Tag Archives: WRITE SAME

What’s New in Purity 5.1: WRITE SAME Handling Improvement

In Purity 5.1 there were a variety of new features introduced on the FlashArray like CloudSnap to NFS or volume throughput limits, but there were also a variety of internal enhancements. I’d like to start this series with one of them.

VAAI (VMware API for Array Integration) includes a variety of offloads that allow the underlying array to do certain storage-related tasks better (either faster, more efficiently, etc.) than ESXi can do them. One of these offloads is called Block Zero, which leverages the SCSI command called WRITE SAME. WRITE SAME is basically a SCSI operation that tells the storage to write a certain pattern, in this case zeros. So instead of ESXi issuing possibly terabytes of zeros, ESXi just issues a few hundred or thousand small WRITE SAME I/Os and the array takes care of the zeroing. This greatly speeds up the process and also significantly reduces the impact on the SAN.

WRITE SAME is used in quite a few places, but the most commonly encountered scenarios are:

Pure Storage and VMware VAAI

Today I posted a new document to our repository on purestorage.com: Pure Storage and VMware Storage APIs for Array Integration—VAAI. This is a new white paper that describes in detail the VAAI block primitives that VMware offers and that we support. Furthermore, performance expectations are described, comparing before/after and how the operations do at scale. There are some best practices listed as well, the why and how of those recommendations are also described within.

I have to say, especially when it comes to XCOPY, I have never seen a storage array do so well with it. It is really quite impressive how fast XCOPY sessions complete and how scaling it up (in terms of numbers of VMs or size of the VMDKs) doesn’t weaken the process at all. The main purpose of this post is to alert you to the new document but I will go over some high level performance pieces of information as well. Read the document for the details and more.


vaai_pdf_cover

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VMware VAAI with EMC ScaleIO

I’ve started recently playing a lot with EMC ScaleIO (version 1.2 just came out) and deployed it in my VMware environment. VERY easy to deploy and use.

During my investigation of the product I noticed in the vSphere Client that my ScaleIO datastore was marked as supported for VAAI. I looked around for some documentation saying so and I haven’t been able to find any off the bat (if anyone does let me know).

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VMAX and VMware VAAI White Paper Update

One of the documents that my colleague Drew Tonnesen (@drewtonnesen) and I maintain is a white paper that explains the how, what, why, when, etc. of  using VMware’s VAAI block primitives (WRITE SAME, XCOPY, ATS and UNMAP) with Symmetrix VMAX storage systems. We update this document around twice a year or as needed to take into account new Enginuity releases or VMware releases. We just posted the latest update this weekend on EMC’s website:

http://www.emc.com/collateral/hardware/white-papers/h8115-vmware-vstorage-vmax-wp.pdf

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