[linux-lvm] What if a drive dies ?

[linux-lvm] What if a drive dies ?

[Perplexer]

Hello.

I'm sorry if I ask something that's be asked a million times before but I
prefer answers to my specific questions. I hope someone will try to help.

I have a VG with several differently sized PVs and one LV. It is working
fine but I am affraid that one day one of the drives would fail. I'd like to
know what I'll be looking at when that happens. What if one drive would
fail in that VG ? Can I remove it and 'repair' the VG/LV to run on with
one drive less (data is written in striped mode). That would mean I got
my VG/LV back on-line but the data that was on the bad disk would be
missing (a small price to pay actually). Would I need to resize the filesystem
again with some tool or anything special ?

Thanks for the answer(s).

---------
Perplexer

[linux-lvm] Re: What if a drive dies ?

[Måns Rullgård]

"Perplexer" <perplexer@thz.net> writes:

> Hello.
>
> I'm sorry if I ask something that's be asked a million times before but I
> prefer answers to my specific questions. I hope someone will try to help.
>
> I have a VG with several differently sized PVs and one LV. It is working
> fine but I am affraid that one day one of the drives would fail.

It happened to me.

> I'd like to know what I'll be looking at when that happens. What if
> one drive would fail in that VG ? Can I remove it and 'repair' the
> VG/LV to run on with one drive less

LVM2 can run readonly with some drives missing.

> (data is written in striped mode).

That lowers your odds considerably.  I wouldn't count on recovering
anything at all.

> That would mean I got my VG/LV back on-line but the data that was on
> the bad disk would be missing (a small price to pay actually). Would
> I need to resize the filesystem again with some tool or anything
> special ?

If you didn't run in striped mode you'd probably be able to recover
most of the data from the remaining disks, the exact results would
depend on the filesystem used and which part of it was lost.  However,
in striped mode you'll lose fragments all over the place.  Recovering
from that is more or less impossible.

If your data is precious, use RAID1 or RAID5 and make regular backups.

-- 
M�ns Rullg�rd
mru@kth.se

Re: [linux-lvm] Re: What if a drive dies ?

[Perplexer]

Ahh I made a major typo .... it's a linear setup, not a striped one.

You mentioned anyway that a recovery would be somewhat possible.
I'm using ext3 journaling fs on my LV. Would I be able to mount this
LV if one PV died, meaning I would see all data except the part that
was lost with that drive or would I need to do anything special to make
the LV mountable again ?

---------
Perplexer

----- Original Message ----- 
From: "M�ns Rullg�rd" <mru@kth.se>
To: <linux-lvm@sistina.com>
Sent: Tuesday, March 02, 2004 1:08 PM
Subject: [linux-lvm] Re: What if a drive dies ?


> "Perplexer" <perplexer@thz.net> writes:
>
> > Hello.
> >
> > I'm sorry if I ask something that's be asked a million times before but I
> > prefer answers to my specific questions. I hope someone will try to help.
> >
> > I have a VG with several differently sized PVs and one LV. It is working
> > fine but I am affraid that one day one of the drives would fail.
>
> It happened to me.
>
> > I'd like to know what I'll be looking at when that happens. What if
> > one drive would fail in that VG ? Can I remove it and 'repair' the
> > VG/LV to run on with one drive less
>
> LVM2 can run readonly with some drives missing.
>
> > (data is written in striped mode).
>
> That lowers your odds considerably.  I wouldn't count on recovering
> anything at all.
>
> > That would mean I got my VG/LV back on-line but the data that was on
> > the bad disk would be missing (a small price to pay actually). Would
> > I need to resize the filesystem again with some tool or anything
> > special ?
>
> If you didn't run in striped mode you'd probably be able to recover
> most of the data from the remaining disks, the exact results would
> depend on the filesystem used and which part of it was lost.  However,
> in striped mode you'll lose fragments all over the place.  Recovering
> from that is more or less impossible.
>
> If your data is precious, use RAID1 or RAID5 and make regular backups.
>
> -- 
> M�ns Rullg�rd
> mru@kth.se
>
> _______________________________________________
> linux-lvm mailing list
> linux-lvm@redhat.com
> https://www.redhat.com/mailman/listinfo/linux-lvm
> read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
>

[linux-lvm] Re: What if a drive dies ?

[Måns Rullgård]

"Perplexer" <perplexer@thz.net> writes:

> Ahh I made a major typo .... it's a linear setup, not a striped one.
>
> You mentioned anyway that a recovery would be somewhat possible.
> I'm using ext3 journaling fs on my LV.

That's what I had.

> Would I be able to mount this LV if one PV died, meaning I would see
> all data except the part that was lost with that drive or would I
> need to do anything special to make the LV mountable again ?

It will depend on which part of the filesystem is lost.  I had a 10 GB
LV with various source code packages on it and lost maybe 2 GB
somewhere in the middle of it.  Obviously, everything on the dead disk
was lost.  The rest was mostly recovered, but many of the files ended
up in lost+found.

A different 20 GB LV had some 10-15 files each 0.5-1 GB in the root,
and no subdirectories.  This LV lost a GB or two at the beginning.
All the files were gone, even those that were stored entirely on a
good disk.  The reason for this was that all the inode information for
the root directory was stored on the bad part.

I don't know how other filesystems will deal with such situations.
I'm running RAID now to be somewhat safer.  It was a good thing too,
since one of the replacement disks turned out to be bad.

-- 
M�ns Rullg�rd
mru@kth.se