Re: (reiserfs) Re: LVM / Filesystems / High availability
Florian Lohoff (flo@quit.mediaways.net)
Thu, 25 Jun 1998 11:45:43 +0200
On Wed, Jun 24, 1998 at 01:51:49PM -0400, Theodore Y. Ts'o wrote:
> Date: Wed, 24 Jun 1998 13:17:33 +0200
> From: Florian Lohoff <flo@quit.mediaways.net>
>
> There are logically no holes. If you have to take a PE out of service in
> the middle you multiple choices:
>
> 1. Shrink the filesystem by the size of one PE and exchange
> the PE in the middle by the PE got free at the end
> (Assuming Grow-/Shrinking always happens at the end, otherwise
> you *NEED* PE/LV aware FSes)
> 2. Replace the PE by another PE in the Volume Group beeing
> completely transparent to the Filesystem.
>
> OK, suppose I have a 54 terrabyte filesystem, with all PE's in use, and
> I need to remove a 9 gigabyte disk from the middle of the filesystem,
> because it's failing.
>
> I can't do (2) because I don't have a spare PE to use.
>
> I could do (1) but that would mean temporarily copying *more* data to
> the failing 9 gigabyte disk as part of the compaction process, thus
> putting that data at risk. The increase disk activity would also make
> it more likely for the disk to fail completely. Once the filesystem has
> been compacted you now have space to exchange the PE, but that involves
> needless 9 gigabyte copy on top of the overhead of the filesystem
> compaction.
This is why you should first attach a new 9GB Disk attach it
to you volume group and copy all data from the failing
to the new drive. Ok ... i see this as a problem
> There are plenty of filesystem implementation efforts which are trying
> to do this. Reiserfs, dts, lfs, among others. In my experience there
> are far more filesystem projects started than actually finish, although
> I'll be the first to acknowledge that there are some pretty sharp people
> working on some of the other filesystems. In the true Bazaar model,
> we'll see which approach results in a stable, performant and robust
> filesystem first. It should be an interesting experiment.
>
> - Ted
We will see ... i myself wont be happy to see this in the ext2
instead of splitting the complexity to different abstraction layers
to bring down complexity and increase reliability and flexibility.
Flo
--
Florian.Lohoff@mediaWays.net +49-5241-80-7085
aka flo@mini.gt.owl.de @HOME +49-5241-470566
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