In vSphere 6.0, an improvement has been made to how we handle I/O issues, such as flaky drivers, misbehaving firmware, dropped frames, fabric disruption, dodgy array firmware, and so on which can cause I/O failures. The issue is that, previously, we continually retry these sorts of I/O errors, which can lead to all sorts of additional problems. In this release we are changing our behaviour for marking a path dead.
Nimble Storage are another company who have been making a lot of waves in the world of storage in recent years. Based in San Jose, CA, they IPO’ed earlier this year, and have something in the region of 600 employees worldwide at the present. I caught up with Wen Yu, who I have known from my early days at VMware where we worked together in the support organization. Wen moved over to Nimble a couple of years back and now is a technical evangelist at Nimble. Actually, Nimble were the subject of the very first post on this blog site when I launched it almost 2 years ago. At the time I wrote about some significant architectural updates in their 2.0 release. My understanding is that their next major release (2.1) is just around the corner. So this was a good time to chat with Wen about some new features and other things happening in the Nimble world.
I thought it was about time that I looked at some of the larger storage vendors closer to home. One of these is of course Bull. This company is probably more familiar to those of us based in Europe rather than those of you based in the Americas or Asia Pacific. However VMware customers in EMEA will have seen them in the Solutions Exchange at VMworld Europe, where they have a reasonably large presence. After some conversation with my good pal Didier Pironet, whom I’ve met at a couple of recent VMUGs, I was introduced to Philippe Reynier who is a manager in the Bull StorWay Competence Center and Solution Center. Philippe provided me with a lot of good detail on Bull’s storage solutions which I will share with you here.
There are many occasions where the information displayed in the vSphere client is not sufficient to display all relevant information about a particular storage device, or indeed to troubleshoot problems related to a storage device. The purpose of this post is to explain some of the most often used ESXCLI commands that I use when trying to determine storage device information, and to troubleshoot a particular device.
This is a topic which has been discussed time and time again. It relates to an advanced storage parameter called Disk.SchedNumReqOutstanding, or DSNRO for short. There are a number of postings out there on the topic, without me getting into the details once again. If you wish to learn more about what this parameter does for you, I recommend reading this post on DSNRO from my good pal Duncan Epping. Suffice to say that this parameter is related to virtual machine I/O fairness. In this post, I’ll talk about changes to DSNRO in vSphere 5.5.
A number of you have reached out about how to change some of the settings around path policies, in particular how to set the default number of iops in the Round Robin path selection policy (PSP) to 1. While many of you have written scripts to do this, when you reboot the ESXi host, the defaults of the PSP are re-applied and then you have to run the scipts again to reapply the changes. Here I will show you how to modify the defaults so that when you unclaim/reclaim the devices, or indeed reboot the host, the desired settings come into effect immediately.
In this post, I want to look at some fail-over and load balancing specific to ALUA (Asymmetric Logical Unit Access) arrays. In PSA part 3, we took a look at the different Path Selection Plugins (PSP), but for the most part these were discussed in the context of Active/Active arrays (where the LUN is available on all paths to the array) and Active/Passive arrays (where the LUN is owned by one controller on the array, and is only visible on the paths to that controller). ALUA provides a standard way for discovering and managing multiple paths to LUNs. Prior to ALUA, hosts need to use array vendor-specific ways to inquiry target port state. ALUA Provides a standard way to allow devices to report the states of its ports to hosts. The state of ports can be used by hosts to prioritize paths and make fail-over/load balancing decisions.