[EMAIL PROTECTED] said: > Here are some performance numbers. Note that, when the application server > used a ZFS file system to save its data, the transaction took TWICE as long. > For some reason, though, iostat is showing 5x as much disk writing (to the > physical disks) on the ZFS partition. Can anyone see a problem here?
I'm not familiar with the application in use here, but your iostat numbers remind me of something I saw during "small overwrite" tests on ZFS. Even though the test was doing only writing, because it was writing over only a small part of existing blocks, ZFS had to read (the unchanged part of) each old block in before writing out the changed block to a new location (COW). This is a case where you want to set the ZFS recordsize to match your application's typical write size, in order to avoid the read overhead inherent in partial-block updates. UFS by default has a smaller max blocksize than ZFS' default 128k, so in addition to the ZIL/fsync issue UFS will also suffer less overhead from such partial-block updates. Again, this may not be what's going on, but it's worth checking if you haven't already done so. Regards, Marion _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
