HP EVA6400 performance issues and FATA disks

[zeno75]

Hi there,

I'd like some advice on some issues were experiencing with our EVA6400. Currently were running the EVA6400 with VMware and some DB applications, the EVA is configured with 2 disk groups 190 FC and 14 FATA and we use the FATA for DB dump and then backup to tape.

We know that our FC disk group at times is quite busy and what we've found recently since we started using the FATA DG's is that  whenever writing to vDisks in this DG it significantly degrades the performance of all apps hosted on the FC DG to a point that our applications on the FC DG are starting to timeout and loose response.

Our original intention was to save cost and use the cheap FATA for DB dumps (usually 1 TB in size)and then backup to save cost but it seems we didn't forsee it would have such impact on the overall SAN performance that we may need to go back to using FC. Has anyone experience in using FATA for such use and some of the "caveats".

What were suspecting is our FC vdisks are dumping the DB's to the FATA vdisks and because the response IO's from the FATA DG is inadequate its creating some hot spots on the SAN and we get issues with cache usage causing all other applications on the FC DG to degrade significantly.

Anyone have some insight, many thanks.

[giladzzz]

Hi

FATA drives can effect your EVA performance by loading your controllers or your cache first of all check all your MPIO are defined with ALB enabled also you could put the vdisks on your FATA drives into write through mode to

prevent loading the cache of your EVA.

Regards

Press the kudo star if you liked

[Steven Clementi]

What raid level are the vDisks in the FATA DG?

Keep in mind that vRaid5 disks incur double the i/o penalty vs. vRaid1 vDisks.  In this instance, you are reading FROM FC disks TO FATA disks.  The read/write process might be causing issues in your virtual world... especially if you have ESX 4.0 or previous.

What version of ESX are you ruinning?

How many hosts are accessing the same vDisk?

How many VM's are on the same vDisks?

Is your multipath poilcy set to Round Robin? or the default?

[Prakash Singh_1]

Check the below settings:

1. MPIO is defined with ALB enabled 
2. Set your FATA vdisks into write through mode to Prevent loading the EVA cache.
3. Check the ESX version should be 4.0 or latest.
4. No. of Hosts accessing Vdisks.
5. Should Vraid 5 as it takes double IO for parity.