How a ZFS SLOG Improves Datto SIRIS Performance

Recently, we added an Intel® Optane™ SSD-based ZFS SLOG to Datto’s GEN 4 SIRIS Professional and Enterprise appliances and now partners can specify a SLOG device when building their own appliance with the Datto SIRIS Imager, as well. Datto is the first, if not only, channel vendor to add a flash-based ZFS SLOG to appliances.

Our testing showed that the ZFS SLOG storage system eliminated bottlenecks in virtualization performance and improved boot times for concurrent virtual machines (VMs) by up to 20x. Click here to learn more about the test conditions and results.

So what exactly is the ZFS SLOG?

ZFS utilizes what is known as the ZFS Intent Log (ZIL) for write operations. When ZFS receives a write request, it is cached in the ZIL before it is sent to the disk system. There’s a delay (typically about 5 seconds) from the time data is cached to when it’s written to disk. A write cache benefits performance, as all writes going to disk are better organized and more manageable for spinning disks to process.

Moving the ZIL onto separate high-speed Intel® Optane™ SSDs (ZFS SLOG or Separate Intent Log) delivers a considerable increase in write performance. This was evident in the SIRIS 3 vs. SIRIS 4 benchmark performance.

Our testing showed that:

• SIRIS 4 Enterprise gains 2000% to 7000% write improvement over SIRIS 3 Enterprise because SLOG offloads synchronous write away from the pool, and frees up resources for real application.
• SIRIS 4 Enterprise shows 20-30% read improvement over SIRIS 3 Enterprise. This result is reasonable as SLOG is a write buffer, so it doesn’t help reading speed directly.
• SIRIS 4 Enterprise is 71x times faster. SLOG improves overall system performance when the system has a mixed workload.

To learn more about BCDR virtualization performance improvements associated with SSD storage, schedule a SIRIS 4 demo.