On 08/30/2014 02:37 PM, Patrick Goetz wrote:
On 8/30/2014 10:10 AM, Simon Matter wrote:
I suggest -aH to preserve single instance storage in the backup.
Does cyrus use a lot of hard links? I use rsync a lot to create
snapshot backups, and use hard links across snapshots to preserve space;
however, for a single instance backup and unless the filesystem includes
hard links (not normal), then the -H won't do much for you.
Cyrus uses hard links among copies of the same message in different
mailboxes, when "singleinstancestore: 1" is set, which is the default.
From the man page imapd.conf(5):
If enabled, imapd, lmtpd and nntpd attempt to only write one copy of
a message per partition and create hard links, resulting in a
potentially large disk savings.
Of course one should always use -a.
The biggest concern I have about backing up mail spools is keeping the
index and message stores in sync while the backup is taking place. A
long time ago someone suggested using cyrdump, but when I looked into
this, I couldn't find any documentation whatsoever. Is cyrdump a real
thing, or did I imagine all this?
Are you thinking of ctl_mboxlist? It allows one to dump the mailboxes
database to a flat file. In an out-of-the-box Cyrus installation the
indexes are stored with the messages in the mailbox hierarchy. If you
decide to store meta-data separately, you should simply snapshot that at
the same time you snapshot your mailstore. At the beginning of this
thread, Marcus Schopen wrote this example:
ctl_cyrusdb -c
ctl_mboxlist -d > mailboxes.db.dump
stop cyrus
lvm snaps
start cyrus
rsync/var/lib/cyrus/ and /var/spool/cyrus to backup host
remove snaps
One could simply include any meta-data volumes in the snapshotting process.
Cheers,
-nic
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