ZFS space consumption

[Nuts Bastogne]

Hi Stefan,

Thanks for your answer.

The compressratio and refcompressratio are :
compressratio         1.05x
refcompressratio      1.07x

Maybe i'm wrong but i don't think this ii related to my "issue" and if i
understand well, the compression should decreased the space used property
not the logicalused property.

Le lun. 27 mai 2019 à 13:47, Stefan Esser <se at freebsd.org> a écrit :

> Am 27.05.19 um 11:55 schrieb Nuts Bastogne:
> > Hi All,
> >
> > I'm confused about the zfs consumption of space.
> >
> > I'm using ZFS to create clone from a sysprep and use it as a zvol for  vm
> > connected via iscsi.
> > The zvol has a size of 256GB.
> > But several dataset have a space comsuption bigger than the size of the
> > zvol.
> > I thought this could be happen when we use snapshot but this is not my
> case.
> >
> > here information from one zvol impacted :
> > type                  volume
> > volsize               256G
> > used                  483G
> > referenced            507G
> > copies                1
> > refreservation        none
> > compression           lz4
>
> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>
> Might that be the answer?
>
> Look at the current compression ratio ...
>
> > usedbydataset         483G
> > written               483G
> > logicalused           238G
> > logicalreferenced     251G
> >
> > logicalused and logicalreferenced are correct, so the vm didnt see a disk
> > bigger than 256GB.
> > As used, usedbydataset, referenced properties don't include metadata
> > neither snapshot i dont'know what it could be.
> >
> > After some research on the web some people had the same issue du to the
> > blocksize of their disk and had to change the ashift to 12. but this is
> our
> > configuration already.
> >
> > disk : (from diskinfo -v)
> > SSD
> >  512         # sectorsize
> > 3840755982336 # mediasize in bytes (3.5T)
> > 7501476528   # mediasize in sectors
> > 4096         # stripesize
> >
> > volblocksize = 16k
> > ashift = 12
> >
> > What i can check to go deeper on this issue ?
> > or this is just a normal behavior du to my configuration ?
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>