Disk I/O to Sun ZFS 7120 via iSCSI is Slow
Last updated on MARCH 08, 2017
Applies to:Linux OS - Version: Oracle Linux 5.6 with Unbreakable Enterprise Kernel [2.6.32]
After various I/O performance tests (including vdbench benchmark tool) the average service time (svctm) is good (5-7 ms) but the await (average wait time for an I/O request) is very high (900 ms). All statistics are collected by iostat.
According the Linux man pages, the await is the average time (in milliseconds) for I/O requests issued to the device to be served. This includes the time spent by the requests in queue and the time spent servicing them.
The servers are connected via a 10Gb connection to the ZFS appliance running iSCSI.
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