topic Re: EVA 8100 Controller Usage in Disk Enclosures

EVA 8100 Controller Usage

Sajeev2007 — Thu, 06 Dec 2007 19:38:47 GMT

On the EVA 8000, you assign a LUN to a controller and that controller, controls the LUN and unless there is a failure in which case the control is passed on to the other controller.

For the 8100 i heard that it will load balance between controllers. is this possible ?

my concern was if i have to alllocate 4 TB to a server, as an example, i split it into 500GB each and specify the controller A or B for each LUN on 8000 for load balancing

But for 8100 i can just allocate a 2 TB Lun and then the controllers will load balance.

is this correct for the 8100

thanks

Re: EVA 8100 Controller Usage

Víctor Cespón — Thu, 06 Dec 2007 21:39:55 GMT

Actually, each vdisk is "owned" by a controller and that controller handles all the traffic to that vdisk. If a request comes from the other controller, it passes the request to the "owner" controller. If more than 60% of the requests come from the wrong controller, the vdisk switches ownership to that controller.

The EVA 8100 has a new (faster) PowerPC processor, and the enclosures (M5314C) that have switching I/O modules.

- New EVA's fully switched architecture and multiple redundant paths from the controllers to the disk drives provide better data availability compared to traditional arbitrated loop connectivity.

- New controllers with 50 to 70% improvement in cache throughput and up to 24% improved performance

The maximun size for a virtual disks is still 2047 GB.

Re: EVA 8100 Controller Usage

Ivan Ferreira — Thu, 06 Dec 2007 21:40:40 GMT

>>> my concern was if i have to alllocate 4 TB to a server, as an example, i split it into 500GB each and specify the controller A or B for each LUN on 8000 for load balancing

Yes, this can be done, but this is from the storage side point of view.

You should also think in the host access patters. If you have multipath software, you should check the load balancing algorithm used by it. Having proxy I/Os could reduce the performance.

This mean that, if you split 4 TB into 500 GB vdisks, distributing between the controllers and you present all to the same host, and the host has 2 HBA, and the access mode is round robin, half of your access will be done using Proxy I/O, that is, accessing the vdisk using the "not owner" controller.

Re: EVA 8100 Controller Usage

Sajeev2007 — Fri, 07 Dec 2007 02:42:22 GMT

ok then whats the best method to configure ? Large size LUNs or multiple Small LUNs ?
For Eg. in an exchange server should i create multiple VDISks for each storage and logs ? or one large vdisk and then partition it on the host ?

and why would you do it that way ?

Thanks

Re: EVA 8100 Controller Usage

Tony Valentim — Sun, 23 Dec 2007 19:28:15 GMT

I'm a fan of multiple luns. If oyu make 1 lun you guarantee all the load will be on 1 controller. If you make multiple luns you will use multiple controllers and have multiple IO queues from a OS perpective

Re: EVA 8100 Controller Usage

Oktovianus — Fri, 25 Jan 2008 09:57:12 GMT

Hi guys,
Is the LUN balancing only consider the quantity of the LUNs or the sizes also?
For example if I have to allocate 3TB to a server, then I separate it into 4 vdisks (1.5TB,1TB,500GB,500GB), is it OK if I put 1.5TB + 1TB to controller A and double 500GB to controller B? (2.5TB vs 1TB)
or should I consider about the LUN sizes also then I pick 500GB + 1.5TB in controller A and 1TB + 500GB in controller B?

Thnx..