This doesn’t come up very often these days, but every once and awhile it does and every time it does, I look to see if we have documentation on it and there never seems to be. After writing this post I did find a forum post where my friend Drew answers it there too. Well anyways let’s quickly explain the situation.
Most block vendors these days tell customers to change their path switching policy for their storage in ESXi from the default of Round Robin (1,000) to 1. This makes ESXi switches logical paths for a given device after every I/O instead of every 1,000. The reason I say this doesn’t come up much anymore is that in modern version of ESXi (6.0 express patch+, 6.5 U1+ and 6.7+) we (Pure) have rules in ESXi that makes sure this is set by default without any user configuration. Many other vendors do as well.
Anyways, when using VMware tools to see if a device is configured properly, depending on how it is set, it can readout differently.
Continue reading Demystifying IO Operation Readouts in ESXi
This is my first (but certainly not last post) on the new path selection policy option in vSphere 6.7 Update 1. In reality, this option was introduced in the initial release of 6.7, but it was not officially supported until update 1.
So what is it? Well first off, see the official words from my colleague Jason Massae at VMware here:
Why was this PSP option introduced? Well the most common path selection policy is the NMP Round Robin. This is VMware’s built-in path selection policy for arrays that offer multiple paths. Round Robin was a great way to leverage the full performance of your array by actively using all of the paths simultaneously. Well…almost simultaneously.
Continue reading Latency Round Robin PSP in ESXi 6.7 Update 1
As you might have noticed vSphere 6.5 Update 1 just came out (7/27/2017) and there are quite a few enhancements and fixes. I will be blogging about these in subsequent posts, but there is one that I wanted to specifically and immediately call out now.
Round Robin and IO Operations Limit of 1 is now default in ESXi for the Pure Storage FlashArray! This means that you no longer need to create a custom SATP rule when provisioning a new host or adding your first FlashArray into an existing environment. Continue reading NMP Multipathing rules for the FlashArray are now default
This was a fun one. I’ve posted in the past about changing and removing a SATP rule. That post, however, only works if the SATP rule is valid and you want to change or remove it for whatever reason. I am going to re-use the same image I made for that previous post, because it still holds true:
Anyway. The issue: Continue reading Removing an incorrect SATP Rule
This is a topic I have posted about in the past but this time I am going to speak about it with the Pure Storage FlashArray. Anyone familiar with the VMware Native Multipathing Plugin probably knows about the Round Robin “IOPS” value which I will interchangeably also refer to as the IO Operation Limit. This value dictates how often NMP switches paths to the device–after a configured number of I/Os NMP will move to a different path. The default value of this is 1,000 but can be changed to as low as 1. For the highest performance Pure recommends changing this setting to 1 for all devices. The tricky thing is that it has to be done for every device on every host and doing this in a simple way isn’t immediately obvious. But here is the procedure.
Continue reading Changing the default VMware Round Robin IO Operation Limit value for Pure Storage FlashArray devices