Thanks Brett.

I wasn't aware of RaidZ's limitation on adding devices.

A quick scan of the BTRFS documentation shows that it doesn't have the same limitation. However, raid 5 and 6 are still listed as having significant issues with data recovery and should be used for testing purposes only. [1]

Given my plan is to increase capacity by adding, rather than replacing, drives it looks like an mdadm managed raid 5/6 pool might be the better option.

[1] https://btrfs.wiki.kernel.org/index.php/Using_Btrfs_with_Multiple_Devices

On Sat, Dec 6, 2014 at 2:02 PM, Brett Pemberton <brett.pemberton@gmail.com> wrote:

On Sat, Dec 6, 2014 at 9:16 AM, Tim Hamilton <hamilton.tim@gmail.com> wrote:
> I'm in need of a PCIe SATA controller that works well under linux and
> supports BTRFS / ZFS raid arrays to be used in a home NAS I'm building and
> am no sure what I'm looking for.
>
> My current need is only for a single additional SATA port but my preference
> is for a card that will support future expansion

Keep in mind, with ZFS for example, you can't do like mdadm, and just
add a drive to a RAID5/6 array and reshape, growing to use more
devices.

Your best bet is to start off with the maximum number of drives you
plan to use, and upgrade capacities, instead of adding more devices.
Can't comment on BTRFS.

FWIW, I've bought a few of these over the years:
http://www.msy.com.au/vic/pascoevale/peripherals/8896-channel-pes3a-020-pci-e-2-port-sataiii-card.html

Work fine under Linux/FreeBSD. No complaints. Cheap.

/ Brett

Vote NO in referenda.