> It's the block checksum that requires reading all of the disks. If
> ZFS stored sub-block checksums for the RAID-Z case then short reads
> could often be satisfied without reading the whole block (and all
> disks).
What happens when a sub-block is missing (single disk failure)? Surely
it doesn
>So actually I mis-spoke slightly; rather than "all disks", I should
>have said "all data disks."
>In practice this has the same effect: No more than one read may be
>processed at a time.
But aren't short blocks sometimes stored on only a subset of disks?
Casper
_
On Jan 4, 2007, at 3:25 AM, [EMAIL PROTECTED] wrote:
Is there some reason why a small read on a raidz2 is not
statistically very
likely to require I/O on only one device? Assuming a non-degraded
pool of
course.
ZFS stores its checksums for RAIDZ/RAIDZ2 in such a way that all
disks must b
Hello Anton,
Thursday, January 4, 2007, 3:46:48 AM, you wrote:
>> Is there some reason why a small read on a raidz2 is not statistically very
>> likely to require I/O on only one device? Assuming a non-degraded pool of
>> course.
ABR> ZFS stores its checksums for RAIDZ/RAIDZ2 in such a way tha
>> Is there some reason why a small read on a raidz2 is not statistically very
>> likely to require I/O on only one device? Assuming a non-degraded pool of
>> course.
>
>ZFS stores its checksums for RAIDZ/RAIDZ2 in such a way that all disks must be
>read to compute and
verify the checksum.
B
> Is there some reason why a small read on a raidz2 is not statistically very
> likely to require I/O on only one device? Assuming a non-degraded pool of
> course.
ZFS stores its checksums for RAIDZ/RAIDZ2 in such a way that all disks must be
read to compute and verify the checksum.
This me
