Re: [zfs-fuse] ZFS compression question

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Emmanuel Anne

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Dec 30, 2013, 2:51:56 AM12/30/13
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When did you enable compression ?
Because if you filled your drive until 92% and then enabled compression, what was written before didn't change, just the remaining 5% and something were compressed.
For df it's very unprecise with compression, and with zfs it's better to leave more than 5% of free space if you don't want to risk a huge slowdown.


2013/12/30 <realw...@gmail.com>
Hi,

I have a newbie question.  I have a pool which is a single drive /sda1

I have compression enabled on this drive.  I know the compression ratio:

zfs get compressratio /ssd/mnt

NAME     PROPERTY       VALUE  SOURCE
ssd/mnt  compressratio  1.92x  -

So, why does 'df' not show any extra space, and when I use 'zfs list', REFER shows the same as used?

NAME      USED  AVAIL  REFER  MOUNTPOINT
ssd      97.6G   340G    31K  /ssd
ssd/mnt  97.6G   340G  97.6G  /ssd/mnt


My drive started with 450 GB (around) and still looks to have gained no space:

df
ssd            355967104         0 355967104   0% /ssd
ssd/mnt        458289792 102322688 355967104  23% /ssd/mnt


If I have 97GB with 1.92x compression, surely disk space should be around 50GB, leaving 400GB free.

I must be missing something fundamental here... perhaps someone can explain?

Many thanks,

RW

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