VAAI UNMAP Performance Considerations

I was involved in some conversations recently on how the VAAI UNMAP command behaved, and what were the characteristics which affected its performance. For those of you who do not know, UNMAP is our mechanism for reclaiming dead or stranded space from thinly provisioned VMFS volumes. Prior to this capability, the ESXi host had no way of informing the storage array that the space that was being previously consumed by a particular VM or file is no longer in use. This meant that the array thought that more space was being consumed than was actually the case. UNMAP, part of…

Heads Up! VAAI UNMAP issues on EMC VMAX

We just got notification about a potential issue with the VAAI UNMAP primitive when used on EMC VMAX storage systems with Enginuity version 5876.159.102 or later. It seems that during an ESXi reboot, or during a device ATTACH operation, the ESXi may report corruption. The following is an overview of the details found in EMC KB 184320. Other symptoms include vCenter operations on virtual machines fail to complete and the following errors might be found in the VMkernel logs: WARNING: Res3: 6131: Invalid clusterNum: expected 2624, read 0 [type 1] Invalid totalResources 0 (cluster 0).[type 1] Invalid   nextFreeIdx 0…

vSphere 5.5 Storage Enhancements Part 4: UNMAP

Continuing on the series of vSphere 5.5 Storage Enhancements, we now come to a feature that is close to many people’s hearts. The vSphere Storage API for Array Integration (VAAI) UNMAP primitive reclaims dead or stranded space on a thinly provisioned VMFS volume, something that we could not do before this primitive came into existence. However, it has a long and somewhat checkered history. Let me share the timeline with you before I get into what improvements we made in vSphere 5.5.

vSphere 5.1 Storage Enhancements – Part 2: SE Sparse Disks

This is possibly the most exciting new storage feature in the vSphere 5.1 release. Space Efficient Sparse Virtual Disks (or SE Sparse Disks for short) were designed to alleviate two issues. Let’s describe these issues first of all. Problem Statement #1 – Let’s take a Guest OS running on a linked clone (View desktop if you will), and this Guest OS issues a 4KB write. vmfsSparse disk (which is the format used by traditional linked clones) has a block allocation unit size of 512 bytes. In other words, this Guest OS is backed by 512 byte blocks. Depending on the…

Nimble Storage 2.0 Architecture Updates

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…