From what I have heard you cannot change the read and write cache allocation on these boxes. With that said, in the FAQ section of the ax4 support site (link below) there is a section called "How do I enable the cache on the storage system?" Here are the steps to follow, maybe the allocation is there.

1. Open Navisphere Express.

2. Click View > Components.

3. Check the current state of the cache.

www.emc.com/ax45support

For fun I used the navicli command getcache (navicli -h x.x.x.x getcache) to an array in the lab and it produced this:

System Buffer (spA): 592 MB
System Buffer (spB): 592 MB
SPA Read Cache Size = 75
SPB Read Cache Size = 75
SPA Write Cache Size = 356
SPB Write Cache Size = 356

Each SP has 1GB of memory. Bet this cannot be changed.

when I do View - Components I can see disks, Storage processors, power, but nothing like cache.
When I click on SP there are I/O modul but it is N/A?!

everything is green and looks ok, we reboot that box few times, so i think write cache should be enabled, but where I can see that?
I will try this command getcache.
ryan thank you for your help.

then I will assume that cache is enabled
i have only navisphere express and when I run getcache command i get some "agent not privileged .." error, with navicli and navicescli it is the same.

thanks anyway, your posts was very helpfull.

I'm willing to bet if you run spcollect and dig into the created log files you will find it somewhere in there.