On 2/14/06, Adam McDougall mcdouga9@egr.msu.edu wrote:
Does anyone have any tips for tuning a netapp (and/or clients) for nfs access to Maildir email folders? I know people do it, and potentially the load on the server(s) could be less than mbox because you arent shovelling around huge files, but it seems like the netapp is a little slow with opening a larger number of files for reading one by one. By large I mean over a few thousand (three to 130 thousand I have tested with) and slow I mean between 200 and 500 headers read per second from nfs. It is only slow if the filer does not have it cached already, because followup folder opens get several thousand headers per second throughput, similar to mbox. I have not tried other nfs servers, but I have attempted to simulate the load from courier-imapd or dovecot using a shell script to read 2 dozen lines from each of several thousand mail files, and the delay seems to be the netapp. Additionally, if if is a fresh folder open (not cached anywhere), the first 2,000 or so message headers load quickly, it slows down to between 200-500/sec for the next few thousand, and if you let it get above several tens of thousands, it continues to slow even more, down to less than 100 headers per second.
I am somewhat dissapointed that the NOW forums and documentation is pretty much devoid of any mention of Maildir, let alone tuning for it.
I have a FAS940, not heavily loaded, and the clients for this are a small cluster of Dell Poweredge 2650 dual 2ghz xeons, running in pre-production environments of either Debian Linux or FreeBSD 6.x. The filer is running 7.0.3, and the files are stored in a flexvol in an aggregate spanning 3 DS14's full of disks (28x36, 14x72).
In my old life, I had an F760 and 36K mailboxes and 7M files on the filesystem.
In my current life, I have 15K mailboxes and 3.2M files on the filesystem.
I find the NetApp boxes to be more than adequate for handling of Maildir formatted mailboxes using Postfix as the MTA, either virtual or maildrop as final delivery agent, and Courier-IMAP as the end user access to the filesystems.
No special tuning except for turning off atime updates on the volume used for the Maildir storage.
For the client server side, I have used both Solaris and FreeBSD with Solaris winning in performance over NFS vs FreeBSD. I have tested both TCP and UDP mounts, and NFS v2 and V3, and I find that for both of the OSes I have used in production, UDP and NVS v2 was the highest performing.
Best of luck to you.
-- Mike Horwath drechsau@gmail.com