[OpenIndiana-discuss] experimental or otherwise not recommended options for ZFS

[Gary Gendel]

Jan,

I'm not sure that turning dedup or compression on is useful in your 
particular situation.

Since the images are already compressed, re-compressing them only adds 
cpu overhead without much benefit. Also, Since images will have little 
opportunity for dedup (unless you tend to have multiple and exact 
copies) it just wastes cpu cycles and uses up lots of memory.  Unless 
there is some other data you expect to offset the compressibility and 
replication of images, I wouldn't bother with these options.

Gary

On 1/30/12 11:01 AM, Jan Owoc wrote:
> Thank you for the replies.
>
> On Sun, Jan 29, 2012 at 11:33 PM, Sašo Kiselkov<skiselkov.ml at gmail.com>  wrote:
>> The obvious saying springs to mind: "RAID != backup". If you need your
>> data to be safe, have two copies of it in two geographically separate
>> locations running in two separate machines.
> I've read about ECC/non-ECC and RAID != backup and already decided on
> a solution - I wanted some indication of the stability of the ZFS
> features themselves. My question arose when I read that
> "dedup=fletcher4,verify" was causing problems [1] and was removed. I
> was looking for indications whether choosing "checksum=sha256,
> compression=on, dedup=verify" in itself was asking for trouble.
>
> [1] http://mail.opensolaris.org/pipermail/zfs-discuss/2009-November/034106.html
>
> On Sun, Jan 29, 2012 at 10:38 PM, Robbie Crash
> <sardonic.smiles at gmail.com>  wrote:
>> Those features are thoroughly tested and not experimental. That said:
>> nothing is guaranteed to keep your data safe, and if you're truly worried
>> about it, don't use dedupe.
> Because photos tend to be already compressed, and I have only ~5%
> duplicates, I will probably only change "checksum=sha256" from its
> default. Other than CPU time, is there any other reason I may want to
> stick with the default of "checksum=on" (fletcher4)?
>
> Once again, thank you for the insight,
> Jan
>
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