Storage Magazine - UK

Overland Storage SnapServer DX2

From STORAGE Magazine Vol 12, Issue 02 - July 2012


The latest SnapServer DX-series of NAS appliances aim to take the strain out of provisioning network storage by automating the entire process. A key feature of Overland's new GuardianOS 7 is DynamicRAID, which allows you to mix and match hard disks of different capacities and makes in the same array.

The drives are placed in a central storage pool, and you can choose single or dual parity during its creation. Don't worry if you change your mind afterwards, as you can swap between each one on the fly.

Capacity expansion is simple, as you just add more drives to the pool as required and existing drives can also be swapped out for larger ones, without incurring any downtime. There's room to expand outside the box, as the SnapServer DX2 on review supports up to seven SnapExpansion disk shelves, allowing total capacity to be increased to 288TB.

Thin provisioning is implemented on NAS volumes, which are created within the storage pool and grow or shrink in size automatically as demand dictates. If you wish, you can place quotas on selected NAS volumes to limit their maximum size.

Deployment is swift, as the SnapServer Manager (SSM) discovers the appliance on the network and provides quick access to its well designed web interface. A wizard guides you through initial setup, which includes DynamicRAID configuration where you choose single or dual parity and decide how much space to keep aside for snapshots.

NAS volumes can have point-in-time snapshots assigned to them. The impact of backup operations can be reduced, as a NAS share presents its own snapshot as a separate public or private share that can be used as a backup source.

The CIFS/SMB, AFP, NFS and FTP protocols are all supported, allowing Windows, Linux, Unix and Mac clients to access the appliance. Each protocol can be enabled or disabled individually for each network share, and access restrictions applied using the local user database or AD domain authentication.

Overland's Snap EDR (enterprise data replicator) software increases value, as this allows selected shares to be synchronised with other systems. You can distribute files from one source to multiple locations, aggregate files from multiple sources to a single location, and replicate files and folders between one source and one target. Overland offers optional agents for Windows and Linux systems, allowing them to be included in the replication tasks.

IP SAN support is a standard feature and the appliance supports up to 256 virtual volumes. Target creation is simple, as you take space from the storage pool, enter a capacity for the target and activate CHAP authentication, if required.

Full support for Microsoft's Volume Shadow Copy Service (VSS) and the Virtual Disk Service (VDS) means snapshots may be taken of iSCSI targets. These use VSS compatible backup software on the hosts, allowing application consistent snapshots to be taken without any downtime.

The SnapServer DX2 delivered excellent results in our lab performance tests. Copies of a large video clip to and from a NAS share over Gigabit returned high read and write rates of 107.5MB/sec, which increased to 109MB/sec over FTP.

Overland claims a top throughput of 350MB/sec for the DX2 and we found this is quite achievable. Using four Windows Server 2008 R2 hosts, connected to dedicated iSCSI targets and network ports, we saw the open source Iometer report a cumulative raw read throughput of over 400MB/sec.

Along with top performance, the SnapServer DX2 looks excellent value, as all features are included as standard and not as optional extras. Expansion potential and data protection features are very good and Overland's new DynamicRAID really does make light work of storage provisioning.

Product: SnapServer DX2
Supplier: Overland Storage
Tel: 0118 989 8000
Web site:
Price: 8TB (4 x 2TB Enterprise drives) - £3,999

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