[OpenIndiana-discuss] measuring fragmentation on ZFS?

[Roy Sigurd Karlsbakk]

> Is there a way to query how much fragmentation there is in a
> filesystem?
> 
> We've got a large filesystem which was allowed to get really full
> before it was expanded considerably, and we also had deduplication
> turned on briefly, which caused the dedupe table to get very, very
> big. While the application that stores data rewrites a lot of it, the
> dedupe table still has a lot of entries in it, etc.

If the filesystem was filled up, and you added another VDEV, the initial VDEV(s) will stay full until you either destroy the pool, replace the drives with larger ones (given autoexpand=on) or wait for block pointer rewrite, which may take a while....

I'm replacing 2TB drives with 3TB ones atm for the same reason - the initial 30TB pool got filled up and we attached another disk chassis - this didn't help much, performance-wise, so we ended up getting 22 3TB drives to fix it the hard way - backing up and restoring what now is 35TB is not very amusing...

Vennlige hilsener / Best regards

roy
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Roy Sigurd Karlsbakk
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roy at karlsbakk.net
http://blogg.karlsbakk.net/
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