[lug] RH Linux download + hdparm

[Sexton, George]

Which brings up a really under appreciated point. Just because the interface
is rated at a certain speed it doesn't mean the drive can do anything like
that kind of speed on sustained reads or writes.

A good example is Ultra-160 SCSI drives. Generally, the drives cannot read
or write more than 20-25MB second. Period. End of sentence. Look at the
sustained throughput rate specification if you want to find out what you can
realistically do with a drive.

I just took a peek at a MAXTOR spec and see that they don't even report this
number. I know IBM 10K Ultra-160 drives are something like 22MB/Sec. I
seriously doubt that consumer grade drives are faster than this.

So, the reality is that in a single drive configuration you are unlikely to
ever see more than 25MB Sec across the bus for sustained reads/writes.


>> for the specs on the drive, I discovered that although the drive
>> electronics has the ATA-100 interface, the rest of the components were
>> from the ATA-66 drive, with a corresponding throughput.  IOW, just
because

-----Original Message-----
From: lug-admin at lug.boulder.co.us [mailto:lug-admin at lug.boulder.co.us]On
Behalf Of John Karns
Sent: 18 October, 2001 12:33 PM
To: lug at lug.boulder.co.us
Subject: Re: [lug] RH Linux download + hdparm


On Wed, 17 Oct 2001, Calvin Dodge said:

> On Wed, Oct 17, 2001 at 06:58:00PM +0000, Greg Horne wrote:
> >
> > Do the different distros on them make any differece?  Do the hard drive
> > brands play a big role in this?  Are there any safe tweaks to speed up
> > access times?

> The drives do make a difference - Mom's 500 Mhz K6-based system (with
> a Tyan S1598 motherboard) has a 5 gig Micropolis and a 30 gig IBM.
> The Micropolis maxes out at about 4 megs/second, while the IBM (a 5400
> RPM model) does about 16-17 megs/second.

Indeed, and labels can also be misleading.  I recently bought a 40GB
Quantum ATA-100 drive.  I wasn't so much interested in the data band width
(bw) as much as the large capacity.  In perusing the Quantum Internet site
for the specs on the drive, I discovered that although the drive
electronics has the ATA-100 interface, the rest of the components were
from the ATA-66 drive, with a corresponding throughput.  IOW, just because
a drive has an ATA-100 interface doesn't guarantee that
the drive fully supports the spec.

----------------------------------------------------------------
John Karns                                        jkarns at csd.net


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