ellie timoney
2018-05-21 01:36:37 UTC
Hi Albert,
The main logical difference between ordinary replication and the experimental backup system in Cyrus 3.0 is that in a replicated system, the replica is a copy of the account's current state (as of the last replication). The backup system is a historical record, not just a current state (with configurable expiry period for deleted content).
The main storage difference is that the backup system is two-files-per-user, whereas replication with normal mailboxes is one-file-per-message. So the backup system has radically lower inode usage, and the gzip compression can benefit from seeing the entire user contents (depending on your users' usage patterns).
The backup system is mainly intended for organisations who keep their backups on online HDD storage, and who want to condense backups for a relatively large number of mail servers down to a relatively small number of backup servers (hence the massive inode reduction). If you plan to use tape or other offline storage for backups, just use a normal replica so you can stop cyrus during backups without causing downtime, and dump its filesystem(s) to tape.
The backup system is also experimental. Please do not use it as your sole backup mechanism.
Cheers,
ellie
Cyrus Home Page: http://www.cyrusimap.org/
List Archives/Info: http://lists.andrew.cmu.edu/pipermail/info-cyrus/
To Unsubscribe:
https://lists.andrew.
The main logical difference between ordinary replication and the experimental backup system in Cyrus 3.0 is that in a replicated system, the replica is a copy of the account's current state (as of the last replication). The backup system is a historical record, not just a current state (with configurable expiry period for deleted content).
The main storage difference is that the backup system is two-files-per-user, whereas replication with normal mailboxes is one-file-per-message. So the backup system has radically lower inode usage, and the gzip compression can benefit from seeing the entire user contents (depending on your users' usage patterns).
The backup system is mainly intended for organisations who keep their backups on online HDD storage, and who want to condense backups for a relatively large number of mail servers down to a relatively small number of backup servers (hence the massive inode reduction). If you plan to use tape or other offline storage for backups, just use a normal replica so you can stop cyrus during backups without causing downtime, and dump its filesystem(s) to tape.
The backup system is also experimental. Please do not use it as your sole backup mechanism.
Cheers,
ellie
Hi everyone,
I'm not sure I really understand what's the benefice of backup (cyrus>3.x) vs
replication ?
Is the main goal are to save disk space with compression ? Less inode (with
large file) ?
I believe the add backup feature to cyrus-imapd was/still very lots of
work. So what's the advantage of backup vs replication_over_compress_fs.
Regards
--
Albert SHIH
DIO bâtiment 15
Observatoire de Paris
Fri May 18 22:42:34 CEST 2018
----
Cyrus Home Page: http://www.cyrusimap.org/
List Archives/Info: http://lists.andrew.cmu.edu/pipermail/info-cyrus/
https://lists.andrew.cmu.edu/mailman/listinfo/info-cyrus
----I'm not sure I really understand what's the benefice of backup (cyrus>3.x) vs
replication ?
Is the main goal are to save disk space with compression ? Less inode (with
large file) ?
I believe the add backup feature to cyrus-imapd was/still very lots of
work. So what's the advantage of backup vs replication_over_compress_fs.
Regards
--
Albert SHIH
DIO bâtiment 15
Observatoire de Paris
Fri May 18 22:42:34 CEST 2018
----
Cyrus Home Page: http://www.cyrusimap.org/
List Archives/Info: http://lists.andrew.cmu.edu/pipermail/info-cyrus/
https://lists.andrew.cmu.edu/mailman/listinfo/info-cyrus
Cyrus Home Page: http://www.cyrusimap.org/
List Archives/Info: http://lists.andrew.cmu.edu/pipermail/info-cyrus/
To Unsubscribe:
https://lists.andrew.