I've got an older machine (HP DL180 G6) using an HP SmartArray controller (model P410) with 12 drives connected to it. I was not all that interested in the controller's functions, as I wanted to set up a ZFS array, but I found out too late the controller had no passthrough mode.
As a workaround, I created 12 logical "RAID 0" volumes – one for each drive. This setup has worked well for about 3 years now.
The controller has started to show signs of failure, so I want to take this opportunity to move to a plain old SATA HBA now that the funds are available.
After swapping out the the controller for the HBA, will I need to take other steps to have my drives readable, or will it "just work"? (In other words: Did the SmartArray do anything to the data structures that would render the data unreadable to something else?)
Best Answer
For a DL180 G6, you have a couple of options:
Continue to use your multiple RAID 0 arrays - The problem with this is that a drive failure is essentially a Logical Drive failure, and would probably require a reboot to recognize a replacement disk.
Upgrade to a Smart Array P420 or H220 or H240. The P420 can be placed in "HBA mode". The H220 and H240 are HBAs (LSI chipsets). This will give you the raw disk access you're asking for.
Screw it and just make a hardware RAID array of the level you desire (RAID 1+0), create a small logical drive for your OS (sda) and another large logical drive that can be consumed by your zpool. This gives you ZFS volume management and flexibility, but hardware RAID, easy drive replacement, monitoring and a flash/battery-backed write cache.
People on the internet will say "no, don't do this... ZFS wants raw disks", but in reality, this maximizes your disk space because you don't need to allocate OS disks. HP hardware RAID is very resilient. Write cache is nice to have. ZFS is really best suited for the flexibility and performance enhancements of lz4 compression and ARC/L2ARC. If you're not in a position to have proper ZIL SLOG devices and a really well architected setup, the ZFS purist raw disk thing isn't as crucial.