On Jun 24, 2010, at 5:40 AM, Robert Milkowski <mi...@task.gda.pl> wrote:
> On 23/06/2010 18:50, Adam Leventhal wrote: >>> Does it mean that for dataset used for databases and similar environments >>> where basically all blocks have fixed size and there is no other data all >>> parity information will end-up on one (z1) or two (z2) specific disks? >>> >> No. There are always smaller writes to metadata that will distribute parity. >> What is the total width of your raidz1 stripe? >> >> > > 4x disks, 16KB recordsize, 128GB file, random read with 16KB block. >From what I gather each 16KB record (plus parity) is spread across the raidz >disks. This causes the total random IOPS (write AND read) of the raidz to be >that of the slowest disk in the raidz. Raidz is definitely made for sequential IO patterns not random. To get good random IO with raidz you need a zpool with X raidz vdevs where X = desired IOPS/IOPS of single drive. -Ross _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
