What are your plans for deploying Flash/SSD storage?

Hello,

We have implemented flash as FAST Cache in one of our CX4-240 arrays few weeks back and are implementing it on our second CX4-240 as I write this (flare 30 upgrade ongoing). First I was a little disappointed on FAST Cache as it didn't speed up writing to SATA drives as I thought, I was doing a lot of LUN migrations from old RAID Groups to new Storage Pools and FAST Cache wasn't helping on throughput at all. After closer investigation to documentation and getting confirmation from ENC forums I understood that blocks have to be promoted to FAST Cache before it actually starts buffering writes.

Now that new Storage Pools have been in place for some time we are seeing very high hit rate on FAST Cache, both for writes and reads. During normal business hours FAST Cache write hit ratio is 80-90% and read hit ratio is over 50% most of the time. Workload is very random, we are a hosting provider so these arrays are in multi-tenant use. There is Exchange, MS SQL, Oracle databases, MySQL, web servers, vSphere virtual machines, file servers, SAP, you name it. Array response times are very good because of FAST Cache, even though that storage processors CPU utilization gets very high during busiest hours.

I think FAST Cache is great feature, but it sure takes lot of storage processor resources to handle the amount of IOPS you are getting from you array with flash storage.

Greetings!!

Thanks for sharing your experience with FAST Cache.

It is true that FAST Cache goes through a 'warm-up' phase while frequently accessed data is promoted from backend to the FAST Cache. I think that is what you experienced as well.

It is good to hear that you are seeing good performance with FAST Cache after the initial warm-up phase.

I presume your workload is often heavy and that may result in frequent promotion and eviction of chunks to and from FAST Cache. This would result in system resource utilization including CPU cycles. As long as you are seeing good response time, it would indicate you are within system's limits and hitting higher CPU utilization is not necessarily a bad thing.

What is the configuration of the backend storage for the LUNs that have FAST Cache configured? Is it FC drives or SATA drives?

Allen - It is great to hear that you are looking at deploying FAST with multiple tiers, Flash being one of them.

Flash in the tier is certainly the way to get your most active data the best response time from Flash tier in the pool and as your data will age (expected for almost all data types), depending upon the policy, but if the policy is set to Auto-Tier the data when is less frequently access will be moved to lower tier - FC/SAS or SATA/NL-SAS.

Please share your experience with us as you go through this implementation and if you like to discuss anything here at the forum.

I should have mentioned as well that we will definitely be deploying  SSD for FAST Cache. As far as I'm concerned that is kind of a "no brainer" if you are already paying the licensing. Not enabling FAST Cache would just be a waste of money (except in some VERY specific situations that most people won't ever experience)