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July 10, 2012

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Dmitri Kalintsev

Hi Chuck,

As VPLEX is sitting in the data path, it surely has an opportunity to become a bottleneck for storage performance - both throughput and latency wise. How is this potential problem addressed by VPLEX's architecture?

Cheers,

-- Dmitri

Chuck Hollis

Hi Dmitri

It's not the problem you might think in the majority of situations, just as it's not usually a problem for NAS heads, replication engines, and other black boxes you'll routinely see in the data path.

First, the tech (CPU, memory, bus, I/O chips, etc.) is wicked fast these days -- these are the same components and designs we use to build storage array controllers. The VPLEX design is derived from the VMAX storage director, if that's any consolation.

The other significant factor is that there's almost always some sort of caching or SSD use going on in these environments. The VPLEX itself does selective caching, but it also can happen in many other places in the I/O stack. If there's concern about response time, a bit more flash in the shared I/O pool is a great compensator.

Is there some theoretically measurable latency when you introduce something (anything) into an I/O path? Yes, of course. Is it meaningful latency? Usually it's not an issue with the vast majority of situations.

-- Chuck

Dmitri Kalintsev

Hi Chuck,

Thank you for the further details; the VMAX pedigree does indeed make things interesting.

Reading http://www.emc.com/collateral/hardware/technical-documentation/h7113-vplex-architecture-deployment.pdf now; looks like I should be able to find answers to all further questions in there. :)

-- Dmitri

Chad Sakac

Further dimitri, chuck - it scales out locally - up to 8 engines (for now). A single VPLEX engine adds basically no latency (helps in some cases as it is a cache also), and can do about a million iops. Pretty wicked fast.

Disclosure - EMCer here!

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Chuck Hollis


  • Chuck Hollis
    Chief Strategist, VMware SAS BU
    @chuckhollis

    Chuck has recently joined VMware in a new role, and is quite enthused!

    Previously, he was with EMC for 18 years, most of them great.

    He enjoys speaking to customer and industry audiences about a variety of technology topics, and -- of course -- enjoys blogging.

    Chuck lives in Holliston, MA with his wife, three kids and four dogs when he's not travelling. In his spare time, Chuck is working on his second career as an aging rock musician.

    Warning: do not buy him a drink when there is a piano nearby.
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