NetApp ONTAP working with Snapshots

Note: The areas described in the article were tested in version ONTAP 9.15.1P8. The article primarily focuses on SAN Volumes and Snapshots on them.

In the article Veeam Backup & Replication - Snapshot-Only Job and Recovery from Storage Snapshot we dealt with Snapshot orchestration and recovery from the Veeam side. We also covered some concepts and principles. Here we will look at working with Snapshots directly on storage with the NetApp ONTAP system. For data recovery we have various options, but all steps must be performed manually.

NetApp Snapshots Technology

NetApp was one of the first companies (possibly the very first) to introduce the feature of efficient Storage Snapshots. The key advantage of NetApp Snapshots is that they have no performance impact and are highly scalable. They efficiently utilize storage because they only occupy space for changed data blocks.

Snapshots can be used for both NAS volumes (file access - NFS export, SMB/CIFS share) and SAN volumes (block access - LUN), as well as for S3 buckets.

ONTAP Snapshots

• Learn about managing local ONTAP snapshots

Snapshot refers to instant capture of system or data state at a specific time. NetApp describes a Snapshot as a read-only image of a volume at a specific point in time. No data copying or duplication occurs. Snapshots do not replace backup.

WAFL and pointers

NetApp uses its WAFL (Write Anywhere File Layout) technology to create low-overhead Snapshots, which it refers to as Snapshot Copies. WAFL uses pointers to data blocks on disk. When writing, it does not overwrite existing blocks, but writes (updated) data to new (free) blocks and changes the pointers.

A Snapshot contains only pointers that were in the volume at the time the Snapshot was taken (blocks contained in the Snapshot are locked and are not deleted or overwritten when original data is deleted). Creating a snapshot is almost instantaneous, takes up little space (only deleted or changed data blocks since its creation) and does not burden the system (does not slow it down).

Volume Snapshot

Snapshots are created at the FlexVol volume (Flexible Volume) level. They are stored in the volume from which they were taken (occupying its space). Since ONTAP 9.4, we can create up to 1023 for one volume. Above FlexVol is the protocol layer (NFS, SMB/CIFS, FC/FCoE/iSCSI).

Snapshots can be created manually or automatically using a scheduler. Automatic Snapshot deletion is usually used, which removes Snapshots that have reached a certain age. Snapshots can also be replicated to another NetApp system, which may be in a different geographical location.

Data consistency in Snapshot

When we perform a SAN volume Snapshot, it is Crash-consistent. If we want to have a Snapshot in a consistent state, we must use some application with client integration. This could be NetApp SnapCenter or Veeam Backup & Replication for VMware.

NetApp FlexClone

• FlexClone volume use overview
• Clone volumes and LUNs for testing

FlexClone, also referred to as a virtual copy, is a Snapshot with write capability. It allows instant creation of a writable copy of a volume that shares data blocks with the parent. It is used for testing, development, analysis, or recovery without affecting production data.

We can clone a FlexVol volume (a Snapshot is created or an existing one is used) or a specific Snapshot which creates a FlexClone volume. Each FlexClone can be further cloned. A FlexClone volume can be separated from its parent volume at any time using the Split function.

Note: FlexClone technology can also be used for file cloning in NAS environments or LUN cloning in SAN environments.

NetApp tools and features

NetApp offers additional tools for working with Snapshots, such as

• SnapCenter - centralized backup management, integration with applications (e.g. Exchange, SQL)
• SnapMirror - data replication between two NetApp systems
• SnapRestore - enables quick recovery of entire volumes or individual files from Snapshots
• SnapVault - long-term data backup using snapshot replication to secondary storage
• SnapLock - ensuring data immutability (Immutability / WORM)

Using Snapshots for data recovery

• recovery of specific files - within NAS volumes we can easily restore deleted or corrupted files from specific Snapshots, these are available in the .snapshot directory in the given Share (if enabled, it is available to users)
• recovery of entire volume (Volume Restore) - restoration (rollback) of entire volume to Snapshot state, overwrites current volume data and is irreversible, existing Snapshots remain
• FlexClone of Snapshot - cloning creates a volume that we can mount to a server and copy data from

Working with Snapshots in NetApp ONTAP

In newer versions of the ONTAP system, we can manage Snapshots through both CLI (Command Line Interface) and GUI (Graphical User Interface) System Manager.

