Hi Robert, I read the following section from http://blogs.sun.com/roch/entry/when_to_and_not_to as indicating random writes to a RAID-Z had the performance of a single disk regardless of the group size:
Effectively, as a first approximation, an N-disk RAID-Z group will behave as a single device in terms of delivered random input IOPS. Thus a 10-disk group of devices each capable of 200-IOPS, will globally act as a 200-IOPS capable RAID-Z group.
Best Regards, Jason On 1/10/07, Robert Milkowski <[EMAIL PROTECTED]> wrote:
Hello Jason, Wednesday, January 10, 2007, 10:54:29 PM, you wrote: JJWW> Hi Kyle, JJWW> I think there was a lot of talk about this behavior on the RAIDZ2 vs. JJWW> RAID-10 thread. My understanding from that discussion was that every JJWW> write stripes the block across all disks on a RAIDZ/Z2 group, thereby JJWW> making writing the group no faster than writing to a single disk. JJWW> However reads are much faster, as all the disk are activated in the JJWW> read process. The opposite actually. Because of COW, writing (modifying as well) will give you up-to N-1 disks performance for raid-z1 and N-2 disks performance for raid-z2. Howeer reading can be slow in case of many small random reads as to read each fs block you've got to wait for all data disks in a group. JJWW> The default config on the X4500 we received recently was RAIDZ-groups JJWW> of 6 disks (across the 6 controllers) striped together into one large JJWW> zpool. However the problem with that config is lack of hot-spare. Of course it depends what you want (and there was no hot spare support in U2 which is os installed in factory so far). -- Best regards, Robert mailto:[EMAIL PROTECTED] http://milek.blogspot.com
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