High stripe crossing with diskpart

Which Flare code are you running ?

Have a read through " EMC Clariion Best Practices for performance and Availability: Release 28.5 Firmware Update".  There a similar document for Flare 29 as well.

Look at the alignment section, around page 20, it's a good explanation, and discusses where you will see benefits, not all environments, and it all depends on the operating system, the  application, the IO size wriiten, the Raid group and the spindle count, and how much you've aligned by.

Did you also run your tests on the same type of LUN and Raid Group with no alignment set? what were the results ?

You will get crossings, but they should be reduced, by what percentage depends on the I/O size been written.,

There is an easy formula in the FLARE 26 paper which you can use to calculate the approx percentage decrease in crossings, by aligning.

Percentage of data crossings = (I/O size) /(stripe element size) * 100

Larger IO sizes tend to be more effected by crossings.

Some enviroments which I've gone onto, the customer has asked whether I could align their partition because it wasn't originally done, but based on whatever is being written to that particular LUN, it might not be worth the hassle, as there may be no gain, and setting the alignment on an existing LUN in Windows for example...well you can't, you'd have to make a new LUN.

However for a brand new partition and LUN, I can't see any reason not to set the alignment.

The Flare 26 paper had some extra bits explained on the section discussing alignment, not in the Flare 28 or 29 papers (i know you have CX4 but you may find this interesting to read).

If you can't find the Flare 26 paper, let me know and I can email that to you.