Scalable home NASScalable setup

[rungekutta]

Hi guys, first time poster so be gentle...

FreeNas looks like a great alternative for my current and future needs but I'd appreciate some feedback on current plans to validate my line of thinking.

Got nearly 2TB of data out of which 1TB is highly precious and irreplaceable. Currently using an appliance NAS of 2TB and backing up on USB disks. Ext3 used everywhere.

I'm starting to run out space so need an alternative, and ZFS and particularly its data resilience features (eg checksum) appeals to me.

Question is what hardware platform would provide more space now and ideally some scalability in the future. Without massive overkill - this is for home use and relatively light at that. After some reading on this forum I'm currently considering a Supermicro build and initial set of 2+1 4TB disks. If and when I need more space in the future I'd add another 2+1 vdev (maybe 8TB disks by then) and add to so the same zpool to expand it.

Next step after that, if relevan, would be to swap out the initial set of 2+1 disks with something larger.

Does this sound like a reasonable approach? If I understand things correctly this setup means I could lose 1 disk in each of the 2 vdevs respectively, but if I have drive failures on the wrong 2 disks at once (ie within the same vdev) I'd lose the entire zpool, correct?

Anything else obvious that I may be missing here?

Thanks!

 

[ethereal]

if you are interested in keeping your data safe i would recommend a raidz2 which need a minimum of 4 disks

 

[rungekutta]

2+2 sounds overkill frankly as I'll be doing backups anyway. Unless I go 6 disks immediately in which case I agree 4+2 probably makes more sense for my needs than 2x (2+1). However my current storage needs are not massive, hence me thinking 2+1 now and another 2+1 down the line (when bigger disks are cheaper) would make more sense. Hmmm...

I guess I could go 6x 2TB now (in 4+2) for same capacity as 2+1 4TB but how would I expand such a setup in the future? Other than adding even more drives (entering different league in terms of chassi / cooling reqs etc) and/or swapping out all 6 for larger ones...?

 

[ethereal]

they don't recommend raidz1 with drives larger than 1tb

 

[ethereal]

you can use raidz2 with 3 hdd but it needs to be configured using the command line

 

[styno]

My recommendation would be to go 4+2 or 6+2 with smaller/cheaper disks and swap them out for bigger when you need the space later (or in case they would break and need to be replaced).

 

[nojohnny101]

definitely should go with nothing less than RAIDz2, this forum generally recommends against RAIDz1 unless yo have unique circumstances. You stated in your original post you have data that is very precious, so going with RAIDz2 is the minimum you should start with.

You could start with 4 X 2tb (or if you can afford, 3tb) and then future expansion would be just replacing the discs with larger capacity, you could do this without having to rebuild your entire pool. Or if you can swing it, a RAIDz2 setup with 6x3tb seems to be the sweet spot for a lot of people on here and is what I'm running. Having 6 disks in your initial vdev would allow a lot of expansion with larger capacity drives in the future and serve all your storage needs for years to come.

Rememebr though, RAIDz is not a backup. If your data is truly previous you'll have a freenas box that is backed up externally, any way you want as long as it is backed up.

 

[danb35]

you can use raidz2 with 3 hdd but it needs to be configured using the command line

...and you might as well just build a three-way mirror then.

@rungekutta, the concern with RAIDZ1 is that when one disk fails, you're left with no redundancy. If you then experience a read error while attempting to resilver (resync) to the replacement disk, the affected data will be lost. If that read error happens to be in a critical piece of metadata (which should be highly unlikely), you may lose the pool. Hard drive capacity today is such that a read error is relatively likely, which is why RAIDZ1 isn't recommended. The concern isn't so much that two disks will die at the same time (though that's also a possibility), but that a read error on one while you have no redundancy can result in data loss.

With that said, I ran my server (a couple of generations back) with 3 x 2 TB disks in RAIDZ1, and had to replace a disk a couple of times. The replacement went perfectly each time. There's a lot about that build I wouldn't recommend, but it did the job at the time.

If I understand things correctly this setup means I could lose 1 disk in each of the 2 vdevs respectively, but if I have drive failures on the wrong 2 disks at once (ie within the same vdev) I'd lose the entire zpool, correct?

That's correct, with the caveat about read errors noted above.

 

[rungekutta]

Thanks very much for the input guys, very helpful. Sounds like 6 (3TB) drives in RAIDZ2 is the way to go. The only thing that pains me with such a setup is I would have to replace all 6 drives in order to grow capacity (short of adding even more drives, with associated consequences (case, cooling, etc)).

Re backup, I currently use external USB-drives and plan to continue to do so. Obviously another full-blown FreeNas installation would be ideal, but a little costly. Redundancy in the NAS itself combined with 2 external drives that I rotate off-site is enough for me. It will get awkward the day I can no longer fit my data on a single physical disk - with that limit currently at 8TB (?) I've got some leeway still.

 

[nojohnny101]

The only thing that pains me with such a setup is I would have to replace all 6 drives in order to grow capacity

That is one of the trade offs of having a 6 disc vdev.

Re backup, I currently use external USB-drives and plan to continue to do so. Obviously another full-blown ReadyNas installation would be ideal, butalittlecostly. Redundancy in the NAS itself combined with 2 external drives that I rotate off-site is enough for me. It will get awkward the day I can no longer fit my data on a single physical disk - with that limit currently at 8TB (?) I've got some leeway still.

That sounds fine, and is the cheapest solution you could go with as you said.

 

[rungekutta]

That sounds fine, and is the cheapest solution you could go with as you said.

Perceived wisdom on this forum seems to be to keep the USB drive non-ZFS (e.g. Ext), attach to another computer and backup over the network? That's how I do it today from my appliance NAS in any case.

 

[Robert Trevellyan]

initial set of 2+1 4TB disks. If and when I need more space in the future I'd add another 2+1 vdev

While RAIDZ1 is not recommended for modern disk capacities, 3 disk RAIDZ1 vdevs are the least-bad RAIDZ1 option.

If you really want to start small and grow gradually, you might consider starting with a mirror and adding one or more mirrors later. It's still not as resilient as RAIDZ2 but it has the benefit of greater flexibility.

If you can get by with 4 disks, at least for the next couple of years, consider a Dell PowerEdge T20 or a Lenovo TS140.