Implement Cyrus IMAPD in High Load Enviromment

Vincent Fox vbfox at
Mon Sep 28 11:59:43 EDT 2009

Lucas Zinato Carraro wrote:
> - Exist a recommended size to a Backend server ( Ex: 1 Tb )?
Hardware-wise your setup is probably overkill.
Nothing wrong with that.

Sizing of filesystems IMO should be based on your
tolerance for long fsck during a disaster.  I run ZFS which
has none of that and don't want to ever see it again on
a mail-spool.  Linux journals IME reduce the probability of it
but you will still find yourself looking at fsck prompt and
having to decide:

Y = hours of downtime while I make sure it's actuallly OK
N = get it going, cross fingers.

Most Linux admins don't turn on full data journalling anyhow
quoting "performance reasons" they leave the default which is
journalling metadata.  So you don't really know how your data
is doing until it goes kablooey and you do an fsck with the
filesystem unmounted.   I wouldn't go over 500 megs per FS
until Linux has production BTRFS or something similar.

In ZFS the backups are trivial.  A script does a
snapshot at 23:55 takes a few seconds to complete, then
the backup is made of the most recent snapshot.  We keep
14 days of snapshots in the pool almost all recovery operations
are satisfied from that without hitting tape.  The overhead of
our snapshots increases storage about 50% but we are
still FAR below max usage at only about 20% filled pools with
LZJB compression in the meta dirs and gzip on the messages.

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