[OmniOS-discuss] Direct SAS or Expander?

[Saso Kiselkov]

On 8/19/16 1:02 AM, Bob Friesenhahn 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.
> 
> Bob

Direct. SATA SSDs and SAS drives on the same expander is asking for
trouble. I've got experiences with locked up expanders, requiring a hard
power cycle of the enclosure. Avoid like the plague.

-- 
Saso