fractional reserve space not reclaim

chinchillaking · ‎2011-09-29

Dear All,

ev1 volume with 1TB without snap space reserve, I try delete all snapshot in volume ev1 but "reserved" did not reclaim space when I type df -r , anyone face this issue before?

===== SIS STAT =====
Path Allocated Saving %Saved
/vol/ev1 801 GB 3686 MB 0 %

/vol/ev1/ev1.lun           861.0g (924521472000) (r/w, online, mapped)
          Comment:
          Serial#: P3WYiJSeTf/E
          Share: none
          Space Reservation: enabled
          Multiprotocol Type: windows

===== DF-R =====
Filesystem                        kbytes                used                     avail                  reserved            Mounted on
/vol/ev1/                            1073741824      1070461388         3280436            168618224       /vol/ev1/
/vol/ev1/.snapshot            0                         0                          0                         0                      /vol/ev1/.snapshot

===== SNAP-RESERVE =====
Volume ev1: current snapshot reserve is 0% or 0 k-bytes

===== SNAP-LIST-N =====
Volume vol0
working...

date name
------------ --------
Volume ev1
working...

No snapshots exist

ev1 online          raid_dp, flex     nosnap=on, nosnapdir=off,
                                sis               minra=off, no_atime_update=off,
                                                  nvfail=off,
                                                  ignore_inconsistent=off,
                                                  snapmirrored=off,
                                                  create_ucode=on,
                                                  convert_ucode=on,
                                                  maxdirsize=41861,
                                                  schedsnapname=ordinal,
                                                  fs_size_fixed=off,
                                                  compression=off,
                                                  guarantee=volume, svo_enable=off,
                                                  svo_checksum=off,
                                                  svo_allow_rman=off,
                                                  svo_reject_errors=off,
                                                  no_i2p=off,
                                                  fractional_reserve=20,
                                                  extent=off,
                                                  try_first=volume_grow,
                                                  sis_logging=on, read_realloc=off,
                                                  snapshot_clone_dependency=on

Best regards,

Chung

peter_lehmann · ‎2011-09-29

This is correct.

You have set the Fractional_Reserve on the volume to 20%

20% of a 800G LUN is 168G, which is then reserved in the volume space for snapshots of this LUN.

If you do not need to snapshot the LUN, you can set the Fractional_Reserve on the volume to 0% and this will "free" the reserved space as well.

Peter

chinchillaking · ‎2011-09-29

Hi Peter,

You are right. But, I don't understand why "Fractional_Reserve" don't free up space when I delete all snapshot?

Best regards,

Chung

peter_lehmann · ‎2011-09-29

Whether you have any snapshot or none, the fractional reserve setting just sets some space aside, for the case that you want to create a snpashot.

It's like a LUN-SnapShot-Guarantee... Which in your case of 20% is not really a guarantee, more a promise

Peter

radek_kubka · ‎2011-09-29

I actually agree with Chung - I would expect no impact from fractional reserve if there are no snapshots in the volume.

I vaguely remember some earlier discussions on Community where a 'hidden' snapshot created by de-duplication process was causing something similar.