Cydrome Leader wrote:
> In comp.sys.sun.admin Richard B. Gilbert <rgilbert88@comcast.net> wrote:
>
>>Cydrome Leader wrote:
>>
>>>In comp.sys.sun.admin Jorgen Moquist <jorgen.moquist@n.o.s.p.a.m.mailbox.swipnet.se> wrote:
>>>
>>>
>>>>Cydrome Leader wrote:
>>>>
>>>>
>>>>>In comp.sys.sun.hardware Jorgen Moquist <jorgen.moquist@n.o.s.p.a.m.mailbox.swipnet.se> wrote:
>>>>>
>>>>>
>>>>>>Daniel Rock wrote:
>>>>>>
>>>>>>
>>>>>>>In comp.sys.sun.admin Cydrome Leader <presence@mungepanix.com> wrote:
>>>>>>>
>>>>>>>
>>>>>>>>just throw the drive out or RMA it.
>>>>>>>
>>>>>>>Why should I pay for it?
>>>>>>>
>>>>>>
>>>>>>Rock on Daniel, I think you know more about disks than the others know
>>>>>>about cars :-)
>>>>>>/Jorgen
>>>>>
>>>>>yup, it's always best to use broken parts, and when things do fail, to do
>>>>>nothing. Problems with machines only get better with time, they're self
>>>>>healing.
>>>>
>>>>scsi and fcal disks are "selfhealing", lots of spare tracks/cyls.
>>>>replacement and cacheing tables, one spare sector per cyl and two spare
>>>>cyls per surface as i recall.
>>>
>>>
>>>None of this keeps errors from happening in the first place. Spare sectors
>>>don't make unrecoverable read errors not happen. It's also pretty known
>>>that once you start to see errors (and that means the drive has warning
>>>you because there's something wrong), things only go downhill from there.
>>>
>>
>>Disk drives can and do survive a block becoming unreadable. SCSI drives
>>can "revector" a bad block. In some operating systems, the disk driver
>>works in conjunction with the disk to copy data from a questionable
>>block to a replacement block. This looks, to the user, like "self
>>healing". If a bad block is revectored, it's not an indication of a
>>serious problem.
>>
>>What IS an indication of a serious problem is A PATTERN of bad blocks
>>being revectored. When you see that, it's time to replace the the disk.
>>Do it NOW! Tomorrow may be too late.
>>
>
>
> and it generally always is a patter of failing blocks, not one random one
> and then things are great again for years.
>
>

I think "always" is an overstatement. I've seen a lot of disks over the
years. Some of them showed the pattern of failure I've described. Some
of them revectored a bad block or two and ran for several more years.

If a disk has critical data and is not a member of a RAID set you may be
justified in replacing it the first time it detects a bad block. In
most cases I would not get excited about a single bad block.

It also makes a difference if you have a service contract or are doing
"self maintenance".

In comp.sys.sun.admin Richard B. Gilbert <rgilbert88@comcast.net> wrote:
> If a disk has critical data and is not a member of a RAID set you may be
> justified in replacing it the first time it detects a bad block. In
> most cases I would not get excited about a single bad block.

If there is a power failure while the disk is in the middle of a write you
will most likely have a bad block. I don't worry if the number of entries
in the grown defect list keeps constant (five or less). I get suspicous
if the grown defect list grows silently.

Then I run a read analysis (or write analysis if possible) of the disk.
If the defect list has grown again, it is time to replace the disk.

But Sun doesn't care about the grown defect list, if you want to replace
a disk under service contract. "Hopefully" a read analysis of the disk
find an unrevorable read error. When enough SCSI errors have filled up
/var/adm/messages you can finally convince Sun to replace the disk.

--
Daniel

Richard B. Gilbert wrote:
> Cydrome Leader wrote:
>> In comp.sys.sun.admin Richard B. Gilbert <rgilbert88@comcast.net> wrote:
>>
>>> Cydrome Leader wrote:
>>>
>>>> In comp.sys.sun.admin Jorgen Moquist
>>>> <jorgen.moquist@n.o.s.p.a.m.mailbox.swipnet.se> wrote:
>>>>
>>>>
>>>>> Cydrome Leader wrote:
>>>>>
>>>>>
>>>>>> In comp.sys.sun.hardware Jorgen Moquist
>>>>>> <jorgen.moquist@n.o.s.p.a.m.mailbox.swipnet.se> wrote:
>>>>>>
>>>>>>
>>>>>>> Daniel Rock wrote:
>>>>>>>
>>>>>>>
>>>>>>>> In comp.sys.sun.admin Cydrome Leader <presence@mungepanix.com>
>>>>>>>> wrote:
>>>>>>>>
>>>>>>>>
>>>>>>>>> just throw the drive out or RMA it.
>>>>>>>>
>>>>>>>> Why should I pay for it?
>>>>>>>>
>>>>>>>
>>>>>>> Rock on Daniel, I think you know more about disks than the others
>>>>>>> know about cars :-)
>>>>>>> /Jorgen
>>>>>>
>>>>>> yup, it's always best to use broken parts, and when things do
>>>>>> fail, to do nothing. Problems with machines only get better with
>>>>>> time, they're self healing.
>>>>>
>>>>> scsi and fcal disks are "selfhealing", lots of spare tracks/cyls.
>>>>> replacement and cacheing tables, one spare sector per cyl and two
>>>>> spare
>>>>> cyls per surface as i recall.
>>>>
>>>>
>>>> None of this keeps errors from happening in the first place. Spare
>>>> sectors don't make unrecoverable read errors not happen. It's also
>>>> pretty known that once you start to see errors (and that means the
>>>> drive has warning you because there's something wrong), things only
>>>> go downhill from there.
>>>>
>>>
>>> Disk drives can and do survive a block becoming unreadable. SCSI
>>> drives can "revector" a bad block. In some operating systems, the
>>> disk driver works in conjunction with the disk to copy data from a
>>> questionable block to a replacement block. This looks, to the user,
>>> like "self healing". If a bad block is revectored, it's not an
>>> indication of a serious problem.
>>>
>>> What IS an indication of a serious problem is A PATTERN of bad blocks
>>> being revectored. When you see that, it's time to replace the the disk.
>>> Do it NOW! Tomorrow may be too late.
>>>
>>
>>
>> and it generally always is a patter of failing blocks, not one random
>> one and then things are great again for years.
>>
>>
>
> I think "always" is an overstatement. I've seen a lot of disks over the
> years. Some of them showed the pattern of failure I've described. Some
> of them revectored a bad block or two and ran for several more years.
>
> If a disk has critical data and is not a member of a RAID set you may be
> justified in replacing it the first time it detects a bad block. In
> most cases I would not get excited about a single bad block.
>
> It also makes a difference if you have a service contract or are doing
> "self maintenance".
>


It would be useful if you cut out irrelevant stuff when quoting - there
is rarely much point in quoting this amount, most of which is totally
irrelevant.

Dave