Some thoughts below... On Feb 13, 2010, at 6:06 AM, Edward Ned Harvey wrote:
> I have a new server, with 7 disks in it. I am performing benchmarks on it > before putting it into production, to substantiate claims I make, like > “striping mirrors is faster than raidz” and so on. Would anybody like me to > test any particular configuration? Unfortunately I don’t have any SSD, so I > can’t do any meaningful test on the ZIL etc. Unless someone in the Boston > area has a 2.5” SAS SSD they wouldn’t mind lending for a few hours. ;-) > > My hardware configuration: Dell PE 2970 with 8 cores. Normally 32G, but I > pulled it all out to get it down to 4G of ram. (Easier to benchmark disks > when the file operations aren’t all cached.) ;-) Solaris 10 10/09. PERC > 6/i controller. All disks are configured in PERC for Adaptive ReadAhead, and > Write Back, JBOD. 7 disks present, each SAS 15krpm 160G. OS is occupying 1 > disk, so I have 6 disks to play with. Put the memory back in and limit the ARC cache size instead. x86 boxes have a tendency to change the memory bus speed depending on how much memory is in the box. Similarly, you can test primarycache settings rather than just limiting ARC size. > I am currently running the following tests: > > Will test, including the time to flush(), various record sizes inside file > sizes up to 16G, sequential write and sequential read. Not doing any mixed > read/write requests. Not doing any random read/write. > iozone -Reab somefile.wks -g 17G -i 1 -i 0 IMHO, sequential tests are a waste of time. With default configs, it will be difficult to separate the "raw" performance from prefetched performance. You might try disabling prefetch as an option. With sync writes, you will run into the zfs_immediate_write_sz boundary. Perhaps someone else can comment on how often they find interesting sequential workloads which aren't backup-related. > Configurations being tested: > · Single disk > · 2-way mirror > · 3-way mirror > · 4-way mirror > · 5-way mirror > · 6-way mirror > · Two mirrors striped (or concatenated) > · Three mirrors striped (or concatenated) > · 5-disk raidz > · 6-disk raidz > · 6-disk raidz2 Please add some raidz3 tests :-) We have little data on how raidz3 performs. > > Hypothesized results: > · N-way mirrors write at the same speed of a single disk > · N-way mirrors read n-times faster than a single disk > · Two mirrors striped read and write 2x faster than a single mirror > · Three mirrors striped read and write 3x faster than a single mirror > · Raidz and raidz2: No hypothesis. Some people say they perform > comparable to many disks working together. Some people say it’s slower than > a single disk. Waiting to see the results. Please post results (with raw data would be nice ;-). If you would be so kind as to collect samples of "iosnoop -Da" I would be eternally grateful :-) -- richard _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
