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Re: LVM/btrfs - Was: Re: firefox-37, where to put



Reco wrote:
> Petter Adsen wrote:
> > > Resizing just works, as long as you don't forget the correct order for
> > > changing the filesystem and the volume. I.e.
> > > 
> > > 1) Enlarge - volume first, filesystem last.
> > > 2) Reduce - filesystem first, volume last.

I am compelled to note that resizing for increasing works great.  But
resizing for shrinking is very, very, very slow.  Shrinking isn't a
very well used path.  It works.  If you have ten days to let it
complete with out power failure.  Avoid every shrinking a file system.  If you
must shrink it is much better to backup, create new of smaller size,
restore from backup.

> > I expect the combination of ext4 and LVM is so common that ext4 would
> > be a good choice of filesystem if I ever get the need to resize?

I pretty much agreed with everything Reco said.

I set up my own machines with mdadm RAID1.  On top of that is LVM.  On
top of that is ext4.  I always use a separate /boot on mdadm RAID1
without LVM using ext2 simply to avoid the wasted space of a journal
on that file system.  I RAID1 everything including swap.  This may not
be an exciting combination but the combination works reliably.

You mention wanting to use snapshots so I must suggest spending some
time researching blog articles on lvm snapshots.  I have heard of
issues concerning race conditions in the code path leading to
corruption.  I have heard some bad things about LVM at that
intersection.  Sorry I can't recall specifics but it had to do with
continuous build systems that were exercising the path all of the time
and tripping over problems with it.  I wish I had a URL to reference.
I would be very happy if someone countered this with information
saying the opposite.

Bob

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