Dell PowerEdge RAID Controller 12 User’s Guide PERC H965i Adapter, PERC H965i Front, PERC H965i MX, and PERC H965e Adapter

Single virtual disk performance or latency in hypervisor configurations

Multi-initiator or hypervisor configurations running multiple I/O workloads to a single RAID array may experience degraded performance or latency. This is caused by upper layers sending separate I/O workloads for each virtual machine to the storage subsystem which ends up being a random I/O workload to the underlying RAID array. For I/O workload configurations that require lower latency restrictions and higher I/O performance it may be beneficial to run fewer I/O workloads to individual RAID arrays or to use separate RAID arrays and physical disks for each I/O workload. Other considerations are making sure write-back cache is enabled for rotational disks or using solid state drives (SSDs) to improve random I/O workload performance.

Performance degradation may also be observed when background operations such as initialization, consistency check, or rebuilds are running on the virtual disk. See your hypervisor storage best practices or performance best practices guides for additional configuration support.