topic Re: EVA5000 - disk levelling - controller use in Disk Enclosures

EVA5000 - disk levelling - controller use

inex — Fri, 28 Jan 2011 22:44:58 GMT

We have an EVA5000. When adding more disk to a diskgroup and the system is doing levelling, will the EVA controllers be evenly used during this process?

-inex

Re: EVA5000 - disk levelling - controller use

Rick vonR — Sat, 29 Jan 2011 00:46:49 GMT

As far as leveling goes, the controllers will balance the load but at a low priority with respect to I/O requests. If you have a large number of disks in the group, leveling could take quite some time.
If you are referring to incoming requests and controller load balancing, I/O requests coming into ports on the array is dictated by the hosts attached to the array. If you have multiple EVA ports assigned to a host, that host determines on which path to send the I/O either by which port got assigned first or by the MPIO driver if one is being used.

Re: EVA5000 - disk levelling - controller use

inex — Sat, 29 Jan 2011 00:57:35 GMT

So lets say with no leveling, controller A has more i/o load than controller B. Then leveling starts, will this extra workload be split equally between controller A and B, or will controller B take more of this extra load, because it was less busy than controller A.

-inex

Re: EVA5000 - disk levelling - controller use

Rick vonR — Sat, 29 Jan 2011 01:08:28 GMT

It is based on priorities. If controller B has less incoming requests it will handle more of the leveling. But again, leveling will take a back seat to I/O requests.

Re: EVA5000 - disk levelling - controller use

Johan Guldmyr — Sat, 29 Jan 2011 07:16:03 GMT

I thought the leveling was handled only be the owning controller of the vdisk that's being levelled?