Dual-port SAS HDD ?

[Ben RUBSON]

> On 6 May 2021, at 15:24, Alan Somers <asomers at freebsd.org> wrote:
> 
> On Thu, May 6, 2021 at 4:52 AM Ben RUBSON <ben.rubson at gmx.com <mailto:ben.rubson at gmx.com>> wrote:
> Hi,
> 
> I'm building a new ZFS pool from scratch, choosing my own hardware etc...
> For sure I'll go for the standard SAS2008 / SAS3008 controller.
> 
> However, I'm wondering whether or not I should absolutely go for dual-port SAS HDD (with dual backplane, controller...).
> I have some difficulties to find enterprise grade dual port SAS HDD.
> HGST used to provide Ultrastar SAS HDD which were dual-port.
> However, strangely, Western Digital does not advertise their Ultrastar DC SAS HDD as bringing dual-port, so I guess they're not.
> 
> Any thoughts / advices regarding this topic ?
> 
> Many thanks for your help,
> 
> Kind regards,
> 
> Ben
> 
> It's just a matter of high availability.  Can you tolerate an outage if a JBOD I/O controller fails?  If so, then you don't need dual-port.  But server crashes are more common than JBOD I/O controller failures.  So you should worry more about that.

Thank you Alan.
Of course you're right, JBOD IO controller is not the first outage cause, and disks themselves are more prone to fail...

I even wonder whether or not dual path is actively used for HDDs, as dual-port ones are rather hard to find...
Not sure then it's really worth it...

Of course feel free if I'm wrong / I missed something / one actively uses it and has some experience / references to share !

Thank you again,

Ben