Hi, If all of the four drives really hang off of one ATA-Controller, they may all be stepping on each other's feet as it is a blocking bus protocol. There's a speed discussion in the ATA article on Wikipedia:
http://en.wikipedia.org/wiki/AT_Attachment My current machine (W1100z) has 4 internal PATA drives that run off of 2 controllers and I have a peculiar mixture of RAID-Z and mirroring over different slices on those drives. Performance is ok for everyday use and a zpool scrub of approx. 266 GB seems to be in the order of 5 hours: # zfs list pelotillehue NAME USED AVAIL REFER MOUNTPOINT pelotillehue 266G 55.6G 28.5K /pelotillehue # zpool status pelotillehue pool: pelotillehue state: ONLINE scrub: scrub in progress, 3.69% done, 5h1m to go config: NAME STATE READ WRITE CKSUM pelotillehue ONLINE 0 0 0 mirror ONLINE 0 0 0 c0d1s5 ONLINE 0 0 0 c1d0s5 ONLINE 0 0 0 raidz1 ONLINE 0 0 0 c0d0s3 ONLINE 0 0 0 c0d1s3 ONLINE 0 0 0 c1d0s3 ONLINE 0 0 0 c1d1s3 ONLINE 0 0 0 raidz1 ONLINE 0 0 0 c0d1s4 ONLINE 0 0 0 c1d0s4 ONLINE 0 0 0 c1d1s4 ONLINE 0 0 0 errors: No known data errors Since this is a home server which is constrained by 100 MBit Ethernet anyway, I don't care about performance. My iTunes songs and MPEG-2 digital TV recordings/playback as well as PowerBook/iBook laptops run off of this pool sometimes at the same time with no problems. Knowing about current problems with Firewire (see also other firewire bugs in Artem's blog) and in search of a better solution, I decided to move my pool to external USB storage. USB 2.0 in practice gives you about the same performance as the network (I'm being conservative here), so the speed is acceptable for me. So in the future, I'm going to migrate to pairs of cheap external USB 2.0 disks which seem to function ok. Performance should be on par with the network, especially since mirroring and striping across multiple mirrors will tend to increase performance. The main advantage I see here is manageability: Just plug and unplug disks as needed or whenever they need to be upgraded or replace, without tinkering inside your machine and while it is still running. As for diagnosing your performance, I would start by monitoring device performance and throughput. You can do that using the DTrace toolkit quite easily, or even graphically with the Chime visual DTrace Tool: http://www.opensolaris.org/os/community/dtrace/dtracetoolkit/ http://www.opensolaris.org/os/project/dtrace-chime/ This is what iotop 10 says while my system is scrubbing the above pool: 2007 Mar 30 14:59:41, load: 0.15, disk_r: 369502 KB, disk_w: 0 KB UID PID PPID CMD DEVICE MAJ MIN D BYTES 0 0 0 sched cmdk3 102 196 R 131072 0 0 0 sched cmdk1 102 68 R 134144 0 0 0 sched cmdk2 102 132 R 134656 0 0 0 sched cmdk3 102 195 R 31796224 0 0 0 sched cmdk0 102 3 R 31860224 0 0 0 sched cmdk2 102 131 R 31921664 0 0 0 sched cmdk1 102 67 R 35162112 0 0 0 sched cmdk1 102 69 R 118307328 0 0 0 sched cmdk2 102 133 R 128397312 So, I seem to be actually getting about 350MB per 10 seconds, which is about 35 MB/s for 2 UltraATA/100 controllers and 4 disks. If you see something similar, this is probably expected. Hope this helps, Constantin Robert Thurlow wrote: > Hi folks, > > In some prior posts, I've talked about trying to get four IDE drives in > a Firewire case working. Yesterday, I bailed out due to hangs, filed > 6539587, and moved the drives inside my Opteron box, hanging off one > of these: > > http://www.newegg.com/Product/Product.asp?Item=N82E16816124001 > > Now, I know the single IDE controller is going to be a bottleneck, > but let me tell you how slow it is. Last night, after moving the > drives, I started a scrub. It's still running. At 20 hours, I > was up to 57.75%, and had 14.5 hours left. That's for a pool > that's 341Gb, so the scrub has to access 341 * 4 / 3, or 454Gb. > I make that something under 4 Megabytes per second. That's not > just slow, it's pathological. I was easily getting 10-20X from > this pool in the external case. > > Where do I get started at diagnosing this? I don't know much > about watching I/O throughput. > > For yet-another-fallback, I am thinking about using SATA-to-IDE > converters here: > > http://www.newegg.com/product/product.asp?item=N82E16812156010 > > It feels kind of nuts, but I have to think this would perform > better than what I have now. This would cost me the one SATA > drive I'm using now in a smaller pool. > > Rob T > _______________________________________________ > zfs-discuss mailing list > zfs-discuss@opensolaris.org > http://mail.opensolaris.org/mailman/listinfo/zfs-discuss -- Constantin Gonzalez Sun Microsystems GmbH, Germany Platform Technology Group, Global Systems Engineering http://www.sun.de/ Tel.: +49 89/4 60 08-25 91 http://blogs.sun.com/constantin/ Sitz d. Ges.: Sun Microsystems GmbH, Sonnenallee 1, 85551 Kirchheim-Heimstetten Amtsgericht Muenchen: HRB 161028 Geschaeftsfuehrer: Marcel Schneider, Wolfgang Engels, Dr. Roland Boemer Vorsitzender des Aufsichtsrates: Martin Haering _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
