Asustor AS7008T 8-bay Intel Haswell SMB NAS Review

Multi-Client iSCSI Evaluation

As virtualization becomes more and more popular even in home / power user settings, the importance of the iSCSI feature set of any COTS NAS can't be overstated. Starting with our ioSafe 1513+ review, we have started devoting a separate section (in the reviews of NAS units targeting SMBs and SMEs) to the evaluation of iSCSI performance. The Asustor ADM only allows for iSCSI LUNs to be created as regular files and doesn't allow for multiple sessions to a single target. Even the Seagate NAS Pro units have this capability. Fortunately, from a review perspective, we only had one iSCSI configuration to evaluate.

We evaluated the performance of the Asustor AS7008T with file-based LUNs only. The standard IOMeter benchmarks that we used for multi-client CIFS evaluation were utilized for iSCSI evaluation also. The main difference to note is that the CIFS evaluation was performed on a mounted network share, while the iSCSI evaluation was done on a 'clean physical disk' (from the viewpoint of the virtual machine).

Performance Numbers

The four IOMeter traces were run on the physical disk manifested by mapping the iSCSI target on each VM. The benchmarking started with one VM accessing the NAS. The number of VMs simultaneously playing out the trace was incremented one by one till we had all 25 VMs in the fray. Detailed listings of the IOMeter benchmark numbers (including IOPS and maximum response times) for each configuration are linked below:

• Asustor AS7008T - 8 HDDs / RAID-5 / 2x 1G - LUNs (Regular Files)

Asustor AS7008T - LUNs (Regular Files) - 100% Sequential ReadsSynology DS1815+ - LUNs (Regular Files) - 100% Sequential ReadsSynology DS1815+ - Single LUN on RAID - 100% Sequential ReadsSynology DS1815+ - Multiple LUNs on RAID - 100% Sequential Reads

Asustor AS7008T - LUNs (Regular Files) - Max Throughput - 50% ReadsSynology DS1815+ - LUNs (Regular Files) - Max Throughput - 50% ReadsSynology DS1815+ - Single LUN on RAID - Max Throughput - 50% ReadsSynology DS1815+ - Multiple LUNs on RAID - Max Throughput - 50% Reads

Asustor AS7008T - LUNs (Regular Files) - Random 8K - 70% ReadsSynology DS1815+ - LUNs (Regular Files) - Random 8K - 70% ReadsSynology DS1815+ - Single LUN on RAID - Random 8K - 70% ReadsSynology DS1815+ - Multiple LUNs on RAID - Random 8K - 70% Reads

Asustor AS7008T - LUNs (Regular Files) - Real Life - 65% ReadsSynology DS1815+ - LUNs (Regular Files) - Real Life - 65% ReadsSynology DS1815+ - Single LUN on RAID - Real Life - 65% ReadsSynology DS1815+ - Multiple LUNs on RAID - Real Life - 65% Reads

Synology provides multiple ways to create iSCSI LUNs, each with different pros and cons (we are only looking at the bandwidth and response time numbers in the graphs above). The problem for the AS7008T lies in the fact that there are only two network links. This severely hampers the benchmark numbers and causes performance to degrade beyond a couple of clients for the real life 60% random / 65% reads workload. The other traces have the same behaviour as the multi-client CIFS workloads, but Synology just provides more alternatives to the end-user.