Considering options for new SSD's/HDD's, and a SAS controller

[curtii]

Hello, and thanks in advance for any advice!

This post came out very long, so I'm splitting it - First post is an intro, with my specific hardware/situation, and the second post is true to the subject: Looking for advice on specific storage hardware. Thanks for reading!

I tried FreeNAS out a few months back on some leftover hardware, and I liked it a lot. FreeNAS didn't like the hardware, though, so I purchased a base platform to meet the recommendations. After bouncing ideas around in another thread, here's what I ended up building:

Motherboard: Supermicro X10SRi-F
Processor: Xeon E5-1620 v3
Memory: 32gb ECC/RDIMM: Hynix HMA84GR7MFR4N-UH

Due to the expense, I decided to split up the upgrade into manageable chunks - Start with the above listed components and use my old drives until I can afford to upgrade. If it's relevant, My current (dying) pool is 4x Samsung EcoGreen F2 HD154UI HDDs, with 2x Adata ASP600S3-32GM-C SSDs as a mirrored SLOG. Long story short, the HDDs aren't holding up as well as I had hoped, so I'm now looking into replacing them. I've been doing some research, but still having a hard time determining what would be most cost-effective, so I'm hoping some of the awesome people here can weigh in.

Here's the rundown of my workload: Currently only one user, but I run a number of somewhat demanding applications:
I have a bittorrent server running on this pool, since I find that the best way to obtain Ubuntu/Other OS installers. I like to contribute to the open source community where I can, so I let those transfers seed, which generates a nearly constant flow of small reads.
I'm also heavy into cryptocurrency, and currently have about 10 different altcoin wallets running. This, similar to the torrent server, generates a pretty constant flow of small-file storage IO.
Particularly the cryptocurrency work, but also just in general, I plan to continue scaling this out, so I want to make sure I have reasonable room to grow with the pool I setup. Scalability is the main reason I started looking into enterprise grade storage solutions in the first place.
Beyond that, it's basic home use applications: simple streaming movies/music, offloading storage from workstations/laptops, etc.

 

[curtii]

Thanks for bearing with me, that was a long-winded lead into the real point of this thread: The storage hardware I'm currently considering:

SAS controller: LSI 9207-8i - Looks to me like this is the most cost-effective controller, since a 6gbps SAS card should cover me (please correct me if I'm wrong about that)

SATA SSD: Samsung 850 EVO - Cost-effective SSD option. While I'd love to use something like an Intel PCI-e SSD or a Seagate SAS SSD, the cost is just a bit prohibitive.

SAS HDD: Seagate Cheetah 15k - "True" SAS HDD (compared to "Near Line" 7200 RPM SAS drives) have been a bit scarce, but this is one I'm considering that's a good example for the purpose of this discussion.

"Near-Line" SAS HDD: WD RE SAS - From what I've found so far, this seems to be a good balance between the lower cost of SATA drives, and the higher performance/better features of the SAS interface.

WD RED (SATA) - Hoping to figure out something better that's within the budget, but am still considering these for bulk storage of data that I don't need performance/reliability for.

So, those are the pieces (and similar ones) that I'm trying to make a decision on. I know that's all pretty open-ended, but I do have a couple specific questions I'd like to get some input on:

SAS controller + SATA SSD's: Is there a benefit to doing this over using the motherboard's SATA connections? I understand that SAS has benefits like full duplex communication and better queuing/instructions/etc., but I don't know if those benefits are lost when connected to SATA drive(s). I'm pretty sure I will be using at least some new SSD's, so whether or not they'd benefit from being connected via a SAS controller would definitely be useful to know.

SSD's and a lot of writes: Most of what I described for my use case doesn't do much erasing/rewriting data, but is the lower number of write cycles in SSD's something I should be concerned about?

Enterprise-grade 15K SAS HDDs Vs. Consumer grade SATA SSDs: Most of what I've found so far suggests that even when comparing the highest grade HDDs to low-end SSDs, that SSDs still win by a long shot. Does this still hold true in FreeNAS/ZFS environments?

Ultimately, I think I'm likely going to make two pools: One high-performance but low-capacity to stay within my budget, and another that takes advantage of cheaper drives for bulk storage.

 

[Dice]

When looking at SSDs, you might be interested in comparing the durability of the drives. It differs by orders of magnitude.....

LSI 9207-8i

Would work fine.

I think I'm likely going to make two pools: One high-performance but low-capacity to stay within my budget, and another that takes advantage of cheaper drives for bulk storage.

That is very wise.

The true beauty of ZFS is the flexibility it offers while using the same hardware. Another way of putting the performance vs bulk storage idea is to use the same hardware but configured to appropriate needs. Dividing pools up into the performance corner (eats a lot more drives when configured in multiple vdevs of mirrors) and others which might be configured as fairly wide Raidz2 or even Raidz3 units depending on the expansion horizon and upgrade plans. Now the cool thing is that you can change the distribution from multiple mirrors (your performance pool) and putting these into the raidz tank (naturally the opposite cannot be done as easily).

I'm just putting it out there to provoke a thought. SSDs streamlined might be the way to go. But also potentially far less reliably depending on selected model and your write patterns as you indicated...

Imo, the essence of ZFS is the ability to bring high performance out of cheap parts. That should be exploited.