On Oct 2, 2009, at 7:46 AM, Ray Clark wrote:
Replying to relling's October 1, 2009 3:34 post:
Richard, regarding "when a pool is created, there is only metadata
which uses fletcher4". Was this true in U4, or is this a new change
of default with U4 using fletcher2? Similarly, did the Ubberblock
use sha256 in U4? I am running U4.
ZFS uses different checksums for different things. Briefly,
use checksum
---------------------------------------------------------
uberblock SHA-256, self-checksummed
labels SHA-256
metadata fletcher4
data fletcher2 (default), set with checksum parameter
ZIL log fletcher2, self-checksummed
gang block SHA-256, self-checksummed
The parent holds the checksum for an entity is not self-checksummed.
The big question, that is currently unanswered, is do we see single
bit faults in disk-based storage systems? The answer to this question
must be known before the effectiveness of a checksum can be evaluated.
The overwhelming empirical evidence suggests that fletcher2 catches
many storage system corruptions.
-- richard
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