[OmniOS-discuss] Fragmentation
Guenther Alka
alka at hfg-gmuend.de
Fri Jun 23 15:25:25 UTC 2017
Yes, but
If you increase your pool by adding a new vdev, your current data are
not auto-rebalanced. This will only happen over time with new or
modified data.
If you want the best performance then, you must copy over current data
ex by renaming a filesystem, replicate it to the former name and delete
it then.
Gea
Am 23.06.2017 um 17:19 schrieb Artyom Zhandarovsky:
> So basically i need to add just more drives... ?
>
> 2017-06-23 18:09 GMT+03:00 Guenther Alka <alka at hfg-gmuend.de
> <mailto:alka at hfg-gmuend.de>>:
>
> 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
> <https://utcc.utoronto.ca/%7Ecks/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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