The transition to NetApp MS Azure AD B2C is complete. If you missed the pre-registration, you will be invited to reigister at next log in.
Please note that access to your NetApp data may take up to 1 hour.
To learn more, read the FAQ and watch the video.
Need assistance? Complete this form and select “Registration Issue” as the Feedback Category.

ONTAP Discussions

Can't shrink a volume that is 7 TB bigger than the LUN that's on it

wsanderstii

We have come up against the 16TB size lmit for a LUN in Ontap 8.3.1. The LUN is on a volume that has been grown to 23.04 TB, yet the LUN is only 16 TB. There are no other LUNs on the volume, yet the vol is 100% full. What is using this extra space on the volume? What is "Reserved Space for Overwrites" and why is it 6.45TB?

 

There are no snapshots on the volume and a 5% snapshot reserve.

 

How can we reclaim this 7+TB of space on the volume?

 

lun show:

/vol/VMDK_01/VMDK_01            online  mapped   vmware    15.97TB

vol show:

VMDK_01 netapp_clr301_01_aggr1
    online RW 23.04TB 0B 100%

vol show detail:

netapp-clr301::> vol show -vserver netapp-iscsi301 -volume VMDK_01

                                   Vserver Name: netapp-iscsi301
                                    Volume Name: VMDK_01
                                 Aggregate Name: netapp_clr301_01_aggr1
                                    Volume Size: 23.04TB
                             Volume Data Set ID: 1100
                      Volume Master Data Set ID: 2147484748
                                   Volume State: online
                                    Volume Type: RW
                                   Volume Style: flex
                         Is Cluster-Mode Volume: true
                          Is Constituent Volume: false
                                  Export Policy: default
                                        User ID: 0
                                       Group ID: 0
                                 Security Style: unix
                               UNIX Permissions: ---rwxr-xr-x
                                  Junction Path: -
                           Junction Path Source: -
                                Junction Active: -
                         Junction Parent Volume: -
                                        Comment:
                                 Available Size: 0B
                                Filesystem Size: 23.04TB
                        Total User-Visible Size: 21.89TB
                                      Used Size: 21.89TB
                                Used Percentage: 100%
           Volume Nearly Full Threshold Percent: 95%
                  Volume Full Threshold Percent: 98%
           Maximum Autosize (for flexvols only): 30TB
(DEPRECATED)-Autosize Increment (for flexvols only): 1GB
                               Minimum Autosize: 23.04TB
             Autosize Grow Threshold Percentage: 98%
           Autosize Shrink Threshold Percentage: 50%
                                  Autosize Mode: off
           Autosize Enabled (for flexvols only): false
            Total Files (for user-visible data): 31876689
             Files Used (for user-visible data): 101
                          Space Guarantee Style: volume
                      Space Guarantee in Effect: true
              Snapshot Directory Access Enabled: true
             Space Reserved for Snapshot Copies: 5%
                          Snapshot Reserve Used: 0%
                                Snapshot Policy: none
                                  Creation Time: Fri May 20 14:22:19 2016
                                       Language: C.UTF-8
                                   Clone Volume: false
                                      Node name: netapp-clr301-01
                                  NVFAIL Option: on
                          Volume's NVFAIL State: false
        Force NVFAIL on MetroCluster Switchover: off
                      Is File System Size Fixed: false
                                  Extent Option: off
                  Reserved Space for Overwrites: 6.45TB
                             Fractional Reserve: 100%
              Primary Space Management Strategy: volume_grow
                       Read Reallocation Option: off
               Inconsistency in the File System: false
                   Is Volume Quiesced (On-Disk): false
                 Is Volume Quiesced (In-Memory): false
      Volume Contains Shared or Compressed Data: true
              Space Saved by Storage Efficiency: 660.4GB
         Percentage Saved by Storage Efficiency: 3%
                   Space Saved by Deduplication: 660.4GB
              Percentage Saved by Deduplication: 3%
                  Space Shared by Deduplication: 72.02GB
                     Space Saved by Compression: 0B
          Percentage Space Saved by Compression: 0%
            Volume Size Used by Snapshot Copies: 0B
                                     Block Type: 64-bit
                               Is Volume Moving: false
                 Flash Pool Caching Eligibility: read-write
  Flash Pool Write Caching Ineligibility Reason: -
                     Managed By Storage Service: -
Create Namespace Mirror Constituents For SnapDiff Use: -
                        Constituent Volume Role: -
                          QoS Policy Group Name: -
                            Caching Policy Name: -
                Is Volume Move in Cutover Phase: false
        Number of Snapshot Copies in the Volume: 0
VBN_BAD may be present in the active filesystem: false
                Is Volume on a hybrid aggregate: false
                       Total Physical Used Size: 5.87TB
                       Physical Used Percentage: 25%

