[OmniOS-discuss] Fragmentation

[Guenther Alka]

The fragmentation info does not describe the fragmentation of the data 
on pool but the fragmentation of the free space.  A high fragmentation 
value will result in high data fragmentation only when you write or 
modify data.

https://utcc.utoronto.ca/~cks/space/blog/solaris/ZFSZpoolFragmentationMeaning
So the best and only way to reduce data fragmentation is not to fill up 
a pool say over 70-80%.

You should also know that CopyOnWrite filesystems where a complete 
datablock ex 128k is written newly even if you change a "house" to a 
"mouse" in a textfile are more vulnerable to fragmentation than older 
filesystems. This is the price for the crash resitency where a power 
outage during a write cannot lead to a corrupted filesystem like with 
older filesystems where it can happen that the data is modified "infile" 
while the according metadata update is not happening. ZFS 
over-compensates this with its advanced rambased read and write caches. 
A "defrag tool" is not available for ZFS.

Gea


Am 23.06.2017 um 16:13 schrieb Artyom Zhandarovsky:
> there any way to decrease fragmentation of dr_tank ?

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