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Due to periodically running out of space on EBS volumes on AWS EC2, and looking to make the setup more fault resistant in case of server/volume failure, I'm considering moving a Dovecot maildir installation over to S3QL.

  1. Would there be any problem(s) with such a setup? If so, what would they be?
  2. I notice at https://code.google.com/p/s3ql/wiki/other_s3_filesystems that it doesn't support multiple mounts from different computers. The other filesystems that, according to the table, do support multiple mounts, don't seem to be in existence/maintained any more. Are there any suitable alternatives that do support being mounted from multiple servers at the same time? If the filesystem supported this, would Dovecot essentially support the simultaneous access to the same maildirs from multiple servers?
  3. Are there any other, better, ways of handling the issue of maildir space & reliability?

Thanks.

Michal Charemza
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3 Answers3

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Answer #1

I think the problems encountered with Maildir depend on how the storage is shared. You should try to set it up in a way, that all of a single users connections are accessing her mails via a single "backend" dovecot during a single session. For this you can use e.g. director

For a picture of a fairly complex example setup (with replication that you might not need) using frontend directors, see http://www.dovecot.org/img/dsync-director-replication.png It is related to the blog article http://blog.dovecot.org/2012/02/dovecot-clustering-with-dsync-based.html

Answer #2

Another possibility for S3 storage is the commercial object storage plugin from Dovecot Inc http://www.dovecot.fi/products/

thuovila
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  • Good to know about the commercial storage plugin. We're quite willing to pay. However, the cost appears to be per mailbox. Although I'm not sure how much it will be per mailbox, it's unlikely that we'll want to go down the route where there is a cost per, potentially not very much used, mailbox. – Michal Charemza Dec 04 '13 at 11:18
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To partially answer part 2 myself:

Apparently ObjectiveFS https://objectivefs.com/ supports multiple mounts (according a support email they're replied to), although I've not tested it, and can see very little information about it around on sites in general

From http://www.dovecot.org/ that Dovecot Maildir does support being accessed from multiple systems at the same time, although there might be some config regarding caching, and it doesn't mention S3QL.

Other answers of course still welcome.

Michal Charemza
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There should be no technical problems with using S3QL to store Dovecot maildirs, however, things will be significantly slower than with a local filesystem (like ext4 or btrfs). This may or may not be a showstopper for your use-case.

Nikratio
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