One of the most common issues I got questions about in VSAN 5.5 was “why is VSAN deploying thick disks, when all of the documentation stated that VSAN deploys thin disks”? The answer was quite straight forward, and was due to the fact that the VMs were being deployed without a VM Storage Policy. This meant that it went through the standard VM deployment wizard which offered administrators the option of thin, lazy-zeroed thick (LZT) and eager-zeroed thick (EZT). The default option is LZT, which if you just do click-click-click (just like I do) when deploying a VM, then you…
I learnt something interesting about Virtual Volumes (VVols) last week. It relates to the way in which snapshots have been implemented in VVols. Historically, VM snapshots have left a lot to be desired. So much so, that GSS best practices for VM snapshots as per KB article 1025279 recommends having on 2-3 snapshots in a chain (even though the maximum is 32) and to use no single snapshot for more than 24-72 hours. VVol mitigates these restrictions significantly, not just because snapshots can be offloaded to the array, but also in the way consolidate and revert operations are implemented.
There are a couple of key concepts to understanding Virtual Volumes (or VVols for short). VVols is one of the key new storage features in vSphere 6.0. You can get an overview of VVols from this post. The first key concept is VASA – vSphere APIs for Storage Awareness. I wrote about the initial release of VASA way back in the vSphere 5.0 launch. VASA has changed significantly to support VVols, with the introduction of version 2.0 in vSphere 6.0, but that is a topic for another day. Another key feature is the concept of a Protocol Endpoint, a logical I/O…
In a previous post, I discussed the difference between a component that is marked as ABSENT, and a component that is marked as DEGRADED. In this post, I’m going to take this up a level and talk about objects, and how failures in the cluster can change the status of objects. In VSAN, and object is made up of one or more components, so for instance if you have a VM that you wish to have tolerate a number of failures, or indeed you wish to stripe a VMDK across multiple disks, then you will certainly have multiple components making…
In this post, we talk about a particular behaviour with using the default (or None) policy with VSAN. I have stated many times in the past that when a VM is deployed on the VSAN datastore, it behaves like it is thinly provisioned unless the capability ‘Object Space Reservation’ (OSR) is specified in the VM Storage Policy. The OSR will pre-allocate space on the VSAN datastore for the virtual machine’s storage objects, and is specified as a percentage of the actual VMDK size. However, there is a slightly different behaviour when the default policy is used. Once again, I was…
Last week I had the opportunity to catch up with Mike Koponen and Dean Steadman of Fusion-io. I had met with Mike and Dean at VMworld 2013, and spoke to them about the Fusion-io acquisition of NexGen storage earlier last year, and what plans Fusion-io had for this acquisition. Well, the result is ioControl Hybrid Storage, and we discussed some of the architecture of ioControl as well as a number of vSphere integration points.
Another session that I attended during the UK National VMUG earlier this month was an overview of Coraid Technology from Max Brown, one of Coraid’s System Engineers based in the UK. My first introduction to Coraid was at VMworld 2011 & I did a short overview of their AoE (ATA over Ethernet) solution here. I wanted to get along to this session to see what had changed since then. In a nutshell, Coraid present SAN storage as local storage via AoE. How do they do that? Well, Coraid provide the HBA, the AoE initiator software (which must be installed on…