Questions about JBOD shelf, ZFS and so on

[Nipp]

Hi team!

I guess the HBA forum is the closest one to ask this.
I have a Synology RS with an expansion unit and I was quite happy with it. But lately, I picked up a great deal on R620 with 384Gb RAM to offload resource-intensive containers from NAS. That worked quite well, so it made me think - the NAS is just storage now. Quite an expensive one and with no options to expand. And with that much RAM on Dell, it seems I would be better off with ZFS on something directly attached to R620.
The trouble is, I don't know much about the directly attached storage. I tried to research, but that area is not the easiest for newcomers. So here is what I want to know and I would greatly appreciate it if you can help me or point me in the right direction in my research.

• HBA and connection to JBOD shelf: How does HBA connect to an enclosure? Is it a single SFF8088 cable connection? I am looking at Dell PowerVault MD1200 as an example. It has 4 SFF8088 ports. 2 "In" and 2 "Out". The "Out" part, as I understand is for daisy-chaining multiple enclosures. And if has two controllers for the redundancy. Do I connect both to an HBA? Is it only a failover or is there more to it?
  
  
• SAS2 vs SAS3: Does it make sense to pursue 12Gb SAS? The storage is mostly cold-ish. Large sequential write and sequential reads, most of the time. How much of a bottleneck will it be for 16-32 drives, 10Tb and 14Tb SATA?
• Enclosures: The PowerVault/PERC 810H appears to be the official solution. There are plenty of NetApp DS4246 on eBay. I wonder if that might be a better option. Also, I wonder if it makes sense to pursue high density and look for 48 or 60 drives enclosures or if it makes sense to stick with something, that won't be sitting half-empty for the foreseeable future?

Thank you.

 

[ericloewe]

How does HBA connect to an enclosure? Is it a single SFF8088 cable connection?

Pretty much. Although using two is conceptually possible, either for increased bandwidth or for multipath, that adds complexity that is often pointless.

And if has two controllers for the redundancy. Do I connect both to an HBA? Is it only a failover or is there more to it?

This is going to depend on the specific unit.

SAS2 vs SAS3: Does it make sense to pursue 12Gb SAS? The storage is mostly cold-ish. Large sequential write and sequential reads, most of the time. How much of a bottleneck will it be for 16-32 drives, 10Tb and 14Tb SATA?

The SAS2 stuff is getting old, but if it works, no reason to avoid it. As for bandwidth, the math is fairly simple. Do you need more than 4x 6 Gb/s for your disks? It's going to depend on the disks and workload. Spinning rust? Not likely to make a practical difference. SSDs? Absolutely.

 

[Bert]

Does dell MD1200 enclosure work seamlessly with regular SAS cards? I had used dell hb 1235 enclosures and they were great. Is it same here or do we need custom sas card etc? Does MD1200 work with SATA drives?

 

[audiophonicz]

Does dell MD1200 enclosure work seamlessly with regular SAS cards? I had used dell hb 1235 enclosures and they were great. Is it same here or do we need custom sas card etc? Does MD1200 work with SATA drives?

Yes they work with SAS cards. Dell cards are usually LSI rebrands, so depending on what you mean by "regular"...
Yes they work with SATA drives.

 

[Bert]

Yes they work with SAS cards. Dell cards are usually LSI rebrands, so depending on what you mean by "regular"...
Yes they work with SATA drives.

Thanks. I got 2 of them for a pretty low price