SAS HBA interoperability with backplanes & enclosures (SGPIO,SFF-8485,IBPI etc.)

[Andy McClements]

Hi, I've come here looking for information to help me integrate a solution using SAS HBA and disk backplanes (for my personal use), which may potentially come from different vendors. Of particular interest are:

Support for OpenBSD 5.9
Full function of RAID status LED's
Support for SES-2

I'm completely new to this area but after a bit of research there seems to be quite a variety of approaches followed by vendors over the last few years. I've seen some solutions which bypass the HBA>backplane, instead using a separate I2C connection. I've seen some other solutions where SGPIO is used, but on a separate header instead of as sideband connections on a SFF-8484. I've seen other solutions which adopt the standard physical connections for SGPIO (eg. via SFF-8484 or 8087), but which implement functionality on the backplane which seem to exceed that provided by IBPI (eg. HP Smartdrive), and which therefore presumably have implemented vendor-specific use permitted by SFF-8485.

I've not yet found much discussion of these issues or reliable information. So any pointers to outside resources or discussion or advice here would be very welcome.

 

[Terry Kennedy]

I've not yet found much discussion of these issues or reliable information. So any pointers to outside resources or discussion or advice here would be very welcome.

You mention a HBA and RAID status LEDs. Normally a HBA (an LSI card in IT mode, for example) doesn't handle RAID - it is left to the operating system (for example, ZFS). So you won't get an LED function for things that aren't physical level error conditions - for example, a ZFS resilver (the equivalent of a RAID drive replace operation) won't do something like blink a LED to indicate the rebuild is in progress).

A generic controller plus a generic non-expander backplane will normally get you 2 LEDS per slot with sidebands, usually with no SES device visible to the operating system. One LED is drive present/activity and the other is the locate/fail LED. An example would be a LSI 9201-16i controller with a Supermicro SAS-836A backplane.

An expander backplane will usually show up as one or more SES devices which handle the fault/locate (and possibly additional) LEDs.

Other than that, you're probably dealing with vendor-specific extensions - for example, the EPCT function on 3Ware controllers which supports 3 or more LEDs on specific (mostly obsolete) backplanes.

If you already have a controller or backplane, you may want to look for something known to be compatible (post model numbers here). Most people here seem to use LSI controllers (or OEM versions of those) an Supermicro chassis and backplanes are also popular here. So that's likely where the greatest amount of expertise will be found.

 

[Andy McClements]

Thanks, I was using the term HBA in a very generic sense. Your comments are very helpful and reassuringly, reflect some of what I've managed to figure out already.

My needs are actually extremely simple, I'm building a low-power two-node server cluster each with a 2-disk mirrored boot/data volume. The hosts have only a single PCIe 1.0 slot and I'm planning to run OpenBSD. Performance and expandability are much less important than robustness and power consumption. The backplane I want to use is a simple 8-slot internal unit with two separate power domains (upcycled from a dead Fujitsu TX200). I'm now planning to acquire a couple of SAS3081E-R, and see if they work for me in IR mode, if not I'll reflash them to IT mode and use sw RAID.