Manual creation and deletion of Snapshots

A Snapshot can be very easily and quickly created at the current time. Similarly, we can delete an existing Snapshot without affecting the volume or other Snapshots.

ONTAP System Manager

• ONTAP System Manager
• Storage - Volumes - click on the desired volume
• switch to the Snapshot copies tab
• creating a Snapshot
  • click on Add
  • enter a name and click Add

• deleting a Snapshot
  • for the selected Snapshot, click on the three dots on the right and choose Delete
  • check Delete snapshot copy and confirm Delete

ONTAP CLI

• volume snapshot create

volume snapshot create -vserver <vserver_name> -volume <volume_name> -snapshot <snapshot_name>
volume snapshot delete -vserver <vserver_name> -volume <volume_name> -snapshot <snapshot_name>

Snapshot reserve

On a volume we can set a percentage reservation for Snapshots. The space available for data is reduced by this amount. This part of the volume capacity is reserved for storing changes caused by Snapshots. It is part of the volume itself, data and Snapshots are stored in the active file system.

Note: If the snapshot reserve is not sufficient, Snapshots will begin to consume regular data space. The volume may become full. We also have the option to enable automatic deletion of Snapshots when the Snapshot reserve is exceeded.

• ONTAP System Manager
• Storage - Volumes - for the selected volume, click on the three dots on the right and choose Edit - Volume
• at the bottom is the Snapshot copies (local) settings section
• under Snapshot reserve % enter the percentage value of the reserve, information will be displayed showing how much space this represents

Snapshot policies and Snapshot scheduling

Snapshot Policies determine when snapshots should be created, how many copies should be retained, and how they should be named. To determine when Snapshots should be created, a Snapshot Job Schedule is used. We can combine almost any variants, such as regular hourly, daily, weekly, but also various special ones. Basic configurations are prepared in advance.

When creating or editing a volume, we can enable scheduling of Snapshot creation (Schedule Snapshot copies) and select a prepared policy. According to the schedule, Snapshots will be automatically created and old ones deleted (after reaching the specified number).

ONTAP System Manager

Schedule management

• ONTAP System Manager
• Protection - Overview - find and expand the Local policy settings section
• click on the arrow next to the Schedules panel

Snapshot policies management

• ONTAP System Manager
• Protection - Overview - find and expand the Local policy settings section
• click on the arrow next to the Snapshot policies panel

Setting policy on volume

• ONTAP System Manager
• Storage - Volumes - for the selected volume, click on the three dots on the right and choose Edit - Volume
• at the bottom is the Snapshot copies (local) settings section
• check Schedule Snapshot copies and select Snapshot Policy

ONTAP CLI

job schedule cron create ... 
volume snapshot policy create ... 
volume create ...
volume modify ...

Information about Snapshots and their size

We can see the list of Snapshots for a specific volume. It is easy to find out how much capacity all Snapshots occupy in total within a given volume. More complex is obtaining a detailed overview of the size of individual Snapshots. To obtain this, it is often necessary to use the command line (CLI). Through CLI you can display details such as Snapshot size, differential data (delta) or volume that can be freed (reclaimable).

ONTAP System Manager

• ONTAP System Manager
• Storage - Volumes - click on the desired volume
• Snapshot list
  • switch to the Snapshot copies tab
• occupied space
  • on the Overview tab we see the Capacity panel
  • we see information about the volume, occupied space, reserve for Snapshots
  • we can click in the upper part and a more detailed overview will be displayed

ONTAP CLI

Information about volume utilization. We can see how much Snapshots occupy.

