On Sat, Mar 24, 2007 at 04:09:54PM +0100, Peer Heinlein wrote: > The performance on the discs are bad -- iostat shows up to 100% IO-usage.
There are two limits here. (1) Laws of physics, i.e. disk rotation. Let's say one drive is capable of 250 random accesses per second. Then with four drives you're not going to get more than 1,000 random accesses per second. You increase performance by adding more drives (or you can swap slower drives for faster ones, but the amount of performance you can gain is small and one-off) I don't think you said how many of these SATA disks you have. Disks are cheap, you can always add more and migrate accounts between them. (2) Filesystem and storage arrangement and their interaction. You are using RAID 1, which is good. (RAID 5 performs very badly with a regular filesystem on top of it - if the filesystem decides it wants to write one block, this translates into four disk operations on a RAID 5 array) However, better performance is achieved by using a filesystem which understands the underlying disc infrastructure, and coalesces writes in a way to maximise performance, possibly using a non-volatile RAM cache in this process. Here, the Netapp WAFL file system scores very heavily, especially for Maildir where inode creations and deletions happen all the time. If you don't want to pay for a low-end Netapp, then you could have a look at running your NFS servers as Opensolaris with ZFS. From what I've read about ZFS, it shares many of the design features of WAFL - and Solaris ought to make a decent NFS server too. But I've not used it at all. (3) As mentioned by someone else, if you are using *IMAP* then make sure it's not an IMAP or FAM/GAMIN problem which is burning up your disk. I never had any problems with POP3. I built courier under FreeBSD with no FAM libraries installed, so autoconf detected this and built the imap server without FAM support, but very few of our users were on IMAP. > should I give my NFS-server > 10 GByte RAM just for > caching? I don't think it will help with inode creation and deletion. (At least, it shouldn't do. You *could* mount your filesystem async, but then you can expect large data loss in the event of the plug being pulled while the system is running) Regards, Brian. ------------------------------------------------------------------------- Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys-and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV _______________________________________________ Courier-imap mailing list [email protected] Unsubscribe: https://lists.sourceforge.net/lists/listinfo/courier-imap
