[nzlug] LVM Corruption on RH AS4

[Michael Field]

Hi Vik,

..and if it is not a hardware problem, my vote is for software! :-)

My first off-the-cuff opinion, if the disk is out of warranty then get a
new one. Why?

- Without decent diagnostics you can't tell when the disk firmware has
declared a sector bad and mapped it out to a spare one. If it has done
this the disk will then format and work again until another sector goes
bad.

- disks do die, no matter how much you wish them not to.

- If you put a new disk in and it works you will be happy.

- Even if it proves to be something else, you have a known good 
disk to test with.

- Everybody needs a new, bigger, faster disk ;-)

- At $100 for a small disk, which you can use for backing up important
files (photos?) in case you primary fails, why not?

Oh, Western Digital and others have some low-level (windows) diagnostics
that can query the drives internal error counters.

If you really want to solve the problem properly some more info would
help, the questions and tested that jump to mind are....

- Have the tried "dd if=/dev/<disk - eg hda> of=/dev/null" and waited to
see if any read I/O errors are logged? (Boot the rescue CD if the system
is unbootable).

- It is very rare to get silent disk corruption on most systems - is
anything else unusual showing up in the 'demsg' output or
'/var/log/syslog'?

- Has the system ever been stable? Has it only been a problem since an
upgrade or install?

- Have software changes been applied? Was the system running anything
else successfully?

- If it is on "winTel server class" hardware, do the management tools
show anything? How about the integrated hardware error/event log?

- How did they discover this? Did the system spontaneously reboot giving
corrupted disks? Or did they just do a normal reboot one day and it
happened?

- Does the system have ECC memory in it? Do they have the the BIOS
memory check enabled? Could the run a memory tester?

- Is the disk's partition table geometry consistent with the disk's BIOS
settings?

- Do they have overlapping partitions in the disk's partition table?

- Is it just one disk getting corrupted, or is the corruption over a
pool of disks? 

- Are all the disks on the same IDE/SCSI controller?

- Is it just the headers that are being corrupted or the whole disk?

- Are all the system and components firmware up to date?

And finally, if you do have the time, and the disk is junk otherwise,
and you don't want any of the data off of it:
- Boot off of another Linux disk or system recovery CD. 
- Then wipe the disk with "dd if=/dev/zero of=/dev/<disk> bs=16k", 
- Verify that the disk is all zeros with "dd if=/dev/<disk> bs=16k". If
you don't see junk on the screen then you have 'scrubbed' the disk of
all data, and you can try installing again.

Oh, and it seems that cold weather brings out the worst in disks! 

Cheers

Mike

-----Original Message-----
From: nzlug-bounces at linux.net.nz [mailto:nzlug-bounces at linux.net.nz] On
Behalf Of Vik Olliver
Sent: Tuesday, 19 June 2007 10:01 a.m.
To: NZ Linux Users Group
Subject: [nzlug] LVM Corruption on RH AS4

A friend of mine is reporting LVM header corruption on RH AS4. This
doesn't seem to be a general issue, but I thought I'd pick the brains of
the assembled to see if anyone had any theories. My favourite is
hardware failure.

Vik :v)
-------8<---------8<---------8<---------8<---------8<---------8<-----
Sky-diving: Good 'til the last drop.


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