[Dovecot] Effects of migration
So, to follow up to my previous thread, we just successfully migrated our NFS-based mail cluster from qmail pop, courier imap, and bincimap to dovecot 1.1rc1. Overall the transition was very smooth, the only unexpected adjustment was having to implement ntpd on each box, rather than doing an hourly ntpdate against our local ntpd server, to prevent dovecot from crashing itself from too much drift. The impact has been severe! Even with NFS-stored indexes, our netapp is seeing 1/6th of the NFS ops per second, and its CPU utilization is now at 1/3rd previous levels. The only user comment thus far was thanking us for bringing IMAP folders out from under INBOX. Dovecot is truly excellent. In my book, Timo joins Wietse Venema and Marc Martinec to form the backbone of the premiere open source mail solution. For now, praise will have to suffice. I do, however, maintain a little IOU list that I intend to fulfill at some point in the future, and Timo is now high on the list. Thanks again! Andy --- Andy Dills Xecunet, Inc. www.xecu.net 301-682-9972 ---
Re: [Dovecot] Effects of migration
Words by Andy Dills [Wed, Mar 05, 2008 at 11:23:08AM -0500]: So, to follow up to my previous thread, we just successfully migrated our NFS-based mail cluster from qmail pop, courier imap, and bincimap to dovecot 1.1rc1. Overall the transition was very smooth, the only unexpected adjustment was having to implement ntpd on each box, rather than doing an hourly ntpdate against our local ntpd server, to prevent dovecot from crashing itself from too much drift. The impact has been severe! Even with NFS-stored indexes, our netapp is seeing 1/6th of the NFS ops per second, and its CPU utilization is now at 1/3rd previous levels. Yeah. We went from a solution like yours to a based on dovecot imapd and we reduced the servers in 1/3 and the server load to half. Pretty impressive :) -- Jose Celestino http://www.msversus.org/ ; http://techp.org/petition/show/1 http://www.vinc17.org/noswpat.en.html If you would have your slaves remain docile, teach them hymns. -- Ed Weathers (The Empty Box)
Re: [Dovecot] Effects of migration
On Wed, 2008-03-05 at 11:23 -0500, Andy Dills wrote: The impact has been severe! Even with NFS-stored indexes, our netapp is seeing 1/6th of the NFS ops per second, and its CPU utilization is now at 1/3rd previous levels. Have you thought about enabling Squat indexes? I'd like to know how much it would affect I/O and CPU usage in larger installations. CPU grows (maybe a lot) but searches should be faster and use very little I/O as a result. signature.asc Description: This is a digitally signed message part
Re: [Dovecot] Effects of migration
On Thu, 6 Mar 2008, Timo Sirainen wrote: On Wed, 2008-03-05 at 11:23 -0500, Andy Dills wrote: The impact has been severe! Even with NFS-stored indexes, our netapp is seeing 1/6th of the NFS ops per second, and its CPU utilization is now at 1/3rd previous levels. Have you thought about enabling Squat indexes? I'd like to know how much it would affect I/O and CPU usage in larger installations. CPU grows (maybe a lot) but searches should be faster and use very little I/O as a result. By CPU, do you mean local server (nfs client) CPU or netapp CPU (nfs server)? I'm guessing the former...for what it's worth, for those who have yet to have the pleasure of using a Netapp, the CPU utilization is basically your ultimate barometer of utilization with netapps. As long as you don't start hitting 90% CPU consistently, they will provide better throughput than local SCSI disks. The CPU tops out well before the I/O, a nice change of pace. Local CPU is of little concern typically, as mail serving (filtering is handled elsewhere) is almost purely I/O. However, I'm not sure how much value I would place on optimizing searches at this point...do users really do much of that? It seems to be potentially valuable yet underutilized. Do you have some links so I can educate myself more about squat indexes? Andy --- Andy Dills Xecunet, Inc. www.xecu.net 301-682-9972 ---
Re: [Dovecot] Effects of migration
On Wed, 2008-03-05 at 23:02 -0500, Andy Dills wrote: Have you thought about enabling Squat indexes? I'd like to know how much it would affect I/O and CPU usage in larger installations. CPU grows (maybe a lot) but searches should be faster and use very little I/O as a result. By CPU, do you mean local server (nfs client) CPU or netapp CPU (nfs server)? I'm guessing the former... Yes, former. Local CPU is of little concern typically, as mail serving (filtering is handled elsewhere) is almost purely I/O. Yes, but at least initial Squat index building is very CPU (and maybe memory) hungry. :) However, I'm not sure how much value I would place on optimizing searches at this point...do users really do much of that? It seems to be potentially valuable yet underutilized. Do you have a webmail? Thunderbird also uses server-side message body searches. Outlook/Apple mail doesn't. Anyway since Squat indexes are built only when doing body searches enabling them wouldn't hurt for the rest of the users, although it would increase disk space usage. Do you have some links so I can educate myself more about squat indexes? http://wiki.dovecot.org/Plugins/FTS has something signature.asc Description: This is a digitally signed message part
