Author Archives: Cormac

Tweet sized vSphere Design Considerations – Call for Entries

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I’m delighted to be involved in an upcoming project on vSphere Design Considerations. This is the brain-child of my ex-colleague, Frank Denneman, who recently fu^H^H decided to broaden his horizons and join an interesting new start-up called PernixData. :-)

Also on the project are Duncan Epping (still a colleague), Jason Nash and the inimitable Vaughn Stewart of NetApp. To cut to the chase, the objective here is to create a pocket-sized book containing the best vSphere design considerations. However, the cool part of this book is that the community are the authors. And the book will be free, courtesy of PernixData. So if you have a best practice that you want to contribute, head on over to Frank’s web-site and read the instructions on how to submit.

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VAAI-NAS – Some snapshot chains are deeper than others

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This is something that was recently brought to my attention, and I wasn’t aware of this difference in behavior between the various storage vendors who implement VAAI-NAS. VAAI-NAS implements a number of different offload primitives, but the one we are interested in here is the Fast File Clone primitive which is the ability to offload the creation of snapshots/clones to the NAS storage array. This mechanism is also referred to as Native Snapshots. However, some arrays cannot support a full chain of snapshots.

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What happens when VMFS heap depletes completely?

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I’ve blogged about the VMFS heap situation numerous times now already. However, a question that I frequently get asked is what actual happens when heap runs out? I thought I’d put together a short article explaining the symptoms one would see when there is no VMFS heap left on an ESXi host. Thanks once again to my good friend and colleague, Paudie O’Riordan, for sharing his support experiences with me on this matter – “together we win”, right Paud?

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Heads Up! EMC VNX, Recoverpoint & VAAI

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I just got a notification about this myself today. Apparently there is some interop issues with VAAI (vSphere APIs for Array Integration) & EMC RecoverPoint on EMC VNX arrays. It looks like the VNX Storage Processor (SP) may reboot with Operating Environment Release 32 P204 in a RecoverPoint environment.

EMC have just released today a technical advisory – ETA emc327099 – which describes the issue in more detail but is basically advising customers to disable VAAI on all ESXi hosts in the RecoverPoint environment while they figure this out. Hopefully it won’t take too long to come up with a solution to allow VAAI run in these environments once again.

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Heads Up! UNMAP considerations when reclaiming more than 2TB

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Thanks to our friends over at EMC (shout out to Itzik), we’ve recently been made aware of a limitation on our UNMAP mechanism in ESXi 5.0 & 5.1. It would appear that if you attempt to reclaim more than 2TB of dead space in a single operation, the UNMAP primitive is not handling this very well. The current thought is that this is because we have a 2TB (- 512 byte) file size limit on VMFS-5. When the space to reclaim is above this size, we cannot create the very large temporary balloon file (part of the UNMAP process), and it spews the following errors:

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