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Re: [rdiff-backup-users] Moving the backup-location to another machine

From: Ron Leach
Subject: Re: [rdiff-backup-users] Moving the backup-location to another machine
Date: Sun, 12 Jan 2014 14:01:17 +0000
User-agent: Mozilla/5.0 (Windows; U; Windows NT 6.0; en-GB; rv: Gecko/20110414 Lightning/1.0b2 Thunderbird/3.1.10

On 12/01/2014 12:15, Chris Wilson wrote:

total != used+available because some blocks are reserved for use by
administrators (the root user) by the filesystem.

The number of reserved blocks is:

* Old system: 1894289664 - 1874215424 - 20074240 = 0
* New system: 1922726712 - 1825057796 - 4 = 97668912, or 5% of total

It seems that someone reduced the number of reserved blocks on your
old system to zero.

That was set by the Debian installer, in fact, but it was xfs, though, not ext4. This new lv is ext4.

It's an extremely bad idea in my view to run an ext4 filesystem over
80% full, as it results in increasing fragmentation over time and
there is no defragmentation tool available.

Very interesting point. We keep the backup increments indefinitely so, other than rdiff-backup housekeeping files, the bulk of the filesystem stays in existence. No deletion, in practice. I'm not sure if the reverse-diffs change on each backup run, or whether additional new reverse diffs are created each time any source files (our main, and user, files etc) for the backup alter.

I'm going to check whether xfs does things differently - I am very anxious to move this archive. The lv only exists for backup destination and, since our existing backup failed to copy onto the lv, I can start again and put a different filesystem on it.

Chris, that was an extremely helpful post; it has pointed me towards a more critical appraising of suitable filesystems.


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