Richard Scobie wrote:

Or use dumb LSI SAS controllers (sas3442e-r with IT firmware loaded, 
$200) and port expander based chassis that allow considerable 
flexibility regarding md RAID and number of SAS/SATA drives attached.

The problem then becomes choosing the port expander chassis...
I know nothing about this topic :-(
Does the brand/model make difference in performance or reliability?
Do you have any recommendation? Even just one "known good"...
(These chassis are also quite expensive for what I can see.)

Up to 24 and maybe even 48 drives you can find monolithic solutions (one 
chassis for mainboard and disks), but then not many brands make 16-24 
ports controllers. LSI does not seem to make them, am I correct?

Also in a monolithic storage you only have to check that the controller 
declares compatibility with the drives (sometimes there are indeed 
issues) while for port-replicator based storage I don't know if I should 
check the Compatibility List for drives against controllers, or for 
drives against port replicator, or for controller against port 
replicator...?