This is a great thread and clarified a few things I've suspected about these 3U and 4U systems. I wanted to chime in (and subscribe!) with some additional facts I've read (and partially experienced).
Let me discuss the Supermicro 24-bay chassises, specifically the SC846E1 variant. (E16 variant already has the SAS2 backplane, so if you can get one of the E16 models cheap - DO IT!).
SAS - > SAS2
The SAS1 backplane on the older Supermicro SC846E1 models (part number SAS-846EL) can support up to 4TB (maybe 6TB), but only up to 4 drives total. Once you exceed 4 drives though, anything larger than 2TB drives are not recognized. I suspect this is because of the single-port expander, which a single port is actually 4 SAS/SATA ports in that single cable and the expander just does a straight pass through - then it's up to your IBM/LSI/Adaptec controller to support the large drives. But once you install more than 4 drives, the Expander in the backplane takes over, and the SAS (non-SAS2) firmware doesn't support anything larger than 2TB.
^- per Supermicro tech support and other accounts I've read only.
You want the SAS2 backplanes, Supermicro part number SAS2-846EL to be exact for the 24-bay SC846E1 chassis. Be careful when looking at any 24-bay Supermicro chassis though. "E16" means SAS2, "E1" is SAS1.
The SAS2 backplanes support 4TB (and maybe larger) drives, in expanded mode. They also support higher bandwidth (6Gbps/550 MB/s) per port as well, for you SSD guys.
There may be a little concern about these drive Expanders with 16 to 24 drives loaded up... On a single 4-port SFF-8087 cable with a SAS2 Backplane, that's a max bandwidth of 24Gbps, or about 2200 MB/s, which is pretty damn fast for our little home server needs. The SAS1 in contrast is only 1100 MB/s max bandwidth.
This is a different story with "L2" backplane modes (see below).
Supermicro SC846E1 vs SC846E16 variants
In short, the "E1" is the SAS1 3 Gbps version, and the "E16" is the newer SAS2 6 Gbps version.
But, you can pick up the older E1 versions and upgrade the backplane usually pretty cheap if you want for a deal on the SAS2 part number I posted above.
SAS2-846EL1 vs SAS2-846EL2
Note the "L1" vs "L2". It was already mentioned in this thread that some backplanes have two Expanders instead of one Expander chips. That is correct, and you can look for the "L1" and "L2" designation on the backplane to know.
L1 = One Expander chip
L2 = Two Expander chips
They offer these two-chip solutions for one main reason (also already mentioned in this thread):
* Redundancy in case the first Expander fails, the 2nd one automatically takes over. This is in the operating manuals for the backplanes.
Now, there is some very limited information in that it does
bandwidth splitting across the L2 systems. I haven't gotten clarification for that; but again, we don't need more thatn 2.2 TB/s for our home servers (which the SAS2 L1 units are).
Spindown w/IBM M1015 - passthrough, no Expanders
Spindown... In my original WHS I built in 2008, I had all 10 drives spinning down. Since I moved to my IBM M1015s, flashed to LSI firmware, I haven't noticed any drives spinning down. I am still running a few 7 year old 1 TB HDDs, spinning at all times for a few years now.
Has anyone been able to get their drives to spin down? The StableBit DrivePool software I use says they can issue the command; but, it can be ignored by the controllers.
While everything seems fine, and I don't miss the "5-8 second delay" I used to have for drives spinning up, the amount of heat generated in my current 14-drive system is a lot more than I would like (not to mention the power consumption).
IBM M1015 - 2x SFF-8087 "Firmware" / Flash / IT Mode
These are the super-cheap LSI 6Gbps SATA3 controller cards that were mentioned in this thread. I picked up two for $90 total on eBay almost 2 years ago, flashed them to the LSI firmware, and have been enjoying up to 500MB/s from my SSDs connected to them.
http://www.servethehome.com/ibm-m1015-part-1-started-lsi-92208i/
^- that's the great article that explains everything.
Most of these Supermicro chassis though already include a card. But...
The SFF-8087 Controller Card Included in SAS1 chassis
Be careful when getting an older chassis that you plan on upgrading the backplane (see below for backplane upgrades). If it is a non-SAS2 chassis (just SAS), then most likely the controller card that comes with it is only 3Gbps (280 MB/s) per port. Some you can flash to get 4 TB drives recognized, but see previous notes about the SAS1 expander firmware that does not.
What I've seen in Supermicro's tech specs, and all the units on eBay for sale (I've been searching for months) is that if it has a SAS2 backplane, then it has a 6 Gbps controller.
Otherwise, plan on getting one of the IBM M1015s mentioned above, flash it to the LSI IT mode, and be done.
SAS2, on the cheap (as of July 2015)
Me? I've found out that you can upgrade the older chassis to use the newer SAS2 backplanes (though it voids Supermicro's warranty). Let's look at how what this would cost:
* Supermicro Superchassis SC846E1 24-bay SAS1 chassis: $150-$250 on eBay
* Supermicro SAS2-846EL1 Backplane: $150
Looking to be $300 to $400. Most of the time I've seen these for around $250 for the chassis and $300 for the backplane, which is $500+. But setup a price alert and sometimes those chassis come in cheaper as well as the SAS2 backplanes (I got mine for $150 shipped).
The original deal in this thread is awesome - a 16bay, fully functional server with SAS2 and quiet 1200W PSUs. I've been waiting since April for more to pop up, but they haven't. Boo.
I am currently in talks with some local vendors about sourcing an older SC846E1 with a failing backplane (cause I already have the SAS2 backplane to replace it) and no PSUs (so I can use my own).
Replace the PSUs, with any ATX or even the 900W Platinum
Oh, that's another note... You can just drop the PSUs and housing all together and a standard ATX will fit in nice.
Are You Looking For A Less Expensive Norco 4220 / 4224 Alternative? - AVS Forum | Home Theater Discussions And Reviews
In addition, you don't have to go out looking for the 1200W PSUs - some won't even fit. See this reddit thread for good details about replacing them with 900W Platinum units which are very quiet:
Supermicro PWS-920P-1R
Replacement Power Supplies for Supermicro SC846E1-R900B Chassis : homelab
Plex Media Server (PMS)
Those of you that plan on running Plex (and you really should try it) may be very interested in these cheap LGA1366 Xeon mobos/cpus that come in these 3U 16 bay and 4U 24 bay older servers. Most of the cheap $90 quad core Xeon CPUs you'll find in these auctions for another $100 actually have a CPU PassMark of over 7000 or even 8000. That's on par with an Intel 980X Hex core. What does the CPU PassMark mean? It means more
concurrent multiple streams. I've been running into this issue since I setup my extended family on my Plex server. I've seen up to 9 streams at once.
What I am getting at is don't dump those cheap Xeons if you do pick up one of the complete systems.
Ok, that's my first post here...