Re: For Lenny: LVM, LVM+MD or just MD for mirroring?
On 5 Sep., 20:10, "nate" <debian-u...@aphroland.org> wrote:
> Jens wrote:
> > Generally I would like to hear any experiences with LVM2 you can
> > offer.
> > The last time I tried LVM I hosed everything, but that was eight years
> > ago, at least partly due to a user error, and with LVM1 on Debian
> > Woody with a self-compiled kernel on 2.4.2x.
>
> I would stick to MD for the RAID and LVM for the snapshot stuff.
Hi,
thanks a lot for your insights!
I was leaning towards that solution as well since I have experience
with MD already.
LVM is supposed to be able to do fast rebuilding by creating a log
when a device fails. MD (in 2.4 at least) always does a full rebuild,
has this maybe changed?
> It's been a while since I ran MD on Debian so I don't know how/if it
> handles installing the boot loader to the other disk. Red Hat at least
> did not by default and I put a workaround in my kickstart config to
> take care of that for me.
Just out of curiosity, what exactly did you do?
> I have used LVM/LVM2 quite a bit, though have never used snapshots.
> The most use I got out of LVM was using it with a multipathed SAN,
> over iSCSI and Fiber Channel. LVM allowed the system to find the
> volumes no matter what path they were presented down(and with
That was an advantage, true.
Nowadays you can mount using UUIDs or disk labels which also works
fine.
> Also with LVM I was able to restrict volume sizes pretty easily
OK, I do this with quotas mainly. I haven't yet come across a scenario
where these were not sufficient any more. (Except maybe for /tmp and /
var which have their own partitions).
> I believe with LVM and snapshots you have to set aside a
> fixed amount of space to store the deltas for them when
> configuring the volume group, though this may of changed.
This is still the case. This allows LVM to rebuild within minutes,
instead of hours (like MD).
This would be a big plus for LVM - if it worked. Plus, I could use a
MD device for the LVM log so it could be used if either disk fails.
> If using MD with LVM sounds too complicated you should consider
> a hardware RAID controller, that way you don't need to worry
> about boot loaders and 2nd disks, or rebuilding the array etc..
The problem here is the budget ... ;)
> For me, multiple simple layers are easier to work with than
> fewer more complicated layers.
True.
Thanks a lot!
-Jens
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