[Dovecot] Dovecot altmove questions

[Maria Arrea]

Hello

 We are using Dovecot 2.0.17 with mdbox+zlib and we are evaluating alternative storage. These are the relevant settings 

 mdbox_rotate_interval = 1d
 mdbox_rotate_size=60m

[...]
 zlib_save_level = 9 # 1..9
 zlib_save = gz # or bz2

 [...] zlib plugin enabled in dovecot-lda


These are my questions:

 1º General mdbox question. We are happy usings zlib_save, but we would like to try bzip2 compression. Can we change zlib to bzlib without problems? In other words, can we mix & match gzipped and bzipped messages in the same mdbox file ?

 2º With doveadm altmove we can move messages matching a pattern to alternate storage. I have read an older post in this mailing list about passing specific mdbox options to doveadm altmove. Should be a good idea to have a "main" mdbox area with zlib 9 and mdbox_rotate=1d and mdox_rotate_size=60m and an "alternate area" with bzip9, mdbox_rotate=1 week and rotate_size > 60 MB? In the alternate area should only be "old" mail (1 year older).

 3º We have separate raids for indexes (raid 1+0) and mdboxes (raid 5). We have almost 3 TB of gzipped mdboxes, and our backup (bacula) is taking almost 16 hours to make a full backup. Our main problem is that indexes are backupd hours before mdboxes, and that bring us some inconsistencies. What is the "right" way of backing up for separate indexes and mdboxes?

 Thank you for your support.

 Maria