[OpenIndiana-discuss] ZFS improvements.

Maurilio Longo maurilio.longo at libero.it
Tue Nov 23 16:07:53 UTC 2010


as I said, it seems the same "problem" happens on filesystems (which are 128Kb
 by default), where you have a lot of small files.

Maybe if you store dvd images only you don't incur in this wastage of space :)

> My problem with the ashift=9 on 4KB sectored drives is that a write of 512B
> incurs an enormous hit to latency because the drive is physically reading
> 4KB, modifying 512B, and writing 4KB. Which also means that there is the

Those 4Kb disk are slow by themselves, I mean, they're good to build "slow"
backup systems only, imho.

> potential for an error to be made during this operation, silently corrupting
> your data.

I think that you don't risk corruption, since zfs checksums everything.

A zfs filesystem, here on 512b, with solaris nevada version 143 source code
and compiled modules

maurilio at krumiro:~$ zfs get all iscsi/snv_143
NAME           PROPERTY               VALUE                  SOURCE
iscsi/snv_143  type                   filesystem             -
iscsi/snv_143  creation               ven ago 13 10:14 2010  -
iscsi/snv_143  used                   2,73G                  -
iscsi/snv_143  available              979G                   -
iscsi/snv_143  referenced             2,73G                  -
iscsi/snv_143  compressratio          1.76x                  -
iscsi/snv_143  mounted                yes                    -
iscsi/snv_143  quota                  none                   default
iscsi/snv_143  reservation            none                   default
iscsi/snv_143  recordsize             128K                   default
iscsi/snv_143  mountpoint             /iscsi/snv_143         default
iscsi/snv_143  sharenfs               off                    default
iscsi/snv_143  checksum               on                     default
iscsi/snv_143  compression            on                     local
iscsi/snv_143  atime                  off                    local
iscsi/snv_143  devices                on                     default
iscsi/snv_143  exec                   on                     default
iscsi/snv_143  setuid                 on                     default
iscsi/snv_143  readonly               off                    default
iscsi/snv_143  zoned                  off                    default
iscsi/snv_143  snapdir                hidden                 default
iscsi/snv_143  aclinherit             restricted             default
iscsi/snv_143  canmount               on                     default
iscsi/snv_143  xattr                  on                     default
iscsi/snv_143  copies                 1                      default
iscsi/snv_143  version                4                      -
iscsi/snv_143  utf8only               off                    -
iscsi/snv_143  normalization          none                   -
iscsi/snv_143  casesensitivity        sensitive              -
iscsi/snv_143  vscan                  off                    default
iscsi/snv_143  nbmand                 off                    default
iscsi/snv_143  sharesmb               off                    default
iscsi/snv_143  refquota               none                   default
iscsi/snv_143  refreservation         none                   default
iscsi/snv_143  primarycache           all                    default
iscsi/snv_143  secondarycache         all                    default
iscsi/snv_143  usedbysnapshots        0                      -
iscsi/snv_143  usedbydataset          2,73G                  -
iscsi/snv_143  usedbychildren         0                      -
iscsi/snv_143  usedbyrefreservation   0                      -
iscsi/snv_143  logbias                throughput             inherited from
iscsi/snv_143  dedup                  off                    default
iscsi/snv_143  mlslabel               none                   default
iscsi/snv_143  sync                   standard               default
iscsi/snv_143  com.sun:auto-snapshot  false                  inherited from

here on 4Kb

maurilio at rsync:~$ zfs get all nas/test/snv_143
NAME              PROPERTY              VALUE                  SOURCE
nas/test/snv_143  type                  filesystem             -
nas/test/snv_143  creation              lun nov 22 11:12 2010  -
nas/test/snv_143  used                  3,81G                  -
nas/test/snv_143  available             312G                   -
nas/test/snv_143  referenced            3,81G                  -
nas/test/snv_143  compressratio         1.76x                  -
nas/test/snv_143  mounted               yes                    -
nas/test/snv_143  quota                 none                   default
nas/test/snv_143  reservation           none                   default
nas/test/snv_143  recordsize            128K                   default
nas/test/snv_143  mountpoint            /nas/test/snv_143      default
nas/test/snv_143  sharenfs              off                    default
nas/test/snv_143  checksum              on                     default
nas/test/snv_143  compression           on                     inherited from
nas/test/snv_143  atime                 on                     default
nas/test/snv_143  devices               on                     default
nas/test/snv_143  exec                  on                     default
nas/test/snv_143  setuid                on                     default
nas/test/snv_143  readonly              off                    default
nas/test/snv_143  zoned                 off                    default
nas/test/snv_143  snapdir               hidden                 default
nas/test/snv_143  aclinherit            restricted             default
nas/test/snv_143  canmount              on                     default
nas/test/snv_143  xattr                 on                     default
nas/test/snv_143  copies                1                      default
nas/test/snv_143  version               4                      -
nas/test/snv_143  utf8only              off                    -
nas/test/snv_143  normalization         none                   -
nas/test/snv_143  casesensitivity       sensitive              -
nas/test/snv_143  vscan                 off                    default
nas/test/snv_143  nbmand                off                    default
nas/test/snv_143  sharesmb              off                    default
nas/test/snv_143  refquota              none                   default
nas/test/snv_143  refreservation        none                   default
nas/test/snv_143  primarycache          all                    default
nas/test/snv_143  secondarycache        all                    default
nas/test/snv_143  usedbysnapshots       0                      -
nas/test/snv_143  usedbydataset         3,81G                  -
nas/test/snv_143  usedbychildren        0                      -
nas/test/snv_143  usedbyrefreservation  0                      -
nas/test/snv_143  logbias               latency                default
nas/test/snv_143  dedup                 off                    default
nas/test/snv_143  mlslabel              none                   default
nas/test/snv_143  sync                  standard               default

Here, even with a lot better compression we use 3,81Gb instead of 2,73

Best regards.


|  |  | |__| Maurilio Longo
|_|_|_|____| farmaconsult s.r.l.

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