Parsing XtremIO CLI Output

I generally don't recommend people use the XtremIO CLI for programmatic access - it's just so much easier and better to use the REST API. However there are occasions where using the CLI may make sense. Access to the CLI can be automated via SSH, and sending commands is relatively…

#Tags: xtremio, cli

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) default to…

#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' (or just…

#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

Hacking Package Pickup

Just over a week ago my apartment complex launched their new "Package Pickup Center" - an automated locker system much like those that Amazon and others are using to allow 24x7 collection of packages. Like all of these systems, it consists of a number of computer-controlled lockers, and a screen…

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The Latency/Threads Relationship and HA Testing

One of the most common mistakes people make when testing storage is that they think they are measuring IOPS or bandwidth, when all that they are actually measuring is latency. As a simple example, lets say that we have a storage device that takes 1ms to respond to an IO…

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