bits per Sector * 8) /
> > > 1,000,000
> > >
> > > Bits Per Sector as defined by HP can be here:
> > >
> > > http://h18000.www1.hp.com/products/quickspecs/11531_div/11531_div.HTML
> > >
> > >
> > > So BPS=512
> > >
> > > The other two number we need is the platters used in this 146GB drive
> > > and the physical platter size (3.5", 2.5", 1", and I would assume 3.5")
> > > to determine an areal density or at least GB/Platter density to determine
> > > the inner & outer range of UDT. It will be a wide range considering Zone Bit
> > > Recording (ZBR)
> > >
> > > BTW, the whole U320 MB/Sec transfer is a U320 SCSI transfer rate and
> > > not the user data transfer rate for the drive itself.
> > >
> > >
> > > *Michael Erwin*
> > > Hotsos Enterprises, Ltd.
> > > http://www.hotsos.com
> > > Hotsos Symposium 2007 / March 4-8
> > > Visit www.hotsos.com<http://exchweb/bin/redir.asp?URL=http://www.hotsos.com>for curriculum and schedule details...
> > >
> > > ------------------------------
> > > *From:* oracle-l-bounce_at_freelists.org on behalf of lale obradovic
> > > *Sent:* Thu 9/28/2006 12:19 PM
> > > *To:* oracle-l
> > > *Subject:* IO rate for U320 SCSI 15K RPM Hard Drive
> > >
> > > Hi All,
> > >
> > > Does anyone have some information of expected IO rate (IOPS and/or
> > > MBPS) for U320 SCSI 15K RPM Hard Drive (HP 146GB U320 15K Universal HDD)?
> > >
> > > Thanks!
> > >
> > > Lale
> > >
> >
> >
>

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