Bart Mortelmans via xmail wrote on 05/25/2015 02:24 PM:
Are you sure this will actually speed up XMail? Have you been able to compare,
specifically for XMail?


It will help for files xmail creates in /tmp and doesn't move
to an other drive (for example when the realtime filters get fired
during mail acceptance, the passed file always lies in /tmp).
Since a /tmp on a ramdisk is ultra-fast I concluded that this
will speed things up. But I'm not sure yet if xmail moves that
file to main disk.

As far as I understand how XMail processes e-mails, it actually only creates a
file one time and then moves that file around between temp-folder, spool
folder and local POP3 folders. Moving a file on the same filesystem means the
file isn't re-rewritten. If you move a file between different filesystems, it
does need to be re-written. That could actually mean that having the temp
folder on a RAM-disk might slow things down if there would be an event in
which XMail moves a file from spool to temp to local POP3 folder. When they
are all on the same filesystem, this would mean the file would need to be
written only once (and then moved around). If the temp folder is on a
different file-system, this would cause the file to be writting to the hard
drive twice and to the RAM-drive once.

Hmm. yes, true.
But there are use cases where ramdisk will be w/o question useful,
for example starting the filter-programs from ramdisk.

All mails will not only pass through the temp-folder, but will also end up in
the spool-folder. If most mails only pass through the server (and don't need
to be stored locally) then you might be able to see a speed improvement by
also placing the spool folder on a ramdisk. But this would mean that all mails
pending delivery are lost at server restart (so this isn't really recommended).

Yes, true, putting spool on ramdisk is not that a good idea :-)

cu
Uenal


Sincerely,
Bart Mortelmans


U.Mutlu via xmail schreef op 25/05/15 om 01:09:
Tip: Speeding up xmail by pointing envvar XMAIL_TEMP to a ramdisk
(here on Linux using a 64 MB ramdisk mounted to /mnt/ramdisk )

mkdir -p /mnt/ramdisk

in /etc/fstab:
tmpfs  /mnt/ramdisk  tmpfs  nodev,size=64M  0  0

then either reboot or use this cmd:
mount /mnt/ramdisk

in xmail start script:
export XMAIL_ROOT=/var/MailRoot
export XMAIL_TEMP=/mnt/ramdisk
export
PATH=$XMAIL_ROOT/bin:/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin

...

and restart xmail.

The ramdisk size should be bigger than "MaxMessageSize" (unit KB) in
server.tab.

This will speed up mail processing (at least incoming mails) significantly.
Here's more info about speed gains:
http://www.jamescoyle.net/knowledge/951-the-difference-between-a-tmpfs-and-ramfs-ram-disk

"The major benefit to memory based file systems is that they are very fast –
10s of times faster than modern SSDs. Read and write performance is
massively increased for all workload types."

One can even copy the mostly called programs (for example filters) onto the
ramdisk, but then one must use such a PATH line (instead of the above one):
export 
PATH=/mnt/ramdisk:$XMAIL_ROOT/bin:/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin



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