On 3.12.2011, at 22.30, Maria Arrea wrote: > We are using dovecot 2.0.16 with mdbox+zlib. We are now testing SiS (Single > Instance Storage) and I have 5 questions: > > 1º Is possible to "dedup" existing mdboxes?
You can dsync the mailbox elsewhere and then replace the original with the new copy. > 2º Are attachments compressed with zlib if mdboxes already use zlib? Currently attachments don't support zlib at all. > 3º I have plenty CPU to spare, should I use a low value of > mail_attachment_min_size , like 16KB ? It wastes disk seeks since it now has to read mail from 2 (or more) places in filesystem, so probably not a good idea. So in any case SiS most likely increases your disk IOPS usage. > 4º Can I "undo" SiS if I have problems? dsync will help the other way around too. > 5º We use bacula to save indexes & mdboxes, and we recover mailboxes using > doveadm import when a user "makes a fatal mistake" wiping all her Inbox. If > we enable SiS I am not really sure how can we safely restore a user's INBOX > if that user has SiS attachments. Hm. Yes, that is problematic.. Even if you knew what SIS files were used, there's no simple way to restore those with proper refcounts. I think what really should be done is writing a tool that can create/restore backups, possibly de-SISing the attachments..
