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Help interpreting available space

Hi all,

Can pls help me interprete the available space?

n3300> aggr show_space -h
Aggregate 'aggr0'

    Total space    WAFL reserve    Snap reserve    Usable space       BSR NVLOG
         4138GB           413GB           186GB          3538GB             0KB

Space allocated to volumes in the aggregate

Volume                          Allocated            Used       Guarantee
vol0                                873GB           202GB          volume
vol2                                252GB           106GB          volume

Aggregate                       Allocated            Used           Avail
Total space                        1126GB           309GB          2615GB
Snap reserve                        186GB            40MB           186GB
WAFL reserve                        413GB            42MB           413GB

--------------

n3300> lun show
    /vol/vol0/qtvms1a/lun0        60g (64424509440)   (r/w, online, mapped)
    /vol/vol0/qtvms4a/lun0       180g (193273528320)  (r/w, online, mapped)
    /vol/vol0/qtvms5a/lun0        60g (64424509440)   (r/w, online, mapped)

---------------

n3300> df -h
Filesystem               total       used      avail capacity  Mounted on
/vol/vol0/               671GB      495GB      176GB      74%  /vol/vol0/
/vol/vol0/.snapshot        0KB     4324KB        0KB     ---%  /vol/vol0/.snapshot
/vol/vol2/               250GB      249GB      486MB     100%  /vol/vol2/
/vol/vol2/.snapshot        0MB        0MB        0MB     ---%  /vol/vol2/.snapshot

---------------

1. Aggr0 has total space of 3.5TB. Correct?

2. How much space is available in vol0? I think it should be around 600GB, but why the df -h command shows only around 176GB?

Thank you.

Re: Help interpreting available space

Well, some ideas

  • volume size != file system size. So you may have 873GB volume with only 671GB file system inside. Check with vol status -b
  • if lun reservation is enabled, LUN full size is accounted as used in df output but only physically written blocks are accounted in aggr show_space output. You apparently have 300GB of LUNs and something else on the same volume (almost 200GB), but LUNs are mostly empty

Re: Help interpreting available space

This is the lun status -b:

n3300> vol status -b
Volume              Block Size (bytes)  Vol Size (blocks)   FS Size (blocks)  
------              ------------------  ------------------  ----------------  
vol0                4096                176060424           176060424         
vol1                4096                471859200           471859200         
vol2                4096                65536000            65536000

Yes, lun reservation is enabled.

So, can I still create lun on vol0 for about 300GB? I'm not sure what "else" is 200GB.

Re: Help interpreting available space

Hi,

1. You have put LUNs in the same volume as the system files, vol0. It is NetApp best practice and industry standard to NOT mix vol0 with any LUNs or other way of serving

    data.

2. You could easily reclaim some space by turning snap reserve to 0 (zero) on your aggregate and having no snapshots at aggr. level. Unless you ever think you will overwrite your entire    

    aggregate there is no need for this space to be reserved. I d recommend turning snapshots off and having no snap reserve, but its your call. You might have the option to use it.

Regards,

Eric

Re: Help interpreting available space

He has volume of size 671G (as confirmed by vol status -b). How comes that aggr show_space shows that 873G are allocated for this volume? What consumes extra 202G? How is it related to either system volume or aggregate snap reserve?

Re: Help interpreting available space

Can you give us the "df -hr" output, which will show us the space used by the fractional reserve.

My guess is that the vol size shown by "df -h" + fractional reserve space  = volume allocation in "aggr show_space". Your "df -gA" will also show a used that will be less than total space allocated as shown in "aggr show_space". Why NetApp does it this way, I don't know

Re: Help interpreting available space

n3300> df -hr
Filesystem               total       used      avail   reserved  Mounted on
/vol/vol0/               671GB      590GB       81GB      199GB  /vol/vol0/
/vol/vol0/.snapshot        0KB     4324KB        0KB        0KB  /vol/vol0/.snapshot
/vol/vol1/              1800GB     1800GB        0GB        0GB  /vol/vol1/
/vol/vol1/.snapshot        0TB        0TB        0TB        0TB  /vol/vol1/.snapshot
/vol/vol2/               250GB      249GB      486MB        0MB  /vol/vol2/
/vol/vol2/.snapshot        0TB        0TB        0TB        0TB  /vol/vol2/.snapshot

n3300> df -gA
Aggregate                total       used      avail capacity 
aggr0                   3538GB      922GB     2615GB      26% 
aggr0/.snapshot          186GB        0GB      186GB       0% 
aggr1                   3538GB     1802GB     1736GB      51% 
aggr1/.snapshot          186GB       39GB      146GB      21%

Thanks for helping me. I'm really newbie here.

Re: Help interpreting available space

Hmm ... question: does NetApp reserve space immediately or only when snapshot is created? I remember having read something on this matter but forgot where.

If space is reserved immediately, df output makes sense. aggr show_space still not

OK, answering to myself. Quoting TR-3483: Data ONTAP removes or reserves this space from the volume as soon as the first Snapshot copy is created. There are some snapshots on vol0 (as indicated by snap reserve being != 0), which explains reservation.

Does not explain aggr show_space though

Message was edited by: aborzenkov

Re: Help interpreting available space

Nice, we found the missing 200 GB in the fractional reserve space. And yes, I also don't understand why NetApp did it this way

Assuming vol0 is the root volume, don't put LUNs in your root volume because it is not supported.

Re: Help interpreting available space

Ok, I've made mistake by using vol0 for LUN.

Can pls tell me the primary reason why I shouldn't do that?

Any remediation I can do about it? Maybe moving the LUN to other volume. Is it risky?

So, for this mistake, how much space I've wasted? Is it the 200GB?