FAST VP and FAST cache my experience so far....

Hi Guys

After many questions and reading some documnets this is what i have gathered so far about FAST VP, i thought it might be handy to have what i learned in 1 post to help some others out so here goes.

FAST VP

FAST VP works by gathering and monitoring statistics on data and determining which is HOT or COLD and this data is promoted or relocated in 1gb slices depening on its current assigned state (or weight) eg hot or cold (kind of shortened explaination i hope its ok)

3 RAID types which are RAID 5, 6 and1/0

recommended disk numbers for

RAID 5 multiple's of 5 (minimum of 3)

RAID 6 multiples of 8 (miminum of 4)

RAID 1/0 multiples of 8 (mimimum of 2) 

When you use the recommended disk numbers as above in your storage pools, the disks are configured as follows

RAID 5 every 5 disks are configured as 4+1 so if you have 20 disks in a pool that would be 4 x 4+1 RAID 5 groups

RAID 6 every 8 disks are configured as 6+2 so if you have 16 disks in a pool that would be 2 x 6+2 RAID 6 groups

RAID 1/0 every 8 disks are configured as 4 + 4 so if you had 16 disks in a pool they would be confiigured as 2 x 4+4 Raid 1/0 groups

When you create a pool you get three options Auto-tier, Highest Available and Lowest Available and auto-tier is the default. You get these options when you create a Pool LUN and not when you are creating a pool. FAST VP options are application at the LUN level

When you create a pool and add additional disks after,  the data will NOT be rebalanced across all the disks but EMC are looking at this to be added in a future release , link below has a very good storage pool overview

When adding drives to an already configured pool try add as many disks as possible eg if you originally had 10 disks add another 10 disks this helps prevent any performance degradation due to the pool not rebalancing as mentioned above and discussed in the link below.

http://virtualeverything.wordpress.com/2011/03/05/emc-storage-pool-deep-dive-design-considerations-caveats/

The rough ratio for a 3 tier pool is 5/25/75 so 5% EFD, 25% SAS and 75% NLSAS (VNX, i assume clariion is the same only FC and SATA)

you can also have 1 and 2 tier pools SAS or NL SAS or EFD which can be increased to 3 tier with EFD'S/SAS/NLSAS etc at a later stage

When using many NLSAS drives the recommended RAID type is RAID 6, this is due to the extended rebuild times of NLSAS and the chance of a double disk failure during a rebuild when using say RAID 5. But all depends on your performance and cost requirements RAID 5 or RAID 1/0 maybe required

RAW disk IOPS numbers

EFD = 2500 IOPS

SAS = 180 IOPS

NLSAS = 90 - 120 IOPS - i have seen varying numbers on this so i would go 100 to be conservative but i'm open to confirmation from you EMC guru's :-)

Raid Write Penalty

RAID 5 = 4

RAID 6 = 6

RAID 1/0 = 2

After some discussions on IOPS and storage pools the information i've received  is that you work out your IOPS as normal and factor in the relevant write penalty and when you have that number take away another 10% of that number to account for the storage pool overhead BUT i don't have confirmation from EMC on this maybe they will comment/confirm ?

As always the above are only guidlines if you do a full performance review of your customers storage environment you will have exact IOPS and capacity requirments which will determine your 3 tier configuration.

All correction's, suggestions and additions are welcome :-)

Right on to FAST CACHE

Ok FAST cache is where i hit some major issues on how to configure and best practice. I know there is a detailed document explaining the max sizes and how to turn on FAST cache and configure for POOLs and Traditional LUNs etc but there is very little on how much you should configure for a specific system with a certain amount of storage in it.

Basically after much discussion the answer is usually "how long is a piece of string" the baisc rule of thumb i came across was very roughly 5% of the total amount of storage in that system. The main explaination is you have to know your customer environment and basically do a performance analysis of the current environment which you can submit to your local EMC contact and they will work with you and the analysis to determine the best FAST cache configuration for your system.

Which i guess is good advice as you dont want to buy too many EFD's they're not cheap and you want to give your customer the best deal and performance.

If anyone has some real life VMWARE Vsphere FAST VP and/or FAST CACHE case studies, i would be forever greatful to have a look or even anyones experience with both FAST technologies

I hope someone will find the above useful and a big thanks to all the guys who answered all my FAST questions :-)