Basically, if you want to ensure that email wont get lost, put the maildirs and mail queue on separate partitions and mount them sync. This is what I do.

If you have to speed things, try first a battery backed raid controler and enable the write cache on it. Of course, you should always use an UPS and some will say you can take the risk of enabling soft-updates anyway.

But realise that if you have only a small load on the mail server, then having the partition mounted sync wont make such a big difference. If you are under high load, when you need performance, you also need to mount sync, as the potential of loss is much greater...

just my two cents


Le Mercredi, 23 juil 2003, ŗ 17:38 Europe/Zurich, Bill Moran a ťcrit :

Attila Nagy wrote:
Is this statement still valid?
"ext3 is unsafe for maildir, and with softupdates, so is ffs."


It's also true that any form of write-caching is unsafe, so disable
the caches on your SCSI and ATA hard drives.  Simply accept the
terrible performance hit if you want super-reliability.
Also, make sure you have redundant power supplies, UPSes and a diesel
generator out back to cover power problems.

In reality, anything comes with a certain amount of risk, and that
statement is too vague to be useful.

To my knowledge, ext3 is not unsafe by nature, it is simply unsafe
by default because the default mount is async - which will generally
be corrupted in the event of hardware failure.

UFS+softupdates generally survives hardware failure without corruption,
although it has a funny habit of losing files that were saved right
before the failure.  Result being that you could lose emails.
However ... even a sync mount can become corrupt in the event of
hardware failure, although it's much less likely.

So you need to determine the risk level you're willing to accept as
well as the performance you require.  And you probably need to do more
research than accepting that one-line statement, as it's too vague to
properly describe the potential risk/benefits.

This reminds me of the days when DOS first got disk-caching via a
TSR (what was the name of that thing) and all the IT folks kept saying
"Don't use it, it's dangerous" without understanding why it was
dangerous.  I used it anyway, because it improved performance

Also, this is off-topic for -CURRENT, please remove -CURRENT from the
CCs if you respond. I'm redirecting to -QUESTIONS for future discussion.

Bill Moran
Potential Technologies

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