Most customers back up their data after business hours because the backup operation does not compete with the user activity from performance sensitive protocols like SMB and NFS. NDMP backup and restore performance depends on many factors, such as the NDMP backup models, network bandwidth, DMA configuration, available system resources, directory depth, number of files per directory, and file size.
The following considerations and best practices can help you optimize OneFS NDMP backup and restore operations.
- Install the latest roll up patches (RUP) for OneFS and DMA. We strongly recommend installing OneFS 8.2.2 GA RUP 2021-09 or later Patch and OneFS 9.1.0.14+ when using OneFS NDMP.
- Run a maximum of eight NDMP concurrent sessions for each Fibre attached storage node. Run four NDMP concurrent sessions for each PowerScale backup accelerator node to obtain optimal throughput in each session.
- Isolate NDMP backup sessions from other workloads such as SMB or NFS user activity.
- For NDMP two-way backups, the B100 backup accelerator requires OneFS 9.3.0.0 or later.
- Assign static IP addresses to Fibre Attached Storage nodes. Attach more Fibre Attached Storage nodes to larger PowerScale clusters or if you are backing up to more tape devices. The following table shows the recommend number of PowerScale nodes for each Fibre attached storage node.
Table 4. Recommended PowerScale nodes for each Fibre attached storage node
F-Series | 3 |
H-Series | 3 |
A-Series | 3 |
X-Series | 3 |
NL-Series | 3 |
S-Series | 3 |
HD-Series | 3 |
- NDMP backups result in high Recovery Point Objectives (RPOs) and Recovery Time Objectives (RTOs). You can attach one or more Fibre Attached Storage nodes to the PowerScale cluster before running NDMP two-way sessions and reduce the RPO and RTO.
- NDMP backup and restore performance depends on the file size. The performance is considerably reduced for small files. If you are backing up large numbers of small files, set up a separate schedule for each directory.
- If you restore files to another PowerScale cluster using NDMP, we recommend having the same OneFS and patch version installed on the source and target clusters.
- If you are performing NDMP three-way backups, run multiple NDMP sessions on multiple nodes in the PowerScale cluster.
- For NDMP three-way backups, configure using dedicated switch ports for all NDMP PowerScale nodes.
- Use Dell PowerScale SmartPools and file pool policies to move data to a node pool for NDMP backups.
- With NDMP, compressed chunks are decompressed. Each file is then reassembled and sent over Fibre Channel (2-way NDMP) or Ethernet (3-way NDMP) in uncompressed form to the backup devices.
- With NDMP, deduplicated data is rehydrated when it leaves the cluster, and shadow stores and shadow links are not preserved on the backup. The NDMP tape device or VTL will need to have sufficient space to house the full size of the dataset. When NDMP backs up deduplicated data, the NDMP performance will be impacted.
- Recover files through DDAR if you recover large numbers of files frequently.
- Use the largest tape block size available for OneFS to increase NDMP backup and restore throughput.
- If possible, do not include or exclude files from NDMP backups. Including or excluding files can affect backup performance, due to filtering overhead.
- Limit the depth of nested subdirectories in the OneFS file system for NDMP backups.
- Enable parallelism on DMA to enable multi-stream backup if DMA supports this option, and ensure that there are enough tape devices to support the multi-stream backup. This feature allows OneFS NDMP to back up data to multiple tape devices simultaneously and improves the backup performance. We recommend starting with two streams for the multi-stream backup. If there are too many attempts, multiple NDMP jobs lock onto the same snapshot. This causes locking contention.
- All PowerScale nodes support NDMP. Considering that the archive nodes have fewer CPU resources, we recommend against running NDMP jobs on archive nodes which can impact other workloads such as SMB or NFS user activity.
- Backing up /ifs is not a supported configuration.
- The maximum number of client sessions is 3,000 per node. If the number of client sessions exceeds 3000, it can result in degraded performance.
- NDMP MSBRE is not supported in releases prior to OneFS 9.1.0.0.
- Consider the following NDMP limitations when using NDMP backups.
- NDMP supports block sizes up to 512 KB. We recommend setting it to a maximum of 256 KB.
- NDMP does not support more than 4 KB file path length.
- NDMP operates best with a directory depth at 15 or fewer directories.
- NDMP does not back up OneFS configuration data, such as file protection level policies and quotas.
- NDMP does not support recovering data from a file system other than OneFS.
- Fibre Attached Storage nodes cannot interact with more than 4096 tape paths.
- The maximum length of the FILESYSTEM NDMP environment variable supported for a backup operations is 1024.
