NAS NDMP Backup Challenges
Enterprise storage has witnessed unprecedented growth of unstructured data over the last decade. This has created multiple challenges for implementing efficient backup and recovery policies.
The Dell EqualLogic FS7500 NAS supports standard backup software using NDMP Ver 4.0. With no optimizations, the NDMP backup processes uses one network interface on the backup server and the maximum backup throughput is limited to 120 MB/sec (this is the theoretical max of a 1 Gb NIC). This limitation is not acceptable when the amount of data stored on the NAS grows because storage administrators will not be able to meet aggressive RTO and RPO requirements.
Note: The theoretical limit of 120 MB/sec does not apply to FS7610 platform which uses 10 Gig interfaces.
FluidFS architecture & CommVault features to address the NDMP backup challenge
The Dell FS7500 NAS is capable of providing near line rates for large file backups. To achieve higher optimized backup throughput, we need to use multiple front-end NICs on an FS7500 and also multiple NICs on the backup server. FluidFS architecture allows up to eight Virtual IP addresses to be defined per NAS appliance and network load is automatically balanced across all these interfaces. These virtual IP addresses can be used to address the NAS independently. In a backup context, this allows creation of independent backup paths to the NAS, thereby allowing the FluidFS firmware to dedicate exclusive resources to independent backup paths.
The CommVault feature ‘Data interface pairs’ allows you to create pairs of network interfaces. Each pair consists of a single interface on the backup server and a single Virtual IP (VIP) on the NAS. The unique source-destination addresses of the data interface pair enable the backup process to take advantage of multiple NICs and other resources on the NAS.
The following diagram shows how the FluidFS network load balancing feature was used along with the CommVault data interface pairs feature to optimize NDMP backup.
Note: A Dell DL2200 with CommVault Simpana was used as the NDMP client in the test configuration. The same principles can be applied to other backup applications such as Symantec, as long as similar features are supported.
Configuration steps
Steps to achieve higher backup throughput using Dell FluidFS network load balancing and the CommVault ‘Data Interface Pairs” feature are listed below.
- Four virtual IP addresses were defined on the FS7500 as shown in the figure below.
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Note: Theoretically, the data interface pairs can be created using all eight VIPs that map to eight client network interfaces of the FS appliance, but the test setup used only four NICs.
- Assign and dedicate four NICs on the backup server with separate IP addresses.
- Create a mapping between four individual virtual IP addresses on the FS7500 with the four dedicated IP addresses configured on the backup server. This pairing was created using the CommVault CommCell console.
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As shown in the above diagram, four virtual IP addresses on the FS7500 were added as 1st Machine Interfaces. Similarly, four IP addresses on the backup server were added as 2nd Machine Interfaces.
Performance Benefits
The Data Interface Pairs feature from CommVault was used to distribute the network throughput across all four NICs dedicated for client connectivity. This optimization along with the FluidFS network load balancing feature enabled utilization of all four NICs on the backup server and four client facing NICs on the FS7500. This effectively created four 1 G lanes for backup and improved the backup performance by approximately 135%. In my test setup, only three EqualLogic PS6100XV arrays were used as back end storage for the FS7500 appliance. Additional arrays would have helped in scaling the backup performance further.
