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SoftRAID Volumes
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Topic starter
Hi folks,
I am upgrading my computer network a bit, and I want to shift from running JBODs locally to a network server for my active files (not just for backups).
I use a Mac Mini (2014) for my network server. It currently has High Sierra on it, but I can upgrade to Mojave.
I'm moving to a 10GbE network, and will plug a TB2 to 10GbE adapter into one of the TB ports on the Mac Mini to get it running at that speed.That leaves me with a single TB2 port on my server machine.
I have two Akitio Thunderbay2 Quads and a single Akitio Thunderbay Duo that I have been using as JBODs at this point, but I am thinking that I can use SoftRAID to set up a RAID 5 or RAID 6 (when available, soon maybe?) with my boxes. What I need is a little help figuring out what I can practically achieve for speed so that I'm not wasting time/money on drives to speed things up without any real benefit.
First, note that the Mac Mini only has a single TB2 controller, and I will be using it for a network connection plus the drives connection!
As I see it, I have two reasonable options:
1. Set up a RAID 5 with 4 drives on one of the Quad boxes. Set up some large drives in the second as backup for that, and then not use the third.
2. Set up a RAID 5 with 8 drives across both Quad boxes. Set up two large drives in the third as backups.
If I set up a 4-drive RAID 5, I expect I should be able to get close to the speed ratings listed in the SoftRAID information. If I set up an 8-drive RAID 5, I suspect that I will be capping out the TB controller in the computer, but I'm not sure by how much. Is it possible to get most of the speed predicted with an 8-drive RAID 5 with that arrangement?
TB2 is rated for 20Gb/sec, and the 4-drive RAID 5 comes in at about 4.5 Gb/sec per the speed sheet, (double that for the network throughput to about 9 Gb/sec). It appears there should be plenty of capacity on the controller to handle at least a 50% increase in speed, maybe more.
Practically speaking, what should I expect to be able to get in my scenario?
This, of course, determines what size drives I need to get, etc. so that's why I'm asking before I decide which way to go.
Thanks,
---Michael
Posted : 23/01/2020 6:02 pm
There is another variable, CPU speed for RAID 5. On the Mini, RAID 5 writes will be slower, as the CPU is not capable of keeping up with the disk requirements.
I would stick with 4 drive RAID 5 volumes, for simplicity. You will have no bandwidth issues with the disks. (Expect 350-450MBs on reads, maybe 20% less on writes Faster drives can get 450-550MB/s)
With 8 disks, you should get close to double that. The TB2 bus can handle about 1.4GB/s. Keep in mind CPU limitations, which are also in play with ethernet. (Traffic is managed by the CPU)
The main problem with 8 drive RAID 5 with two enclosures is the number of parts, that reduces overall safety of your data.
Posted : 27/01/2020 2:07 pm
Topic starter
OK thanks... I hadn't thought about the CPU part, because I was thinking that wouldn't be an issue.
I've decided to move to a new Mac Mini with 10GbE so my initial question isn't really applicable anymore. It will handle all the tasks better with a faster CPU (and double the cores), but I have also decided to go with a 4-drive RAID. Once I have the parts in place, I'll get it started and do some testing.
If I get this running with the Existing Mac MIni, will I have to rebuild the RAID once I get the new one with 10GbE? It is a special order and will take a few weeks to get from Apple.
Posted : 27/01/2020 4:20 pm
No, just move the disks over and they will work. Just use "uninstall SoftRAID" on the old mini when you are done with it, so you can use the license on the new Mini.
Posted : 27/01/2020 7:28 pm
