Clariion CX480 Fast Cache vs SP Cache

Question

Hi all

i have an CX480 with FC 15K disk for database lun and 2 raid group with SATA2 disk for other data.

The two SP are often between 70 to 80 % use and some times the Cache Ps are full to 100 % and some database become so slow that we have an

production disaster ..

For avoid this we buiy SSD disk and build a Fast Cache , 92 GO..

ichange the metalun properties for database for use the fast cache..

But for SATA Lun , i have to choice..

-> remove all cache acces for preserve SP Cache but the flow become really slow

-> use only Fast Cache for SATA Lun, without SP Cache ! it is possible with unisphere but, i don't know if it is a good idea

does anyone have an idea or an expérience return about enable FastCache for a Lun witout SP cache ? ?

thanks to all and good week-end

Pascal

Anonymous User · Answer

Hi Pascal, How are you doing today…? Please refer Primus 'emc251589  and emc260951 '… Regards, Suman Pinnamaneni

isildur2 · Answer

Hi Suman

fine , and you ? the summer begin in my country ..

thanks , i know this primus..

but they don"t say if i can use fastCache for lun, without SP cache first..

that seems strange but it is a way for preserve the SPcache for FC lun and fastcache for SATA LUN...

good evening

AnkitMehta · Answer

If I understood your issue correctly,

You have a CX4-480 with 15k/rpm FC disk for Database LUNs and 2 RAID Group with SATA2 Disks for other data.

The SP Utilization is almost 70-80% and at times SP Cache is 100%, because of which you are facing database performance issue which leads to production disaster.

To avoid the production disaster further, you have purchased SSD Disks and FAST Cache enabler.

You are using FAST Cache now for Database LUNs and which is working fine.

However, for SATA disk based LUN, you are not sure whether to,

- Make LUNs skip SP Cache and avoid forced flushing.

- Use only FAST Cache for SATA Disk based LUNs with out SP Cache.

It would be difficult to say with out checking the NAR files when it comes to Array/LUN Performance.

Assuming just leads to chaos. It would be best if we do not assume here which one would work out better for you and choose one answer which might lead to chaos.Moreover, it also depends on What type of data you have on SATA2 based RAID Group? What type of Application you are using on those LUNs?

IOPs are sequential, random, big chunks etc..

I would suggest you to open a Service Request with EMC Technical Support with fresh Set of SP Collects (from both SP's) as well as NAR files attached.

Thorough analysis would determine what is causing high utilization and followed by a recommendation to reduce it, if possible.

zhouzengchao · Answer

Ok, there are two problems:

(1) both SP CPU reached 70-80% UT often.

(2) SP Cache reached 100% Full often.

My question is, does the addition of FAST Cache reduced your SP UT? If not, I think FAST Cache won't help much.

As AnkitM said, if your SATA LUN would benifit from FAST Cache is much more depends on the workload.

RRR · Answer

I suspect adding FAST Cache will cause your cache not filling up so fast anymore, but the cpu utilization won't probably go down (much).

CLARiiON

Clariion CX480 Fast Cache vs SP Cache

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