  

1 ACCEPTED SOLUTION

aborzenkov

@wsanderstii wrote:

There are no snapshots on the volume  


You have deduplication enabled and deduplication internally works with snapshots


@wsanderstii wrote:
netapp-clr301::> vol show -vserver netapp-iscsi301 -volume VMDK_01
...
Reserved Space for Overwrites: 6.45TB Fractional Reserve: 100%
...

  


Set fractional reserve to 0, this should free reserved space. Please note, this may result in out of space condition during writes to LUN.

View solution in original post

4 REPLIES 4

aborzenkov

@wsanderstii wrote:

There are no snapshots on the volume  


You have deduplication enabled and deduplication internally works with snapshots


@wsanderstii wrote:
netapp-clr301::> vol show -vserver netapp-iscsi301 -volume VMDK_01
...
Reserved Space for Overwrites: 6.45TB Fractional Reserve: 100%
...

  


Set fractional reserve to 0, this should free reserved space. Please note, this may result in out of space condition during writes to LUN.

View solution in original post

wsanderstii

Yes, after setting factional reserve to 0 the space was immediately freed up. I guess after working with netapps for 20+ years I still don't understand factional reserve. Perhaps no one does 🙂

 

The unanswered question is why the factional reserve claimed 23+ TB for the volume when it only has one LUN on it, reservation is *on* for the LUN, so the vol should only need 16TB for the LUN plus some space (6+ TB?!?) for metadata and deduplication. (The LUN is 99% full but reservation should make that irrelevant.) "vol show-footprint" and "vol show-space" didn't hint at that. 

 

I am still mystified why "show footprint" showed this

 

netapp-clr301::> vol show-footprint -volume VMDK_01

      Vserver : netapp-iscsi301
      Volume  : VMDK_01

      Feature                                   Used    Used%
      --------------------------------    ----------    -----
      Volume Data Footprint                   5.88TB      10%
      Volume Guarantee                       16.93TB      30%
      Flexible Volume Metadata               131.1GB       0%
      Deduplication                              8KB       0%
      Delayed Frees                          235.9GB       0%

      Total Footprint                        23.17TB      41%

when the 99% full 16TB LUN on the volume, with reservation on, is the only thing on the volume. 

aborzenkov

@wsanderstii wrote:

I guess after working with netapps for 20+ years I still don't understand factional reserve. Perhaps no one does 🙂


LUN space management (including fractional reserve) is described pretty extensively in TR-3483. I am surpsised you never came around to reading it in 20+ years. If I am mistaken and you did - do you have specific question about content of this TR?

wsanderstii

Thanks- that was a failed attempt at humor. I can say I don't recall ever deliberately turning fractional reserve on on ever. There are only a few use cases in TR-3483 where its use is mentioned.

Announcements
NetApp on Discord Image

We're on Discord, are you?

Live Chat, Watch Parties, and More!

Explore Banner

Meet Explore, NetApp’s digital sales platform

Engage digitally throughout the sales process, from product discovery to configuration, and handle all your post-purchase needs.

NetApp Insights to Action
I2A Banner
Public