Wondering if it could be done:
Linux supports with mdadm growing of sw raid arrays. I can`t find it in open-e, there is only feature for adding a spare disk not growing the s/w array with that disk. I could create another RAID group and merge them with volume manager but I will lose space due to parity disk.

Linux supports multipathing (failover, multibus etc.) with FC initiators and dm-multipath. I wonder it could be added as many FC connections are done by fabric using many paths for redundancy and HA.
With DS4800 connected as target to the DSS with two paths I see one DS4800 LUN and one LUN with 0GB with "not supported" label. When I fail one of two redundant controllers drive 0GB disappears. When i unfail this controller, sometimes I get a message from DS4800 that DSS uses wrong path through bad controller, through not preferred path.
I think FC should be realy tuned.

Another my conception is to add a FlashCache support. SSD disks are much faster so caching data from SAS, SATA or FC disks on SSD drives should give a performance jump for performance demanding setups.

When i remove drive from RAID array physicaly with sw raid and again put the disk in I get "part of s/w raid" label and can only clean disk and need to reboot the DSS is bad... I should also have the ability to put this drive again in the same array without manual changes in DSS. Mdadm should support such a thing.

You may say who uses sw raid but using FC disks it is the best and cheapest way to go.

Also think about giving ppl access to root account from SSH with prompt and access to running their Linux commands.

I am really interested in that software so far testing it for two days.