Random I/O workload tuning

You can improve random I/O performance on your ZVOL device by using a smaller "Volume block size" parameter. 

Depending on the disk type used for your storage Pool, the smallest recommended values are as follows:

• for HDD-based Pools: 32 KiB
• for SSD-based Pools: 16 KiB

WARNING: remember to configure the Volume block size before starting the production. The changes affect only the data not yet written to the storage, meaning that data already stored will be unaffected.

The default Volume block size (64 KiB) is a compromise between random and sequential I/O performance. To achieve better random I/O, a smaller Volume block size should be used. 

However, this comes with a tradeoff: as ZFS generates an ~300-byte checksum for every block regardless of the configured size, smaller Volume block size produces more checksums. This creates a bigger overhead for data which might affect the overall available storage size.

Additional performance tuning tips

To further tune the performance of your ZVOL-based storage you can refer to the following steps:

• enable Multipath configuration on the client's side
  Enabling Multipath on the client's machine that utilizes multiple connections to the storage can improve the overall performance greatly by avoiding or minimizing network bottlenecks. An example of Multipath configuration for iSCSI protocol under Windows software can be found here: https://kb.open-e.com/jdss-dss-v7-how-to-connect-to-a-iscsi-target-with-mpio-using-microsoft-iscsi-initiator_3211.html
   
• iSCSI tuning for client machines
  Our product come with a set of pre-configured parameters for iSCSI target. Make sure the same values are applied on the client's side to ensure best possible stability and performance of connection. More details can be found here: https://kb.open-e.com/jdss-iscsi-target-tuning-settings-in-joviandss_3061.html