Date: Fri, 8 Apr 2005 23:33:41 -0700 (PDT) From: Doug White <dwhite@gumbysoft.com> To: Danny Howard <dannyman@toldme.com> Cc: FreeBSD questions <freebsd-questions@freebsd.org> Subject: Re: (LONG) ATA Benchmark: 5.x Reads Slower than Writes Message-ID: <20050408230026.V67756@carver.gumbysoft.com> In-Reply-To: <4256EC7A.5060107@toldme.com> References: <4256EC7A.5060107@toldme.com>
next in thread | previous in thread | raw e-mail | index | archive | help
On Fri, 8 Apr 2005, Danny Howard wrote: > I don't have the time and hardware to do very scientific tests, but I > have been able to run a series of benchmarks using bonnie++ on some > systems I have available to me. The ATA-based gmirror performs > extremely well, compared to a few Adaptec RAIDs that we have, EXCEPT > that the sequential and random reads are MUCH SLOWER than the hardware > solution, and even *slower than the preceding write operations*. This > is counter-intuitive, especially since RAID1 implies slowed writes and > faster reads. I tried the benchmark on my workstation (single 2.5" IDE > in a laptop) and got comparable write-faster-than-read results. > The raw data can be viewed at > http://dannyman.toldme.com/scratch/benchmarks/ Could you place the 'dmesg' output for each system in this directory? The output here is marginally useful since it shows the bonnie command line. However, 100MB as the test filesize is really small unless the systems have 64MB of RAM though -- otherwise you're testing how well FreeBSD manages memory (or how much crap the systems are running when you run this test). For recent I/O tests I was doing with iozone I was using 10GB filesizes. This blows out the cache on just about everything. > Unfortunately, my hardware RAIDs are on FreeBSD 4, and gmirror is on 5. > My hardware RAIDs are on dual CPU systems, with 2G RAM, and my gmirror > is on a single hyperthreaded CPU with 512M. Yes, sorry, not especially > scientific. Maybe the changes in FreeBSD make a big difference? Maybe > RAM makes a big difference? Yes, lots. Both 4.x vs. 5.x and RAM :) > Sequential Read > laptop 2.5" ATA: avg 76/s # SLOWER than write! > gmirror ATA RAID1: avg 251/s # SLOWER than write! > Adaptec SCSI RAID1: avg 7862/s > Adaptec SCSI RAID10: avg 7618/s I'd be really careful here... that is # of files read per second after the create, and as pointed out before, SoftUpdates usually gets you a big win until it has to flush the directories out then things suffer during the actual flush op since the disk gets hammered. Lots of free memory to use for the directory cache helps. The disk cache on the RAID controller is buying you even more. From your results you were getting 9ms latency which is spot-on so I think you are simply misinterpreting your results here. File creation tests are usually more for filesystem-specific benchmarking than for throughput benchmarking. I'd suggest something more like iozone for throughput testing. If the volumes have nothing on them you care about then rawio can also be instructive. -- Doug White | FreeBSD: The Power to Serve dwhite@gumbysoft.com | www.FreeBSD.org
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20050408230026.V67756>