Multipathing Impact on Performance

Multipathing configuration has always played a part in storage performance, and most vendors now use some form of Round Robin multipathing in order to get full use out all paths available between the host and storage. However even when using "round robin" multipathing, VMware (and some other OS'es)…

#Tags: vmware, performance, queue depth

VMware Queue Depths and Conflicting Worlds

One of the more confusing storage-related settings in VMware is the "SchedNumReqOutstanding" setting. In versions up to and including ESX 5.1 this was a global setting for all LUNs. From 5.5 on it because a per-LUN setting controlled with the 'esxcli storage core device set --sched-num-req-outstanding'…

#Tags: vmware, performance, queue depth

XtremIO and VMware Path Failure Detection

In XtremIO XIOS version 4.0.10 we made an (optional) change to the SCSI error codes that the array returns to ESX hosts under certain circumstances. To understand the difference, we first need to understand a little about how VMware acts when a LUN disappears for some reason. When…

#Tags: xtremio, vmware, APD, PDL