Yeah although at least that 846E1 is the old 3Gbps version; I wouldn't recommend it. 24 drives on 4 x 3Gbps = 12Gbps, not really a lot for modern drives.
The 826be26 is the 12-drive version of the 6Gbps, I believe, and that would be a sweet unit. The downside there is the 1k28 power supply ... it is just way too big.
So you are kind of looking at the right things. But you don't understand how it attaches. Great. That is easily rectified.
;-)
The M1015 is not an "8 port". It is a two port. See, look. Count them. Two. Two SFF8087's. Which are four lanes. Which you COULD use as one lane per disk. Which is what you're thinking of, but it is kind of non-elegant.
With SAS, you can connect a quad-lane cable (SFF8087) from your controller to your expander. The cheapest way to get an expander is a chassis that has one built-in, IMO. This gives you a 24Gbps (4 x 6Gbps) pathway from the controller to the expander. Now the trick is, you DO NOT NEED 1 CHANNEL PER DRIVE. The four channels are sufficient to support many drives, and the controller and expander will manage this for you without any effort on your part. However, as you increase the number of drives, you could find yourself limited. So figure 12 drives that can do 150MBytes/sec = 1800MBytes/sec = about 16Gbps. So 12 drives is the sweet spot for a SFF8087 - there should be minimal-to-no contention. If you stick 24 drives on, then you COULD be pulling about 32Gbps at full blast, which would not work. In practice you can't pull that anyways
So the thing is, if you get a 12 drive chassis and fill it, then need more space, you get ANOTHER chassis and just hook that second chassis up to the second SFF8087 on the M1015. You need some different cabling (SFF8088 external stuff) but the idea is the same.
Now the one odd thing is that you might be tempted to get a 16- or 24-drive chassis. If you think you'll need it, I think it is better to just do it and live with the possibility that you'll run into bus contention. Because I don't *think* it'll happen, and if it does, it can probably be tuned-around.
And if it comforts you any, know that my most recent FreeNAS box was a SC846BE26-R920B, 24 drive. I only have 12 drives in it. I speculated that I might someday need to expand to 24. 11 4TB drives in RAIDZ3 gives ~30TB of usable space. Very pleasant. But realistically I am guessing by the time I fill it, I'll be upgrading the drives not adding more.
Now the thing is, you often see people in the forum trying to cobble together some 24-port RAID controller (~$1200 all by itself) or combine a M1015 ($100) with a 24-port SAS expander ($300) and then still having to buy a 24-port Norco chassis ($400) and power supply ($100) and by the time you're all done screwing around you're past $1000. The 846 can be had for like $1200 new, and if you surf eBay a few weeks you can often score one for $400-$500 (possibly a slightly different configuration). Seems to me like the way to go.
