Jacob Wilkins (5/24/2015)

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We have a bunch of Nimbles in our customers' environments, and depending on your performance requirements, they can be hard to beat for performance/price.

Having said that, there are not "tiers", per se, at least not in the sense of traditional tiered storage like EMC.

There are back-end SATA disks (12 unless you add a capacity shelf, I believe), and then an all-flash cache. The auto-tuning is just moving data in and out of the cache and directing sequential IO to the SATA.

As iannoble pointed out, write performance is generally very good, since it writes to NVRAM, and reads are also fantastic provided they come from cache.

That last point is the big caveat. If a significant bit of IO ends up coming from the back-end SATA disks, whether because you're churning through the cache or the IO is classed as sequential and goes straight there, performance can tank, since 12 SATA disks can only deliver so much performance.

We've run into the biggest problems with that when running CHECKDBs or when customers have very large active data sets that can overrun the cache.

The performance drop from going to those disks is enough that we've basically adopted a policy only to order them with the 4x cache upgrade, since most of the units we ordered with base cache turned out to have huge cache churn issues, and resulting IO issues with too much hitting the SATA disks.

So long as you make sure the cache is adequately sized for your active data set, you should get great performance from them, especially for the price.

Cheers!