What are the modern-day concerns with using SATA drives behind a SAS expander?

[kuloch]

I'm building a NAS server and would appreciate clarification on some seemingly vague or potentially controversial details (leaving me a bit confused, after most of a couple months frequently reading up on various guides, common mistakes, build recommendations, etc.). I'm splitting these into separate threads to keep each discussion limited in scope. The other question is regarding use of non-SAS drives in a SAS-oriented chassis.

What are the modern-day concerns with using SATA drives behind a SAS expander?

It seems stupid to add yet another post to what is already a long line of discussion threads on this, but to be honest the discussions seem inconclusive to an outsider just now trying to "catch up" on about a decade worth of information (and often misinformation).

The 2015 thread SAS Expanders links to several other sources, some of which point out intermittent issues with using SATA drives over SAS expanders but with some indication this may be a dwindling problem (which was posted over 7 years ago), while other discussions have people claiming they've used SATA behind SAS expanders for years with no issues. Granted, I'll likely be buying largely used gear from datacenter cast-offs (probably aiming for SAS2 HBA+backplane and SATA III drives), so conversations about equipment from 7 years ago may still be relevant to my projected build. So I'm trying to get a feel for what realistic options I have - what to rule out entirely, what to avoid, what to prefer, etc.

Rather than yet another dedicated thread, I'll add a related follow-up question:

Assuming there are still concerns related to "mixing" SATA and SAS drives:
At what point does "mixing" SATA and SAS drives become a concern?

Discussions don't go into much detail but seem to presume the same SAS expander. So which of the below have concerns?

1. SAS HBA mini-quad-port to:
   • 1 expander with both SAS drives and SATA drives
2. SAS HBA with:
   • 1st mini-quad-port => expander 1 with SAS drives
   • 2nd mini-quad-port => expander 2 with SATA drives
3. SAS HBA mini-quad-port to:
   • expander 1 with SATA drives and uplink to:
     • expander 2 with SAS drives

 

[jgreco]

There are probably some specific problems with specific drive models versus particular combinations of parts. It's rare these days. It was really more of a problem in the early SAS days and/or with 1.5Gbps and 3Gbps SATA HDD's.

The thing you're missing here is that the people who were having problems were ALSO buying 5-to-7 year old equipment, i.e. stuff sold from 2008-2010, when SAS1 was still king and SAS2 was brand new. It is likely lots of problems came from that.

At the end of the day, there are no promises. Take care to test your stuff before deploying. Use solnet-array-test to validate that everything seems happy. Don't buy ridiculously old crap, stick to 6Gbps SATA and 6Gbps SAS.

 

[Ericloewe]

To @jgreco's point, you'll find that the likes of Dell, HPE, Supermicro, et al. all sell servers with SATA disks attached to SAS controllers, many via SAS expanders. This is expected to work and any issues are typically outliers.