On Thu, 4 Sep 2003 22:58, Eric Sproul wrote: > First, scale is a consideration. Once we began to grow our customer > base, our email volume began to increase dramatically. Qmail queues > everything to disk, so the more mail you do, the more pressure you put > on your disk I/O. The server running Qmail was always blocking while it
I was under the impression that Sendmail also queues everything to disk. How does it's queue operate then? > where the mailbox is). We chose OpenLDAP. At the time (1999), Qmail > did not have LDAP support (correct me if I'm wrong). Sendmail did. > Even if Qmail did have LDAP support then, Sendmail's source was *much* > easier to dig through for the performance tuning we did. I'm not sure what the situation was like in 1999, now Qmail and LDAP support is adequate. > Today we are very happy with our Sendmail installation. Debian and > Sendmail play very happily together, and with our modular setup we > process over 4 million messages a day with over 60,000 mailboxes. Yes, > Sendmail has had several high-profile vulnerabilities, but with Debian > and apt, we were able to stay on top of it with little difficulty. I > can see how Qmail could look attractive to a smaller site with a less > complex setup, but for us, Sendmail was the way to go. You need two mail storage servers for 60,000 accounts? Recently I was running a system with over 1M accounts on 5 storage servers. The machines all had 4G of RAM which was necessary to keep the directory structure in cache. So the servers were averaging about 2M/s of disk writes and only 200K/s of reads according to iostat. Performance was OK but dropped out at times of high load. I determined that using a NVRAM device (such as a umem card) for the primary queue would allow each server to handle twice the load with only a 7% price increase per server. I am fairly confident that the same Qmail setup could handle 4M messages and 60K mail boxes per back-end server very easily with Dell PowerEdge 2650 machines in a fairly standard setup. Of course there are lots of things you can do to tune performance, such as mounting with noatime and using a patched kernel to fix the performance limiting bugs (I used a SUSE kernel for the mail servers in question). -- http://www.coker.com.au/selinux/ My NSA Security Enhanced Linux packages http://www.coker.com.au/bonnie++/ Bonnie++ hard drive benchmark http://www.coker.com.au/postal/ Postal SMTP/POP benchmark http://www.coker.com.au/~russell/ My home page -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of "unsubscribe". Trouble? Contact [EMAIL PROTECTED]
