Is there a way to clean large aggregate footprint

[nicolasbegard]

Hello,

We encounter a strange issue on 8.2.4 7 mode.

An aggregate is filled with more than 3 TB of datas,

Aggregate               kbytes       used      avail capacity  
aggr0               21055590144 3609363136 17446227008      17%  
aggr0/.snapshot              0          0          0       0%

and however there are only 2 volumes in that aggregate of around 250 Go:

Filesystem              kbytes       used      avail capacity  Mounted on
/vol/volboot/        249036800    6923172  242113628       3%  /vol/volboot/
/vol/volboot/.snapshot   13107200     112104   12995096       1%  /vol/volboot/.snapshot
/vol/volpraboot/     249036800    4945480  244091320       2%  /vol/volpraboot/
/vol/volpraboot/.snapshot   13107200      31516   13075684       0%  /vol/volpraboot/.snapshot

 We can see that this amount of space is consumed of footprint:

Aggregate : aggr0

      Feature                                           Used      Used%
      --------------------------------      ----------------      -----
      Volume Footprints                               3.36TB        17%
      Aggregate Metadata                              1.85MB         0%

      Total Used                                      3.36TB        17%

For information, this aggregate was build with disks from a new shelf, then vol boot was moved into that new shelf (ndmpcopy), filer restarted, and then original aggr0 was deleted.

Should the volume footprints of aggr0 be the sum of each volume footprint ? It doesn't seem to be the case as individual volume foot print do not represent 3 TB

Is there a way to reduce the size of these footprint ?

Many thanks for your help,

Regards

[sgrant]

Hello,

The volume footprint will include the volume size as well as any metadata. From  Storage Management Guide: https://library.netapp.com/ecmdocs/ECMP1368859/html/GUID-77834FDB-81FE-4FD2-BB0F-3DF9390F3197.html

However, 3TB does sound excessive for metadata. Your DF output will however only show online volumes. While it sounds like this is a new aggregate, do you have any other volumes not online that could account for the difference?

Thanks,

Grant.

[nicolasbegard]

Hi Grant,

Thanks for your feedback.

I checked but no: no offline volume present.

Although no snap of any kind.

Regards,

[sgrant]

If you could supply the output of the following commands we should see the offending volume:

vol status -S

vol status -F

Let me know.

Thanks,

Grant.

[nicolasbegard]

Thanks a lot Grant for pointing me to a good thing, here is the output:

vol status -S

Volume : volboot

      Feature                                           Used      Used%
      --------------------------------      ----------------      -----
      User Data                                       6.58GB         3%
      Filesystem Metadata                             2.51MB         0%
      Inodes                                          3.23MB         0%
      Snapshot Reserve                                12.5GB         5%

      Total                                           19.0GB         8%


Volume : volpraboot

      Feature                                           Used      Used%
      --------------------------------      ----------------      -----
      User Data                                       4.66GB         2%
      Filesystem Metadata                             2.17MB         0%
      Inodes                                          3.71MB         0%
      Snapshot Reserve                                12.5GB         5%

      Total                                           17.1GB         7%

and vol status -F

Volume : volboot

      Feature                                           Used      Used%
      --------------------------------      ----------------      -----
      Volume Data Footprint                           2.66GB         0%
      Volume Guarantee                                 244GB         1%
      Flexible Volume Metadata                        1.38GB         0%
      Delayed Frees                                   2.42GB         0%

      Total                                            251GB         1%


Volume : volpraboot

      Feature                                           Used      Used%
      --------------------------------      ----------------      -----
      Volume Data Footprint                            704MB         0%
      Volume Guarantee                                3.09TB        16%
      Flexible Volume Metadata                        17.6GB         0%

      Total                                           3.11TB        16%

There is a guarantee fixed on volpraboot, which is a snapmirror target. I'll do some tests and let you know.

Many thanks! 

[sgrant · Accepted solution]

Yep, some SnapMirror destination volumes are deliberatly created large to avoid the issue when the source volume is autosized. Unless the SnapMirror is broken and the fs_size_fixed option is turned off it will not actually consume this space.

[nicolasbegard]

Hi Grant,

Many thanks for your help, we'll review this relation.

Regards