AFF::> df -volume VMware_vol_02

Filesystem                       kbytes         used      avail capacity  Mounted on  Vserver
/vol/VMware_vol_02/         12777527708  11627695260 1149832448      91%  ---         svm-iscsi
/vol/VMware_vol_02/.snapshot 2254857828   1057566280 1197291548      47%  ---         svm-iscsi
2 entries were displayed.

How much free space is in the reservation for Snapshots.

AFF::> volume show -volume VMware_vol_02 -fields snapshot-reserve-available

vserver   volume        snapshot-reserve-available
--------- ------------- --------------------------
svm-iscsi VMware_vol_02 1.10TB

List of Snapshots for a given volume and their size.

AFF::> volume snapshot show -volume VMware_vol_02
                                                                 ---Blocks---
Vserver  Volume   Snapshot                                  Size Total% Used%
-------- -------- ------------------------------------- -------- ------ -----
svm-iscsi
         VMware_vol_02
                  VeeamSourceSnapshot.2025-05-23_1600    43.24GB     0%    0%
                  VeeamSourceSnapshot.2025-05-24_0000    71.50GB     0%    1%
                  VeeamSourceSnapshot.2025-05-24_0800    186.9GB     1%    2%
                  VeeamSourceSnapshot.2025-05-24_1600    60.24GB     0%    1%
                  VeeamSourceSnapshot.2025-05-25_0000    69.09GB     0%    1%
                  VeeamSourceSnapshot.2025-05-25_0800     1.18GB     0%    0%
6 entries were displayed.

What space will be freed if we delete one or more Snapshots. The command performs a calculation. The value may be smaller than the Snapshot size. Some blocks may be shared by multiple Snapshots, so they are not deleted when one Snapshot is deleted.

AFF::> volume snapshot compute-reclaimable -vserver svm-iscsi -volume VMware_vol_02 -snapshots VeeamSourceSnapshot.2025-05-23_1600

A total of 1961984 bytes can be reclaimed.

Information about the difference (number of bytes that have changed) between two Snapshots or a Snapshot and the active system.

AFF::> volume snapshot show-delta -vserver svm-iscsi -volume VMware_vol_02 -snapshot1 VeeamSourceSnapshot.2025-05-23_1600 -snapshot2 VeeamSourceSnapshot.2025-05-25_0800

A total of 455055507456 bytes (111097536 blocks) are different. Elapsed time between the Snapshot copies: 1d 15h 59m 55s.

Data recovery from Snapshot

File recovery in NAS environment is simple and described in the documentation Restore files from Snapshot. Here we will look at recovery within SAN.

Volume recovery from Snapshot

Rolling back the volume to the Snapshot state. This step overwrites the current volume data and is irreversible.

ONTAP System Manager

• ONTAP System Manager
• Storage - Volumes - click on the desired volume
• switch to the Snapshot copies tab
• for the selected Snapshot, click on the three dots on the right and choose Restore

ONTAP CLI

volume snapshot restore -vserver <vserver_name> -volume <volume_name> -snapshot <snapshot_name>

Volume cloning using FlexClone

From a Snapshot we can create a clone that functions as a standard volume (the LUN is also cloned). We can mount it to a server and access the data on it. This could be for example a VMware ESXi server, where it is possible to register VMs from the Snapshot and recover data inside the VM.

Note: We can create a FlexClone directly from a volume, but a Snapshot is automatically created and used.

Step-by-step procedure for VMware connection

• on the array we create a Snapshot clone
• on the array we map the LUN to hosts (Map to initiator group)
• on the ESXi server we perform Rescan HBA
• on the ESXi server we add a Datastore (Storage - New Datastore), to which we connect the VMFS volume with a new signature (Resignature unresolved VMFS volume)

ONTAP System Manager

• ONTAP System Manager
• Storage - Volumes - click on the desired volume
• switch to the Snapshot copies tab
• for the selected Snapshot, click on the three dots on the right and choose Clone volume
• enter a name and click Clone

In the volume list we can see the created clone and work with it in the standard way.

ONTAP CLI

volume clone create -vserver <vserver_name> -flexclone <clone_name> -parent-volume <source_volume> -parent-snapshot <snapshot_name>