[Wolves] Question 1st, Rant 2nd

[Andy Smith]

On Thu, Jun 15, 2006 at 12:07:00PM +0100, Peter Cannon wrote:
> Rant.
> 
> F$%&@ P$£@?& S%$£@ fsck, e2fsck oh yeah poxy LVM. So far I have spent 7 days 
> poncing around with three differant HDD's all reported bad sectors disk 1 was 
> a 40GB I got the data off and stuck a screw driver through it in temper disk2 
> 20GB again bad sectors, I threw that one in the bin.

If I put several disks in the same machine and they all reported
failures I'd begin to suspect my cabling/controller/motherboard,
depending on the errors seen.

> Disk3 (This one) bad sectors, can I run any checkers on it? can I bollocks, 
> the web and the forums all say "Oh just run fsck" get stuffed you lying pigs 
> that doesn't work especially with LVM.

fsck being FileSystemChecK and LVM not being a filesystem, also fsck
designed to find/fix problems with filesystems not the devices they
are on top of...

Try badblocks, SMART "long" self-tests or a simple:

dd if=/dev/sda of=/dev/null

to read from /dev/sda, or:

dd if=/dev/zero of=/dev/sda

to write to (and completely clobber anything on) /dev/sda.

If they complete fully without errors then the disk is basically
healthy.  This will work regardless of what filesystem, software
RAID, LVM or other schemes you are using, though of course the
second "dd" command will destroy any data on the device.

> I finally managed to find a post tucked away on a missleading subject that LVM 
> often says bad blocks and that fixing LVM is patchy at best.

LVM cannot itself trigger a block device failure as it is a level
above that.  Certainly using LVM can give your disks a bit more of a
workout but if block device errors happen then they are as real as
if they happen without LVM.

(which doesn't mean to say they are really real as they can be
caused by: overheated drives, poor cabling, insufficient power,
driver bugs, incomplete SATA II support, ... just to list cases I
have personally experienced that produce block device errors without
there being damage to the drives -- aren't computers fun?)

Have you got the URL to this post about LVM and bad blocks by any
chance?

Cheers,
Andy

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