Re: maildir with softupdates
From: Raphaël Marmier (raphael_at_computer-rental.ch)
Date: 07/23/03
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Date: Wed, 23 Jul 2003 17:48:30 +0200 To: Bill Moran <wmoran@potentialtech.com>
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
Raphael
Le Mercredi, 23 juil 2003, à 17:38 Europe/Zurich, Bill Moran a écrit :
> Attila Nagy wrote:
>> Hello,
>> Is this statement still valid?
>> "ext3 is unsafe for maildir, and with softupdates, so is ffs."
>> http://www.irbs.net/internet/postfix/0202/0358.html
>
> Yes,
>
> 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
> considerably.
>
> 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
> http://www.potentialtech.com
>
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