System Bottlenecks

[Spicer, Kevin]

Errol Neal wrote:
> At 04:47 PM 9/2/2003 +0100, you wrote:
>> The best I/O improvement is by making sure you've got plenty of RAM
>> and putting the MailScanner work directory in tmpfs (not either of
>> the mail queues though!)
> 
> That is a bit scary for us. Unpacking messages in a memory based
> file  system could be catastrophic. *Shudders*. Too scary to even
> think about it if for example,
> MailScanner dies and leaves a bunch of mail in the tmpfs and we
> unknowingly reboot the system... for us.. instant law suit.
> Can anyone explain how this works? Does MailScanner unpack messages 1
> at a time, does it unpack all the messages bulky in this directory?

No, its absolutely safe, so long as you only do this for the _work_ directory (/var/spool/MailScanner/incoming) and NOT the _queue_ directories (mqueue and mqueue.in).  MailScanner never removes the queue files (even when it moves the files it actually just links them into the outgoing directory then unlinks them in the incoming directory IIRC).  The MailScanner incoming directory is used to unpack batches of messages to be scanned.  Should the System crash only these unpacked _copies_ of the original message will be lost, the original message will still be sitting there in mqueue.in (on a disk based filesystem) ready to be processed by MailScanner when it is restarted.



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