Thx to Dr. Tom Blinn, here is his explanation.
Mehmet Mirat Satoglu
---------- Forwarded message ----------
Date: Sun, 06 Feb 2000 12:01:27 -0500
From: "Dr. Tom Blinn, 603-884-0646" <tpb_at_doctor.zk3.dec.com>
To: Mirat Satoglu <mirat_at_bornova.ege.edu.tr>
Subject: Re: primary defects ?
> Hi,
>
> My alpha's scsi disk is a noisy one. So i wanted to check if it is ok
> or not. scu gives 503 primary defects and 0 grown defects. What does it
> mean ? Can I use it , or must i replace it immediately.
> Thx.
>
> Mehmet Mirat Satoglu
You apparently are not very familiar with disk technology. Modern disks
are expected to have some amount of "errors" on the surfaces, and there
is a lot of redundancy built into the recording techniques to assure that
most data errors can be recovered. In addition, when errors occur during
reading or writing, the failing data block is usually relocated to some
other presumably good part of the disk, which is reserved space for this
purpose. During the manufacturing process, the disk is scanned for errors
and a list is built and saved in the disk itself, and is used during any
subsequent format operation to assure that these known bad spots are not
used for data. This is the "primary defect list". It's perfectly normal
to have hundreds of entries in the list on a large disk (that is, a disk
with a large number of 512 byte blocks). The "grown defects list" is the
places that were found to be bad once the disk was in use, for which the
data was moved elsewhere. Since that list has no entries, your disk is
probably just fine. The fact that a disk is "noisy" doesn't mean that it
has any problems, unless it's bearing noise, in which case the disk will
probably fail catastrophically to the point where you would be unable to
access it with "scu". If you have an RZ26L disk, they were all noisy; I
believe there is a firmware update that might quiet them a bit. Since you
didn't say WHAT KIND of disk you've got, no one reading your message can
tell you whether the disk you've got is one that's known to be noisy in
normal operation.
If you are concerned about the reliability of the disk, then make sure
you keep good backups, or do go ahead and replace it, but be advised that
a new disk will not necessarily be more reliable than an old one that is
working OK -- new disks sometimes suffer "infant mortality", if I were
about to replace a disk with a new one, I'd want to exercise the new one
for a week or more before putting it into service with a utility such as
the "/usr/field/diskx" program or some part of the Qvet test suite that
is delivered on the console firmware update media.
Tom
Dr. Thomas P. Blinn + UNIX Software Group + Compaq Computer Corporation
Received on Sun Feb 06 2000 - 19:11:30 NZDT