As zvol uses the space in the zpool?

There are storadzh on freenas create zvol and iscsi I announce.
Looked all over documnetation( docs.oracle.com/cd/E19253-01/820-0836 ), but I can't understand how this zvol uses the space in the zpool ?

For example I have created here is a zvol on 4 Tb
under the name data/hv-data.

Writing there 1 Tb I can see that it takes 5 TB
1465484014764.png
how does it work ?
what values do the fields
AVAIL USED USEDSNAP USEDDS USEDREFRESERV USEDCHILD
?

Here properties more
1465484939850.png

and descriptions such as it is docs.oracle.com/cd/E19253-01/820-0836/gazsd/index.html
but the clarity is still not making.
July 8th 19 at 15:39
2 answers
July 8th 19 at 15:41
Dynamically. As needed.
You can have 10 zvol on the zpool of 1 TB.
And that's what the first of these 10 zvol will take the terabytes, and sneakers.
A designated space is reserved, it really is in the pool, or is it abstraction ?
For example 10tb pool
I create zvol size of 4 tb and pour on it 1 tb of data.
How many in the pool will remain a real place ? - Santos.Stehr46 commented on July 8th 19 at 15:44
: think I figured it out.
well found docs.oracle.com/cd/E19253-01/820-0836/gazvb/index.html
and if someone first, and sneakers, it is discharged that includes:
docs.oracle.com/cd/E19253-01/820-0836/gcfhk/index.html - Santos.Stehr46 commented on July 8th 19 at 15:47
no. not to the thin. the place is not reserved, if you have created a zvol with default settings. - Rachel_Considine commented on July 8th 19 at 15:50
: well, apparently I have by default is reserved. And the documentation says that reserverade. - Santos.Stehr46 commented on July 8th 19 at 15:53
: just checked. moved the files from one zvol, which occupied 76% of the disk to a different zvol. old decreased. new rose.

the truth is I have a pure FreeBSD, not FreeNAS. maybe FreeNAS some of his default settings. - Rachel_Considine commented on July 8th 19 at 15:56
: By default, when you create a volume reserved space equal to the volume size. Although this is not recommended, you can create a sparse volume by setting the-s flag for the command zfs create-V or by changing the reserved space after you create the volume.
docs.oracle.com/cd/E19253-01/820-0836/gcfhk/index.html - Santos.Stehr46 commented on July 8th 19 at 15:59
:
For example I have created here is a zvol on 4 Tb
under the name data/hv-data.

Writing there 1 Tb I can see that it takes 5 TB


And this is certainly the estimate with the data compression. On this zvol compression is enabled, I suppose? - Rachel_Considine commented on July 8th 19 at 16:02
:
Although this is not recommended, you can create a sparse volume by setting the-s flag for the command zfs create-V or by changing the reserved space after you create the volume.


Well that's clear what we have with you the difference:
I never indicated the size of the ZFS volume when it is created. - Rachel_Considine commented on July 8th 19 at 16:05
: compression not.
1)what size will each iscsi if you don't specify the size ? Pool size ? (me does not allow to create zvol without a size)
2) As I understand the size of the zvol != the quota for him. And in fact, the reservation is simply a guarantee that the pool will place the size of the zvol ?
In the screenshot above I gave an example of the volume hv-data.
Its size == 4–Ęb this can be seen in the properties. It is written information on ~0.9 Tb in the column used 4.97 Tb . Ie 4t zvol reserved, but the date still pishitsya shared array ? - Santos.Stehr46 commented on July 8th 19 at 16:08
: iSCSI is a block device. One who is connected to it, your file system is doing. The size must be specified.

I mean the file system that are made inside operating system and distributed via NFS or Samba, not iSCSCI. There I never specify the size. Who was the first time to capture the physical location, and sneakers. - Rachel_Considine commented on July 8th 19 at 16:11
: Well in that case, all that you described above applies to the normal data set, not a zvol. And to my main question does not apply. - Santos.Stehr46 commented on July 8th 19 at 16:14
July 8th 19 at 15:43
I recommend reading "FreeBSD Mastery: ZFS" by Michael W. Lucas, Allan Jude.
In detail and clearly set out what and how.
In Russian there is no such ?))
From English not very ( - Santos.Stehr46 commented on July 8th 19 at 15:46
: Do not know, to be honest. - Santos.Stehr46 commented on July 8th 19 at 15:49

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