Nexenta includes an option to enable or disable Write Back Cache on shared ZVols. To manage this setting, you must first create your ZVol and then set the ZVol to Shared. Then you can select the ZVol and edit the Write Back Caching setting. The purpose of this article is to find out how much performance is affected by the setting. All benchmarks were run on the ZFSBuild2012 hardware using Nexenta 3.1.3. All tests were run on the same ZFS storage pool. Click here to read about benchmark methods.
iSCSI-WC-E is iSCSI using IPoIB with connected mode disabled and the Write Back Cache enabled.
iSCSI-WC-D is iSCSI using IPoIB with connected mode disabled and the Write Back Cache disabled.
IB-SRP-WC-E is InfiniBand SRP with the Write Back Cache enabled.
IB-SRP-WC-D is InfiniBand SRP with the Write Back Cache disabled.
Generally speaking, enabling the Write Back Cache has no significant impact on read performance, but a huge improvement for write performance.
IOMeter 4k Benchmarks:
IOMeter 8k Benchmarks:
IOMeter 16k Benchmarks:
IOMeter 32k Benchmarks:
13 Comments to ZFSBuild2012 – Write Back Cache Performance
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