[linux-lvm] Data deduplication for Linux : lessfs
Mark Ruijter
mruijter at gmail.com
Wed Jun 24 19:25:56 UTC 2009
Hi Roy,
>
> It's a good idea, but given the current traffic on the lessfs mailing
> list, I'm not sure if much work is done. I have been a member of that
> list since June 1 and haven't received more than one message, which
> was the one I wrote myself.
>
Almost all the traffic is on the forum - open discussion.
Only one person posted to the mailing list. ;-)
> If done smartly, this may perhaps be possible, but the problem is the
> filesystem's metadata. Is this going to be dedup'ed? How much will
> this take? A simple backup will update atime on all the files backed
> up, and although atime isn't always wanted or needed, the problem
> occurs elsewhere.
Typically the meta data on production systems is approx 10%~20% of the
deduplicated stored data.
Stored data is on my systems 40x less then the data written to the
filesystem.
For example, from a real life backup server making dozens of backups
each day:
# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/cciss/c0d0p3 9.7G 2.4G 6.9G 26% /
/dev/cciss/c0d0p1 99M 23M 72M 24% /boot
tmpfs 7.9G 0 7.9G 0% /dev/shm
/dev/cciss/c0d0p4 246G 6.0G 241G 3% /meta
/dev/cciss/c0d1p1 274G 73G 202G 27% /blockdata
/dev/cciss/c1d0p1 4.1T 1.5T 2.7T 35% /data
lessfs 4.1T 1.5T 2.7T 35% /pooldata
[root at lessfssrv pooldata]# du . -s -h
31T .
[root at lessfssrv pooldata]# ls -alh /data/current/
total 314G
drwxr-xr-x 2 root root 26 Jun 1 00:12 .
drwxr-xr-x 6 root root 59 Jun 1 00:12 ..
-rw-r--r-- 1 root root 314G Jun 22 14:26 blockdata.tch
[root at lessfssrv pooldata]# ls -alh /meta/current/
total 1.4G
drwxr-xr-x 2 root root 63 Jun 1 00:12 .
drwxr-xr-x 6 root root 59 Jun 1 00:12 ..
-rw-r--r-- 1 root root 1.3G Jun 22 14:52 blockusage.tch
-rw-r--r-- 1 root root 89M Jun 22 14:45 dirent.tcb
-rw-r--r-- 1 root root 89M Jun 22 14:52 metadata.tcb
Mark.
>
>
> roy
> --
> Roy Sigurd Karlsbakk
> (+47) 97542685
> roy at karlsbakk.net
> http://blogg.karlsbakk.net/
> --
> I all pedagogikk er det essensielt at pensum presenteres
> intelligibelt. Det er et elementært imperativ for alle pedagoger å
> unngå eksessiv anvendelse av idiomer med fremmed opprinnelse. I de
> fleste tilfeller eksisterer adekvate og relevante synonymer på norsk.
>
>
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