Holger Parplies wrote at about 20:16:49 +0200 on Tuesday, July 23, 2013:
> Hi,
>
> Richard Shaw wrote on 2013-07-23 12:43:19 -0500 [Re: [BackupPC-users] Move
> BackupPC "TopDir" To New Larger Hard Drive]:
> > On Tue, Jul 23, 2013 at 11:39 AM, Holger Parplies <wbppc AT parplies DOT
> > de> wrote:
> >
> > > Hi,
> > >
> > > backuppc AT kosowsky DOT org wrote on 2013-07-23 09:01:09 -0400 [Re:
> > > [BackupPC-users] Move BackupPC "TopDir" To New Larger Hard Drive]:
> > > > Aaron Cossey wrote at about 14:13:26 +0200 on Tuesday, July 23, 2013:
> > > > > Sorry but all those pipes are going to slow the transfer
> > > > > needlessly.
> > > >
> > > > While I too use SIGINFO, I doubt the extra pv pipe will slow anything
> > > > down given that disk read/write is by FAR the rate limiting step...
> > >
> > > well, yes, but the pipes *do* mean data has to be copied around
> > > needlessly,
> > > which does come at *some* cost (possibly CPU load).
> > >
> > > My recommendation would be dd_rescue, which shows you progress, handles
> > > read
> > > errors, has a less error prone command line syntax ...
> >
> > I'm sure there are various opinions on this but I just replaced a hard disk
> > in my desktop computer which used LVM and it made things REALLY easy and I
> > didn't even have to reboot nor was the system ever unusable.
> >
> > If your old drive is not using LVM then you might want to consider it on
> > the new drive.
>
> I fully agree, but pvmove only works if you are already using LVM, and if you
> are, you're unlikely to ask this question in the first place ;-).
>
> You can migrate to LVM with 'dd' or 'dd_rescue' much in the same way you
> would
> transfer your data to a new partition (or whole disk) - your destination
> would
> simply be a LV.
>
> You can't use 'dd' or 'dd_rescue' or 'pvmove' if you want to change your FS
> type or your FS doesn't support resizing (presuming there still are FSes that
> don't ;-). If that's not the case, you probably shouldn't be copying at the
> file level (rsync, cp, tar, BackupPC_tarPCcopy ...). The notable exception is
> a *small* pool on a large disk, where a partition level copy will be slower.
> You'll have to find out for yourself what "small" means, but it will have
> something to do with "number of inodes" and "number of directory entries"
> (i.e. links to inodes). If you run into problems, your pool is not "small".
>
> > [...]
> > After that I grew the volume group to the full size (went from 500GB to 1TB
> > drive) and then resize2fs.
>
> You mean the logical volume :).
>
>
> One thing to keep in mind, though, when using pvmove: you still need to move
> a
> lot of data from one disk to another. During the time this takes, your data
> may be spread over two disks, meaning a failure of any one of the disks could
> lose all your data. This might not be relevant, because pvmove creates a
> temporary mirror. I'm not sure whether it would mirror the whole LV in any
> case or only a smaller portion (under some circumstances). If you are
> replacing a disk that is failing, dd_rescue might be the better approach. If
> you are just replacing a full disk which is otherwise ok, you are probably
> fine with pvmove.
>
> Of course, losing your source disk before the end of a copy with
> 'dd(_rescue)'
> has the same problems.
>
> Regards,
> Holger
I also have lost an entire BackupPC partition when resize2fs failed
at a critical juncture... that is part of the reason that I now run 2
parallel BackupPC systems with the primary one doing daily
incrementals/weekly fulls, and the secondary just doing weekly
fulls...
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