read/write benchmarking: UFS2 vs ZFS vs EXT3 vs ZFS RAIDZ vs
Linux MDRAID
Nathanael Hoyle
nhoyle at hoyletech.com
Sun Jun 28 17:54:28 UTC 2009
<entire previous conversation snipped, in part due to top-posting;
removed geom from CC since this post doesn't reference it>
The clear distinction between the two sets of performance tests you two
have done is that Dan's are highly random short i/o's, and Andrew's are
large sequential transfers. Large sequential transfers necessarily
engage all of the disks in the pool, regardless of the parity strategy,
therefore the implied penalty for ZFS to read the parity data from all
drives is mostly theoretical, and actually performs more like RAID 5
typically would. In the case of Dan's highly random, short i/o's, the
read itself is trivial, making the overhead of spinning/seeking all the
disks to calculate the full checksum and validate it inordinately high.
The implication of these two benchmarks is clear as well: ZFS RAIDZ may
be an excellent choice for large storage capacity with reasonable
performance characteristics for large sequential workloads, but should
be avoided where many small transfers will be occurring.
-Nathanael
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