Date: Mon, 15 Feb 1999 13:08:22 -0800 From: "Bryn Wm. Moslow" <bryn@spacemonster.org> To: freebsd-isp@FreeBSD.ORG Subject: DPT 3334UW RAID-5 Slowness / Weird FS problems Message-ID: <36C88CC6.E1621F6F@spacemonster.org>
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I recently installed a DPT 3334UW with 64MB cache in a mail server running RAID-5 with a 32K stripe on an external case on which the user mail spool is mounted. The array is comprised of 6 Seagate Ultra Wide 4.5GB SCA drives. The system is a P2 300 with 384MB and uses an additional Seagate UW drive for boot, /usr, /var, swap, and staff home directories. It doesn't go into swap often but if it does it only hits about 5 to 10 MB. The system is running FreeBSD 2.2.8. My first problem was that I initially tried to do 16K per inode to speed things up a little bit (also, I didn't need the millions of inodes that came with a default newfs on 43GB =).) However when trying to mount, fsck, find, umount, or otherwise manipulate the filesystem about 1 times out of 5 the system would hang to the point that I had to use the reset switch to get it back. If I format with the default settings to newfs, everything works fine. The same hang also occurs if I try to do 16K block size. I haven't tried anything bigger as I had an extremely tight window in which to get the machine online. Does FreeBSD have a problem with non-default fs settings? Has anyone else tried this sort of thing on such a large filesystem? I ended up having to use the default settings for newfs to get the system to work, wasting millions of inodes and bringing me to my next problem: Under load the filesystem is horribly slow. I expected some of this with the RAID-5 overhead but it's actually slower than a CCD I just moved from that was using 5 regular 2GB fast SCSI-2 drives, much slower. When running ktrace on the processes (qpopper and mail.local mainly) and watching top I can see that most of the processes are waiting for disk access. I've tried enabling/disabling various DPT options in the kernel but it's all about the same. I'd really like to stick with RAID-5 so using 0 or 1 just isn't what I'm looking for. The user directories for delivery are broken out into 1st letter, 1st two letters, username (i.e.: /home/u/us/username) to speed up dir lookups already. Any suggestions on how else to speed things up? This wasn't a problem on my old CCD, however. Lastly, I tried to find another RAID controller besides DPT that was compatible with FreeBSD 2.2.x with no luck. Upgrading to 3.1 is not an option at the moment, at least until things are more stable. Is anyone using anything in a host-based adapter (PCI) that is non-DPT? The only reason I ask is that I've seen debate recently about whether there is a problem with the DPT losing interrupts or the FreeBSD serial code is "broken". Bryn To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-isp" in the body of the message
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