On Thu, 2011-04-28 at 14:33 -0700, Brandon High wrote:
> On Wed, Apr 27, 2011 at 9:26 PM, Edward Ned Harvey
> <opensolarisisdeadlongliveopensola...@nedharvey.com> wrote:
> > Correct me if I'm wrong, but the dedup sha256 checksum happens in addition
> > to (not instead of) the fletcher2 integrity checksum. So after bootup,
>
> My understanding is that enabling dedup forces sha256.
>
> "The default checksum used for deduplication is sha256 (subject to
> change). When dedup is enabled, the dedup checksum algorithm overrides
> the checksum property."
>
> -B
>
>From the man page for zfs(1)
dedup=on | off | verify | sha256[,verify]
Controls whether deduplication is in effect for a
dataset. The default value is off. The default checksum
used for deduplication is sha256 (subject to change).
When dedup is enabled, the dedup checksum algorithm
overrides the checksum property. Setting the value to
verify is equivalent to specifying sha256,verify.
If the property is set to verify, then, whenever two
blocks have the same signature, ZFS will do a byte-for-
byte comparison with the existing block to ensure that
the contents are identical.
This is from b159.
A careful reading of the man page seems to imply that there's no way to
change the dedup checksum algorithm from sha256, as the dedup property
ignores the checksum property, and there's no provided way to explicitly
set a checksum algorithm specific to dedup (i.e. there's no way to
override the default for dedup).
--
Erik Trimble
Java System Support
Mailstop: usca22-317
Phone: x67195
Santa Clara, CA
Timezone: US/Pacific (GMT-0800)
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