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* Posts by jspiers

3 publicly visible posts • joined 14 Feb 2012

Networked mutant flash-disk beast Nimble to smack flashy rivals with 'high-end' boxen

jspiers
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Re: FUD Alert

Yes, FUD alert, good job, and I'm not trying to hide who I am. An SVP in title, but an engineer at heart. Do the math - a shelf of SSDs behind a 6Gbps SAS drive cable and disk controller, the same controller that's feeding all the disks in the head unit as well. These legacy SSD bolt-ons to disk architectures will go away, it's just a matter of time, and who knows, Nimble may move away from it as well some day.

With regards to the question on why active-active matters, why don't you ask Dell HP, EMC, NetApp and just about everyone else that makes an enterprise class storage solution why it matters, because they are all active-active. Why have half of your resources sitting idle?

John

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jspiers

The dirty little secret is that all this flash is still connected to a single, legacy disk drive controller. Remember, Nimble is active-passive, so there is only one LSI disk controller feeding all this flash. My guess is that the IOPS specs are generated out of NVRAM. Ask them for large sequential IO data for different sizes of flash and you will see it doesn't scale performance as you add flash. It can't go any faster than the one PCIe slot the controller is plugged into, and IO contention through a single, shared disk controller must be horrible. Bottom line: if flash devices are not on their own PCIe bus then the architecture is bottlenecked and will become obsolete very soon. If you don't believe me stay tuned.

John

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NexGen boss: If solid hardness isn't stuck into PCIe - forget it

jspiers
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Re: Umesh

The facts speak for themselves. The maximum throughput to the backend disk subsystem through a RAID storage controller (storage HBA) is the bandwidth of the PCIe slot that the HBA is plugged into. Now if one solid state device can saturate an x8 PCIe slot, then the storage HBA is bottlenecked with one drive, let alone many SSD drives combined with many rotating drives. It's like placing RAM behind a drive HBA. Realistically, most of the storage HBAs on the market can’t even come close to x8 throughput because of other bottlenecks and overheads. One NexGen SSD device runs at x8 line rate, it can be shared across storage processor domains, and can be serviced non-disruptively. For more details see NexGen's blog on this subject:

http://nexgenstorage.com/ssd-big-technical-illusion

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