So if the ZFS checksum is set to fletcher4 at the pool level, and
dedup=on, which checksum will it be using?

If I attempt to set dedup=fletcher4, I do indeed get this:

cannot set property for 'zp': 'dedup' must be one of 'on | off | verify
| sha256[,verify]'

Could it be that my performance troubles are due to the calculation of
two different checksums?

Thanks,
Chris

-----Original Message-----
From: cyril.pli...@gmail.com [mailto:cyril.pli...@gmail.com] On Behalf
Of Cyril Plisko
Sent: 16 December 2009 17:09
To: Andrey Kuzmin
Cc: Chris Murray; zfs-discuss@opensolaris.org
Subject: Re: [zfs-discuss] Troubleshooting dedup performance

>> I've set dedup to what I believe are the least resource-intensive
>> settings - "checksum=fletcher4" on the pool, & "dedup=on" rather than
>
> I believe checksum=fletcher4 is acceptable in dedup=verify mode only.
> What you're doing is seemingly deduplication with weak checksum w/o
> verification.

I think fletcher4 use for the deduplication purposes was disabled [1]
at all, right before build 129 cut.


[1]
http://hg.genunix.org/onnv-gate.hg/diff/93c7076216f6/usr/src/common/zfs/
zfs_prop.c


-- 
Regards,
        Cyril

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