# [OmniOS-discuss] Direct SAS or Expander?

Saso Kiselkov skiselkov.ml at gmail.com
Fri Aug 19 00:05:36 UTC 2016

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    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

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