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Re: [Networker] ZFS deduplication.
2010-03-18 12:22:39
This is from the thread where we discussed this. The block size is 128K.
root@ukmdsr3cora04:/zfstank/DEDUP# zfs get all zfstank
NAME PROPERTY VALUE SOURCE
zfstank type filesystem -
zfstank creation Wed Mar 3 13:10 2010 -
zfstank used 8.17G -
zfstank available 59.1G -
zfstank referenced 24K -
zfstank compressratio 1.00x -
zfstank mounted yes -
zfstank quota none default
zfstank reservation none default
zfstank recordsize 128K default
zfstank mountpoint /zfstank default
zfstank sharenfs off default
I asked him: "Can you go into the AFTD properties and modify the
block size to be 128K and see if that makes any difference ? " and his
answer was "It already is. I set that when I created the device.".
As I said, I suspect that files within the save stream are not
aligned in such a way that they start at block boundaries because of
the meta-data which is part of the saveset.
Terry Lemons wrote:
Hi Yaron
I know that NetWorker has a default block size for each of its output devices.
This default block size can be overridden; details on this are in the NetWorker
Administration Guide.
Does ZFS have a specific block size that it deduplicates? If so, could it be
that the NetWorker default block size for the AFTD device is not the same as,
or a multiple of, the ZFS default block size?
tl
-----Original Message-----
From: EMC NetWorker discussion [mailto:NETWORKER AT LISTSERV.TEMPLE DOT EDU] On
Behalf Of Yaron Zabary
Sent: Sunday, March 14, 2010 3:59 PM
To: NETWORKER AT LISTSERV.TEMPLE DOT EDU
Subject: [Networker] ZFS deduplication.
A few days ago I read a post to EMC's Networker forum by Nicholas
Bone (https://community.emc.com/thread/99839?tstart=0). He reported a
test he performed with AFTD which was running on top of ZFS with dedup.
Unfortunately, he wasn't able to get any reasonable dedup ratios (1.03
for three full savesets of the the same file system). My conclusion was
that Networker does not align files at block level, which confuses the
ZFS dedup code. Is anyone familiar with some flag or any configuration
option which will convince save or AFTD to do the right thing so that
ZFS will be able to find identical blocks ?
--
-- Yaron.
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