Moving ZFS to a Dell Perc H310 HBA

A friend of mine gave me a Dell Perc H310 HBA nearly half a year ago which was flashed to IT-mode, which basically removes all the fancy RAID functionality from the card and turns it into a dumb HBA, just showing all the disks to the operating system. A good guide to flashing Dell Perc cards can be found on https://fohdeesha.com/docs/perc.html.

That very same website lists some reasons why you’d want to flash to IT mode:

There’s two main reasons to do this, assuming you don’t need the hardware RAID functionalities of the stock firmware:

Better Performance: the plain LSI IT firmware in this guide drastically increases the max queue depth of the adapter. For instance on the H310 Mini, it goes from 25 with the stock Dell RAID firmware to 600 with the LSI IT firmware. This can mean drastic improvements in IOPS with heavy SSD configurations for example.

Different Driver: The stock Dell firmware (MegaRAID-based) uses the MegaRAID driver in Linux/FreeBSD/etc. In some distributions this can cause issues, for example FreeNAS has issues pulling SMART data from drives connected to a MegaRAID controller. After crossflashing to IT mode, the card is used by the OS via the much simpler mpt3sas driver.

For ZFS you don’t want all the fancy stuff in the firmware of the card - the filesystem will handle everything for you.

So I finally got round to buying some SAS to SATA breakout cables (amazon url - SAS 36P SFF-8087 to 4 SATA), and switching over was as easy as replugging the cables and booting up the system.

Net effects? A few watts more power usage, and faster I/O - or atleast it feels faster, I didn’t do any proper benchmarks before. But the 6 rust drives in 3 mirrors + 2 SSD’s is more than enough to blow through the bandwidth cap the builtin C236 has.