auto-path vs secure path and EVA vs XP arrays

[nucleon]

Hello,
We need to recommend a customer of our company a hp disk array hw & sw solution on enterprise linux systems. The solution should have multi-path and dynamic load balancing support.

We came across two software solutions on hp website:

1) HP secure path software
2) HP auto path software

We are a little confused. Could someone help us understand why HP has two solutions?

We need to understand the components of autopath software as well as secure path software.

We would like to get information on how much software is in kernel space and how much in user space for both the soltuions.

The customer would like to have an active/active configuration. We understand
XP arrays are active/active, but EVAs are not
at this moment.

Do we have performance figure for EVA and XP arrays?

Are XP arrays more performant than EVA arrays?

NucleoDyne Systems.

[Uwe Zessin]

AutoPath vs. Securepath:

AP is an original HP product. SP comes from the Digital/Compaq world. AP and SP provide multipath functionality for different storage arrays: AP = VA + XP, SP = RA/ESA/MA/EMA/MSA/EVA. If you carefully look, you will see that the 'autopath driver' is now sold under the Secure Path label, too.

Both, AP + SP have the same structure. They use a set of device drivers that understand how to work with a particular storage array and a 'filter driver' that makes sure that the upper layers only see a single device.

It is not important for the end-user to understand how much software lives in user or kernel space - it's a black box - you either take it or you don't.

Active/active...
There a different opinions on what defines an active/active configuration.

The EVA has two controllers and one controller 'owns' a virtual disk at a time. A host can do I/Os to both ports of this controller to talk to all virtual disks that are owned by him. An I/O to the other controller for an unowned virtual disk results in a 'not ready' response, because this controller does not re-route the I/O request to the owning controller like the VA storage array.

These virtual disks must still be presented through the non-owning controller so that the multipath software knows that there are standby paths it can fail over in case of an error. However, it does not really make sense to internally re-route the I/O request - see some documentation about the 'performance path' on a VA-series storage array.

An EVA usually has multiple virtual disks created and these can be more or less equally distributed over both controllers.

So, controllers are active/active. Virtual disks are not.

Performance...
ask two people and get 3 different opinions ;-)

The EVA is meant for easy setup and some self-tuning. I am not very familiar with the XP arrays, but no doubt, there are a lot more knobs to fine-tune the system.

> Are XP arrays more performant than EVA arrays?
Of course, that depends on the benchmark you ran. What result do you want? ;-)

It should be no problem for experts to find configurations where the EVA displaces the XP and vice versa. Still, when money is no deal, the XP is more high-end than the EVA.

[James Odak]

As we found out the very painful way

EVA3000 and EVA5000 with multi-pathing are not supported by HP wihtout secure path

EVA's 4000 6000 and 8000 are active/active however and can use PVLinks