On 2019.01.07 05:46, Dale wrote:
Peter Humphrey wrote:
> On Sunday, 6 January 2019 22:13:31 GMT Dale wrote:
>
>> Even from my simple setup, LVM adds more benefits to managing data
and
>> drives than it does risk. The biggest thing, placing blame where
it
>> lies. Blaming LVM for a drive dying is placing the blame on
something
>> that wasn't the root of the problem. The dying drive was the
problem,
>> using LVM or not.
> He isn't doing that, though. As I read it, he recounted the tale of
recovering
> data from a failed drive, then imagined how much worse it would be
if it were
> in an LVM setup. [Reported speech and mixed-up tenses causing me a
problem
> here...]
>
> Thanks Gevisz, that was interesting. What we used to call a
cautionary tale.
>
From what I've read, that can be overcome. If you get say a SMART
message that a drive is failing, just remove that drive or remove the
whole LVM setup and use something else until a working drive setup can
be made. Once ready, then move the data, if the drive still works, to
the new drive. That is basically what I did when I swapped a smaller
drive for a larger one. I moved the data from one drive to another.
It
did it fairly quickly. Someone posted that it may even be faster to
do
it with LVM's pvmove than it is with cp or rsync. I don't know how
true
that is but from what I've read, it moves the data really
efficiently.
If the drive has a very limited time before failure, speed is
important. If the drive is completely dead, replace the drive and
hope
the backups are good. Either way, LVM or not, a failing drive is a
failing drive. The data has to be moved if the drive still works or
the
data is gone if it just up and dies. The biggest thing, watching the
SMART messages about the health of the drive. In the past when I've
had
a drive fail, I got error messages well ahead of time. On one drive,
I
removed the drive, set it aside, ordered a replacement drive,
installed
both drives and copied the data over. After I did all that, I played
with the drive until it failed a day or so later. Lucky? Most
likely.
Still, it gave me time to transfer things over.
While I get that LVM adds a layer to things, it also adds some options
as well. Those options can prove helpful if one uses them.
Just my thinking.
Dale
The only problem with all that is that SMART is far from completely
reliable. I recently had a drive fail, and the resulting fsck on the
next reboot messed up many files. (Not a Gentoo system, although I
don't think that made any difference.) After getting running again, I
did several SMART tests, including the full self-test, and it reported
ZERO errors. A few weeks later, it did the same thing, and shortly
after that, it failed totally. I had done a few more full self-tests
before final failure, and all came back clean. I'd really love to find
out there was something I did wrong in the testing, but I don't think
so. I have not yet completely given up on trying to recover stuff from
that drive, but as time goes on, there is less and less that I haven't
rebuilt or replaced by re-downloading or changing lost passwords, so
it's less and less important. (That was a different drive from the one
I messed up myself, as discussed in another recent thread here.)
Jack
