I’ve been hit up this week by a number of folks asking about “ATS Miscompare detected between test and set HB images” messages after upgrading to vSphere 5.5U2 and 6.0. The purpose of this post is to give you some background on why this might have started to happen.
In vSphere 5.5U2, we started using ATS for maintaining the heartbeat. Prior to this release, we only used ATS when the heartbeat state changed. For example, referring to the older blog, we would use ATS in the following cases:
Acquire a heartbeat
Clear a heartbeat
Replay a heartbeat
Reclaim a heartbeat
We did not use ATS for maintaining the ‘liveness’ of a heartbeat. This is the change that was introduced in 5.5U2 and which appears to have led to issues for certain storage arrays.
There was a time when VMFS was the only datastore that could be used with ESXi. That has changed considerably, with the introduction of NFS (v3 and v4.1), Virtual Volumes and of course Virtual SAN. However VMFS continues to be used by a great many VMware customers and of course we look to enhance it with each release of vSphere. This post will cover changes and enhancements to VMFS in vSphere 6.0.
Regular readers of my VMware Storage Blog will be no stranger to Nimble Storage. I’ve blogged about them on a number of occasions. I first came across them at a user group meeting in the UK & I also wrote an article about them when they certified on VMware’s Rapid Desktop Program for VDI.
Nimble Storage have been in touch with me again to share details about their new 2.0 storage architecture. After a very interesting and informative chat with Wen Yu of Nimble, I’m delighted to be able to share these new enhancements with you, in this first post on my new blog site.
Nimble Storage’s new enhancements can be categorized into two areas. The first of these is a new scale out architecture and the second is further integration with vSphere.
Scale to Fit
Scale to Fit architecture is how Nimble Storage describe their new elastic scaling feature. It basically allows customers to scale out their storage on a particular dimension, be it capacity or performance. This new architecture allows customers to start with a small footprint, and then to scale performance and capacity. This can be done without having to migrate any data and without any Virtual Machine/application downtime. The great advantage of this of course is that it avoids over-provisioning of storage up front, keeping initial costs down. When additional performance or capacity is needed, customers only need to grow on that dimension. This means that customers don’t pay for additional performance if they only need capacity, and vice-versa.
vSphere Integration Features
There are 3 new vSphere integration features to call out in this new release.
Nimble Storage have a new Storage Replication Adapter (SRA) for integrating with VMware Site Recovery Manager (SRM). Business Continuance and Disaster Recovery are essential features for any enterprise class storage array, and it is great to see that Nimble now offer full integration with VMware’s BC/DR flagship product.
There are a number of additional VAAI offload primitives supported. The first of these is Hardware Assisted Locking (ATS) which enables ESXi hosts to offload VMFS volume locks to the Nimble storage array. The second is the UNMAP primitive, which enables VMFS volumes built on thin provisioned disks to do space reclamation after storage vMotion or VM deletion. If I remember correctly from previous conversations with Nimble, they already support the WRITE_SAME primitive.
This last feature is the one I am most excited about. Nimble Storage now offer their own Path Selection Plugin (PSP) into the Pluggable Storage Architecture of the VMkernel. This optimized multipathing plugin will load balance I/O, and provide linear performance scalability with a single Nimble storage array or multiple storage arrays in a scale-out cluster. The PSP is called Nimble_PSP_Directed.
Nimble Storage are a sponsor at the VMworld 2012. You’ll find them at booth 306 at the US conference this year.
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