[OmniOS-discuss] Direct SAS or Expander?

[Joshua M. Clulow]

On 18 August 2016 at 16:02, Bob Friesenhahn
<bfriesen at simple.dallas.tx.us> wrote:
> I am looking at a 16-bay SuperMicro chassis.  There is the option of using a
> SAS HBA with 16 channels (e.g. Avago SAS 9300-16i) and no expander or a SAS
> HBA with 4 channels and an expander.  Most drives would be SAS but I might
> want to fit a couple of SATA SSDs.
>
> Is there a strong technical reason (performance, reliability, uptime) to
> prefer one or the other with OmniOS and zfs?
>
> The main technical issue I am already aware of is that one should not put
> SATA devices behind an expander.
>
> I am leaning toward the 16 channels and no expander solution since it feels
> better from a failure-mode standpoint, because it lessens contention, and
> because it should allow use of SATA SSDs.

If it's an option (as it seems to be here), I would always opt for a
system without an expander.  An expander is just another active
component with its own potentially buggy firmware.

Less firmware is essentially a riff on "less moving parts" from a
reliability standpoint.  Also, if you ever need to upgrade the
firmware in the expander, that will likely be extremely difficult or
even impossible.

-- 
Joshua M. Clulow
UNIX Admin/Developer
http://blog.sysmgr.org