Re: [zfs-discuss] ZVOL vs regular fs — huge difference in data consumption

Gordan Bobic gordan.bobic at gmail.com
Fri May 17 11:09:17 EDT 2013


I suspect what's going on is that your zvol is seeing the 4KB sector NTFS
as a bunch of 4KB files.


On Fri, May 17, 2013 at 4:05 PM, Daniel Smedegaard Buus <
danielbuus at gmail.com> wrote:

> Hi :)
>
> I have this bunch of small sample files (50+ gigs worth) that I've
> previously shared via NFS to my Hackintosh where I play around with making
> music.
>
> The FS I created for it is a regular zfs one, just with gzip-9 compression
> added to the mix.
>
> The zpool is quite massive, so my recordsize is 128k, which I've assumed
> meant that I was wasting a bunch of space on smaller files. But now I'm not
> so sure.
>
> I've been playing around with SCST and ZVOLs and wanted to move all these
> samples onto a ZVOL formatted with NTFS (4k sectors) (so I can also mount
> it in Windows). I created the zvol with gzip-9 compression as well, and I
> was kind of expecting to see the end result being less space consumed than
> with the regular ZFS fs.
>
> Not so. In fact, I created this ZVOL with -V 60G, but references,
> usedbydataset, and written all say 64.5 GB, whereas the regular ZFS FS uses
> 52.6 GB.
>
> What am I missing here? Probably a lot, so if you can, please educate me!
> I just don't get it!
>
> My properties on the zvol and filesystem:
>
> NAME                   PROPERTY              VALUE                  SOURCE
> titanic/zvol-composer  type                  volume                 -
> titanic/zvol-composer  creation              Sun May 12 11:56 2013  -
> titanic/zvol-composer  used                  64.5G                  -
> titanic/zvol-composer  available             343G                   -
> titanic/zvol-composer  referenced            64.5G                  -
> titanic/zvol-composer  compressratio         1.05x                  -
> titanic/zvol-composer  reservation           none                   default
> titanic/zvol-composer  volsize               60G                    local
> titanic/zvol-composer  volblocksize          32K                    -
> titanic/zvol-composer  checksum              on                     default
> titanic/zvol-composer  compression           gzip-9                 local
> titanic/zvol-composer  readonly              off                    default
> titanic/zvol-composer  copies                1                      default
> titanic/zvol-composer  refreservation        none                   local
> titanic/zvol-composer  primarycache          all
>  inherited from titanic
> titanic/zvol-composer  secondarycache        all                    default
> titanic/zvol-composer  usedbysnapshots       0                      -
> titanic/zvol-composer  usedbydataset         64.5G                  -
> titanic/zvol-composer  usedbychildren        0                      -
> titanic/zvol-composer  usedbyrefreservation  0                      -
> titanic/zvol-composer  logbias               latency                default
> titanic/zvol-composer  dedup                 off                    default
> titanic/zvol-composer  mlslabel              none                   default
> titanic/zvol-composer  sync                  standard               default
> titanic/zvol-composer  refcompressratio      1.05x                  -
> titanic/zvol-composer  written               64.5G                  -
> titanic/zvol-composer  snapdev               hidden                 default
>
> NAME                 PROPERTY              VALUE                  SOURCE
> titanic/Systems/Dex  type                  filesystem             -
> titanic/Systems/Dex  creation              Wed Apr 24 19:07 2013  -
> titanic/Systems/Dex  used                  52.6G                  -
> titanic/Systems/Dex  available             343G                   -
> titanic/Systems/Dex  referenced            52.6G                  -
> titanic/Systems/Dex  compressratio         1.07x                  -
> titanic/Systems/Dex  mounted               yes                    -
> titanic/Systems/Dex  quota                 none                   default
> titanic/Systems/Dex  reservation           none                   default
> titanic/Systems/Dex  recordsize            128K                   default
> titanic/Systems/Dex  mountpoint            /titanic/Systems/Dex
> inherited from titanic
> titanic/Systems/Dex  sharenfs              off
>  inherited from titanic
> titanic/Systems/Dex  checksum              on                     default
> titanic/Systems/Dex  compression           gzip-9                 local
> titanic/Systems/Dex  atime                 off
>  inherited from titanic
> titanic/Systems/Dex  devices               on                     default
> titanic/Systems/Dex  exec                  on                     default
> titanic/Systems/Dex  setuid                on                     default
> titanic/Systems/Dex  readonly              off                    default
> titanic/Systems/Dex  zoned                 off                    default
> titanic/Systems/Dex  snapdir               hidden                 default
> titanic/Systems/Dex  aclinherit            restricted             default
> titanic/Systems/Dex  canmount              on                     default
> titanic/Systems/Dex  xattr                 on                     default
> titanic/Systems/Dex  copies                1                      default
> titanic/Systems/Dex  version               4                      -
> titanic/Systems/Dex  utf8only              off                    -
> titanic/Systems/Dex  normalization         none                   -
> titanic/Systems/Dex  casesensitivity       sensitive              -
> titanic/Systems/Dex  vscan                 off                    default
> titanic/Systems/Dex  nbmand                off                    default
> titanic/Systems/Dex  sharesmb              off                    default
> titanic/Systems/Dex  refquota              none                   default
> titanic/Systems/Dex  refreservation        none                   default
> titanic/Systems/Dex  primarycache          all
>  inherited from titanic
> titanic/Systems/Dex  secondarycache        all                    default
> titanic/Systems/Dex  usedbysnapshots       0                      -
> titanic/Systems/Dex  usedbydataset         52.6G                  -
> titanic/Systems/Dex  usedbychildren        0                      -
> titanic/Systems/Dex  usedbyrefreservation  0                      -
> titanic/Systems/Dex  logbias               latency                default
> titanic/Systems/Dex  dedup                 off                    default
> titanic/Systems/Dex  mlslabel              none                   default
> titanic/Systems/Dex  sync                  standard               default
> titanic/Systems/Dex  refcompressratio      1.07x                  -
> titanic/Systems/Dex  written               52.6G                  -
> titanic/Systems/Dex  snapdev               hidden                 default
>
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