Date: Thu, 28 Apr 2005 10:47:32 -0500 From: Eric Anderson <anderson@centtech.com> To: Steven Hartland <killing@multiplay.co.uk> Cc: freebsd-performance@freebsd.org Subject: Re: Very low disk performance Highpoint 1820a Message-ID: <42710594.2010308@centtech.com> In-Reply-To: <06d301c54c02$98ab5ce0$7f06000a@int.mediasurface.com> References: <069901c54bfd$2967ba40$7f06000a@int.mediasurface.com> <4270F648.5030501@centtech.com> <06d301c54c02$98ab5ce0$7f06000a@int.mediasurface.com>
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Steven Hartland wrote: > ----- Original Message ----- From: "Eric Anderson" <anderson@centtech.com> > >>> Where do I start looking? > > >> First, understand that RAID 5 is dependant on fast hardware to >> performa the XOR operations. A single disk without any RAID can >> easily outperform a RAID array if the RAID array is on a 'slow' >> controller. The Highpoint controllers are not exactly high-end fast >> RAID controllers, so ~50MB/s isn't too bad for that I would say. Did >> you happen to try a vinum RAID5? How about a stripe? > > > The quoted benchmarks for this controller are ~500MB/s with 8 raptor > disks. Its a hardware RAID 5 with 8 SATA channels on 64Bit PCI-X > @ 133Mhz so under the current setup it should be achieving ~250MB/s > Im only getting 50MB/s which is just silly. > > It was also my inderstanding that the XOR is only done on write > not read. Correct - I misread the dd line. When you are doing the dd, what is your system busy doing? (top/ps info) >> You could make two RAID 5's with the controller, and then stripe those >> in vinum. You could also do a combo of two stripes in the controller, >> and a vinum mirror in FreeBSD - that would give you decent performance. > > > I could but it seems there is something more problematic a foot > here and would like to investigate the reason for the poor performance > not workaround it. What do you suspect? Some info from one of my arrays: # dd if=/dev/zero of=./testfile bs=64k count=10000 10000+0 records in 10000+0 records out 655360000 bytes transferred in 3.581413 secs (182989226 bytes/sec) (unmount / mount filesystem) # dd if=./testfile of=/dev/null bs=64k count=10000 10000+0 records in 10000+0 records out 655360000 bytes transferred in 6.747707 secs (97123362 bytes/sec) # dd if=/dev/da0s1d of=/dev/null bs=64k count=10000 10000+0 records in 10000+0 records out 655360000 bytes transferred in 11.252226 secs (58242699 bytes/sec) Seems like the reads should be faster than the writes.. Eric -- ------------------------------------------------------------------------ Eric Anderson Sr. Systems Administrator Centaur Technology A lost ounce of gold may be found, a lost moment of time never. ------------------------------------------------------------------------
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