John Summerfield wrote:
Use good hardware, good software (RHEL or a clone), IMAP and not
POP3, and use one of the reliable RAID (1, 4 or 5) choices for your
mail (and other critical data) storage.
Been using POP3 forever with no problems (except some Mac problems with
You do have a problem, your mail is scattered all over the place. imap
keeps it on the server.
That's a matter of perspective. If they POP3 it off my server, it's
their problem, not mine. If I use IMAP, store it on the server, then if
one server crashes, I switch to a backup with an old rsync and people
get mail marked as new that they already read, or get multiples of the
same mail. Meanwhile, email is lost on the original system.
Dovecot). Have RAID1 software setup for years as well. Keep getting
drive failures and looking back into hardware RAID with high quality
equipment (as mentioned before).
Even if a dodgy Fedora software update doesn't get you, you still
have to contend with frequent upgrades of the software.
Yes, I've dealt with 'dodgy' updates and config files being lost by
auto updates, and bug fixes that mess things up that worked fine.
For the price, it has been acceptable (at least to the people in
charge of the purse strings).
Price a problem? CentOS is free of charge. It also costs less.
OK, Fedora is free. I'm talking about not paying licensing for Red Hat
Enterprise, Suse Enterprise etc. Your saying CentOS is far more
reliable than Fedora? They're all Linux right? Fedora is on the edge
of development, I understand that, but that seems to be a good place,
latest features, latest patches, latest security fixes. Still get
security patches and updates with CentOS right? What are you saying is
the difference?
Note that RAID _can_ include a network block device (nbd or enhanced
nbd drivers), and drbd also provided RAID1 over a network, and is
tolerant of breaks in connectivity.
note that LVM can provide hot backups.
One trick I've hard of is to define a firewire drive (presumably USB
or other hotplug drive) would do as part of a mirror pair. Backup
goes something like this:
Plug it in
Resync.
Detach (I don't recall the fine details here)
Unplug.
Used removable drive trays for rsync backups without the RAID. Now we
got backup systems that are rsync backed up and ready to run in
failures. However, any email that was delivered between the last
rsync and the failure gets lost temporarily or permanently. Hence my
idea for NFS mount to quality RAID1
NFS has its own problems. enbd and drdb are better than rsync.
NFS is not RAID or backup. I'm not sure I've explained clearly what my
idea is. <explanation below>
Google for terms such as "reliable linux" "high availability linux"
"linux cluster" etc for more details.
Google'd and Yahoo'd...seen hundreds of ideas mostly based on
heartbeat. In fact I most recently was looking into Red Hat's Global
File System and clustering:
http://www.redhat.com/gfs/
http://www.redhat.com/cluster_suite/
Trying to figure out how Red Hat is accomplishing these things with
open source, or if they are adding their own proprietary background
stuff.
Look at CentOS. If it's in that (I believe it is) then it's OSS.
All-in-all, fun discussion, but completely off topic from my original
post and still doesn't answer my question.
I'm more concerned with the underlying problem than with your proposed
solution.
What exactly do you see as the 'underlying problem'?
Do you want the best solution?
Well that's just silly to ask now isn't it?
My idea is to use NFS to mount another file server that has a quality
hardware RAID1 solution with hot swap drives ideally. Then the primary
mail application server runs a minimal drive to boot the OS and start
the email program. I NFS mount the file server for mail storage. This
way, if the primary mail server fails, a second application server
(probably shared with the web or domain server) can takeover with the
file system right where the primary mail server ended.
