SAS vs SATA performance

[lowlander]

Hi,

We are reviewing a server configuration that is scalable regarding storage. It should be Windows 2019 with ReFS or a XFS system. Regarding pricing there is a huge difference between SAS and SATA storage. For performance purposes we configure the biggest RAID controller with the 8GB cache onboard. What are the pros and cons regarding using SAS vs SATA disks ?

thanks !

[lowlander]

ah. forgot to mention, is there any limit on the size of a repository ? is 300 TiB doable, or should we split this size of repositories split in multiple servers or RAID controllers ?

[Gostev]

I suspect that with spinning disks in a server chassis, interface won't matter all that much, as the bottleneck will be IOPS. But we may want to wait until @tsightler returns from vacation and shares his opinion... he's our guru in this kind of stuff.

But since you also plan on getting an enterprise-grade RAID controller, which is the right thing to do (makes sure it has BBWC) - I believe you will want NL-SAS disks for access to enterprise features like enterprise command queuing and concurrent data channels. SATA interface does not support that. NL-SAS is sort of an "enterprise SATA drive", so it's price should be much closer to SATA rather than to SAS drives.

300TB is right on a border line in my mind, I would not push further at this time especially on XFS. ReFS is currently more proven on such a large volume sizes.

[DonZoomik]

I don't have any hard measurements but my perception with 100TB+ repos is that SATA tends to be slower. One repo was accidentally ordered with SATA drives and it's noticeably slower than SAS-based ones, even with SSD caching.
NL-SAS gets you deeper queues with better prioritization and possibly different firmware algorithms (and multipathing if you can use it). Possibly NL-SAS is a bit more reliable as well (more factory testing? SCSI being a more mature interface?), in my experience (hundreds of disks in JBODs and NASes and SANs), they fail about... half as much - no hard data, just a perception.
Price difference is almost or totally non-existent so I'd recommend SAS.

[tsightler]

I can only re-enforce what was said above, NL-SAS is the best option and should be only marginally more than SATA for the overall solution, if you're seeing some major price difference between NL-SAS and enterprise grade SATA drives, I would suggest investigating further as I'd be concerned that they might not be enterprise grade SATA disks. Now, if you are comparing SATA disks to 10/15K SAS drive indeed those are a LOT more expensive.

NL-SAS and enterprise SATA disks are basically the same hardware/7.2K RPM spinning platters with nothing more than a different controller/interface on them, however, that SAS interface still provides some measurable benefits. The combination of the dual ported interface and the more advanced queuing with SAS will generally squeeze about 15-20% more real-world performance from those spinning platters, and perhaps up to 30% in some workloads. Doesn't sound like much but, since NL-SAS is generally only a very small premium vs enterprise grade SATA disks, it's almost certainly worth it. Also, with larger RAID groups, the dual porting can be quite advantageous as it's completely possible to saturate a single SATA channel during sequential operations when there are lots of disks in a single channel/port.

[nitramd]

I've been very pleased with the performance of NL-SAS. Tom has summed up the technical benefits quite well. I'll second @DonZoomik's expereince.

In short, you get the benefit of large SATA platters with the advanced SAS interface. What's not to like?

Hope this helps and good luck.