> 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. Let me clarify: Iozone does a nonsequential series of sequential tests, specifically for the purpose of identifying the performance tiers, separating the various levels of hardware accelerated performance from the raw disk performance. This is the reason why I took out all but 4G of the system RAM. In the (incomplete) results I have so far, it's easy to see these tiers for a single disk: . For filesizes 0 to 4M, a single disk writes 2.8 Gbit/sec and reads ~40-60 Gbit/sec. This boost comes from writing to PERC cache, and reading from CPU L2 cache. . For filesizes 4M to 128M, a single disk writes 2.8 Gbit/sec and reads 24 Gbit/sec. This boost comes from writing to PERC cache, and reading from system memory. . For filesizes 128M to 4G, a single disk writes 1.2 Gbit/sec and reads 24 Gbit/sec. This boost comes from reading system memory. . For filesizes 4G to 16G, a single disk writes 1.2 Gbit/sec and reads 1.2 Gbit/sec This is the raw disk performance. (SAS, 15krpm, 146G disks) > Please add some raidz3 tests :-) We have little data on how raidz3 > performs. Does this require a specific version of OS? I'm on Solaris 10 10/09, and "man zpool" doesn't seem to say anything about raidz3 ... I haven't tried using it ... does it exist? > 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 :-) I'm guessing iosnoop is an opensolaris thing? Is there an equivalent for solaris? I'll post both the raw results, and my simplified conclusions. Most people would not want the raw data. Most people just want to know "What's the performance hit I take by using raidz2 instead of raidz?" and so on. Or ... "What's faster, raidz, or hardware raid-5?"
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