Implementing FAST CACHE on CX4-480

Question

All,

I think we're about to bite the bullet on FAST2, and we would like to implement FAST cache. We currently have 5 x 200GB EFD's. What is everyone's recommendation on how much we should allocate for FAST Cache? I know..."it depends!"

Initially, we purchased the EFD's to be able to put our SQL data on them. I was going to configure it using 4+1. Since that SQL data is not 800GB, I was also thinking of housing the Index and tempDBs. Currently, we have a MS CRM server that has well over 45 fibre spindles on the backend. Because the application is heavily customized, the application doesn't perform well even with that many spindles. The SQL data is on a 15 spindle configuration with 90% read, 10% write ratio.

My thoughts on the FAST Cache was to implement 2 x 200GB as a RAID10, and then use the rest for some other data LUN. Do you think I'll get better performance just using all the EFD's for FAST Cache, and possibly my money's worth? Pros and cons to "all fast cache" or "some fast cache and some for data?"

I see us implementing this technology in less than a month so your responses would be appreciated. You can also provide me any best practices that's available.

thanks in advanced!

j

Kumar_A · Accepted Answer

On a CX4-480, you can create FAST Cache in only two configurations using 200GB flash drives:

1. Use eight 200GB flash drives to create 800GB of FAST Cache.

2. Use four 200GB flash drives to create 400GB of FAST Cache (this requires FLARE 04.30.000.5.507 or later).

Details about all the possible configurations on various CX4 models can be found in the FAST Cache whitepaper on Powerlink.

Kumar_A · Answer

The whitepaper is getting updated currently with the new configuration that you mentioned.

The internal RAID configuration is fixed at RAID 10 for data redundancy purposes and not configurable by the user.

odurasler · Answer

Thanks AVI for reply.

I'm assuming the White Paper, "EMC Clarrion and Celerra Unified FAST Cache" is outdated base on your info that I can use 4 x 200GB drives?

It looks like I'll have a very expensive hot spare. I wonder why the configs have to be R10? Is it because for the write penalty on R5?

odurasler · Answer

I'm assuming that if I were to do a 4x200GB Fast Cache that I can easily expand to it's maximum (8x200GB) in the future? Would that require a complete redo of FAST Cache at that point or a simple 'expand'?

jps00 · Answer

You cannot create a FAST Cache on a CX4-480 with fewer than eight 200GB flash drives.

The provisioning of FAST Cache with flash drives has limited configurations. Table 3 in Appendix A of EMC CLARiiON and Celerra Unified FAST Cache white paper shows the available configurations. In addition, Table 26 of EMC CLARiiON Best Practices for Performance and Availability FLARE Revision 30.0 contains the same information, although in a different format. Both of these papers are available on Powerlink.

Finally, I verified it myself on a CX4-480 with 200GB flash drives running FLARE 30.0; the wizard will not allow creating a FAST cache with four drives.

odurasler · Answer

Hmmm...even the primus, http://knowledgebase.emc.com/emcice/documentDisplay.do;jsessionid=E65E816747CAF5477A0333F634784876?docType=1006&clusterName=DefaultCluster&resultType=5002&groupId=1&page=&docProp=$solution_id&docPropValue=emc251589&passedTitle=null, states that 4x200 could be used.

* 400 GB Cache option for CX4-480 requires Release 30.5 or higher flare

jps00 · Answer

OK.  I stand corrected. With FLARE 4.30.000.5.50X (FLARE 30.5) a FAST Cache on a CX4-480 with four 200 GB flash drives can be created.

odurasler · Answer

thanks for verifying that for me. i would hate to bite the bullet and find that we couldn't implement FAST because we 'missed' a thing or two...OR we needed to purchase additional HW.

is emc offering training on FAST?

Kumar_A · Answer

As mentioned in the FAST Cache whitepaper on Powerlink, you cannot 'expand' a FAST Cache as you are suggesting. You would need to destroy the current FAST Cache and then create a new one.

Allen Ward · Answer

Good question on the training. I would hope that soon new training material would be available for the traditional courses that would include this information, but more importantly that there would be a significant update to the CLARiiON Performance Workshop. I've been planning on taking that for some time, but would hold off if I knew that update was coming.

CLARiiON

Implementing FAST CACHE on CX4-480

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