Btrfs Gets RAID 5/6 Fixes With Linux 4.12

[Zan Lynx]

I'm telling you that if you hook up 4 SATA SSDs to an el cheapo small NAS box from 2012, the SATA controller does NOT have enough bandwidth to drive that at RAID 0. And because of the stupid designs for lane sharing on at least one box, SATA bandwidth would DROP whenever you started using Ethernet or USB 3.

[caligula]

I'm telling you that if you hook up 4 SATA SSDs to an el cheapo small NAS box from 2012, the SATA controller does NOT have enough bandwidth to drive that at RAID 0. And because of the stupid designs for lane sharing on at least one box, SATA bandwidth would DROP whenever you started using Ethernet or USB 3.

Probably on a cheap NAS box from 2012, but how is that relevant today? I mentioned the cheap boxes as a real alternative that people buy. They're not buying those to achieve maximum perf, they just want something that works OOB with decent performance and for them, that seems decent enough.

If you're seriously considering an alternative for Ryzen, there are plenty of choices. I can give several reasons why a dedicated NAS box might make sense: 1) you can better optimize the CPU and the PSU for the load and save energy, thus money 2) if you only need gigabit LAN, Avotons / APUs and similar NAS CPUs are most probably fast enough for you. 3) aforementioned boards and CPUs come with more SATA slots for your disks (and 2-3 GBLAN + IPMI) 4) there are several NAS distros for you prebuilt for such dedicated machines 5) the NAS boxes have nice removable disk slots for hotplugging new disks. These "real computers" have no issues saturating GBLAN, heck even $20 Orange Pi PC 2 can do that with three RAID-0 disks connected via USB/SATA adapters.

[Stellarwind]

Exactly. Raid 1 and 10 are safe. I'm using raid1 on my server and raid10 on my desktop. AND I also keep backups.

Except that it "Can get stuck in irreversible read-only mode if only one device is present." ... but if your drives never fail and you don't try to mount them rw when one is offline, they are safe... maybe.

[Zan Lynx]

Except that it "Can get stuck in irreversible read-only mode if only one device is present." ... but if your drives never fail and you don't try to mount them rw when one is offline, they are safe... maybe.

I've had drives fail in my btrfs array. I recovered just fine. Now, I do remember that when it failed I was up to four drives using RAID 1, so btrfs continued happily in read/write mode.

But if you have two drives in RAID 1 and one fails what do you expect it to do? It has to become read-only because you no longer have a mirror to write to.

If you wanted to keep going at that point you'd rebalance the array to "single", then you could keep using it. Or you could add a temporary device like a USB stick or external drive.

[Zucca]

Except that it "Can get stuck in irreversible read-only mode if only one device is present." ... but if your drives never fail and you don't try to mount them rw when one is offline, they are safe... maybe.

My arrays contain 4 and 6 disks. I've also pulled disks out before (accidentaly) I issued proper commands to remove a drive from the pool (basically simulation of a sudden drive fail). Not bit lost on those occasions. I've also been battling with hibernate and suspend failures. Some filesystem errors have poped up, but btrfs has always managed to fix them all (scrub).
I keep at least three drives in my btrfs pools, so I doubt I'll ever come across that ro situation.

But as always, no matter what filesystem you use - backups are important. Although I don't actually remember when I last needed to return something from backups, since snapshots cover most human errors.

Lastly YMMV.

[stiiixy]

This article WAS about BTRFS RAID 5/6 becoming useful.....poopoo on your other RAIDs!

[Zucca]

Oh. Poopoo us for going way too off topic.

[aht0]

I'm telling you that if you hook up 4 SATA SSDs to an el cheapo small NAS box from 2012, the SATA controller does NOT have enough bandwidth to drive that at RAID 0. And because of the stupid designs for lane sharing on at least one box, SATA bandwidth would DROP whenever you started using Ethernet or USB 3.

Long before SATA bandwith becomes an issue in situation you described, gigabit link coming out of the NAS gets saturated. 2012 means SATA 3 (it appeared past 2009). Which means 6Gbit/s. You can perhaps guess the max. throughput of single gigabit Ethernet link. It's a moot issue, even if the NAS box comes with dual links and you trunk them together..

Now, could we get back to track talking about BtrFS?

[Zan Lynx]

Long before SATA bandwith becomes an issue in situation you described, gigabit link coming out of the NAS gets saturated. 2012 means SATA 3 (it appeared past 2009). Which means 6Gbit/s. You can perhaps guess the max. throughput of single gigabit Ethernet link. It's a moot issue, even if the NAS box comes with dual links and you trunk them together..

Now, could we get back to track talking about BtrFS?

I'm not stopping you. The whole thing was in response to Caligula talking about how Ryzen is overkill for NAS, and I don't agree with that. Small CPUs don't have enough bandwidth to scrub BTRFS or ZFS and talk at the same time, let alone chew bubblegum.

[Zucca]

I'm not stopping you. The whole thing was in response to Caligula talking about how Ryzen is overkill for NAS, and I don't agree with that. Small CPUs don't have enough bandwidth to scrub BTRFS or ZFS and talk at the same time, let alone chew bubblegum.

On my FX-8350 I see ~20-30% total load when scrubbing. All disks are SSDs. So. Ryzen might be a bit overkill, but if going with R7 1700, you'd also have almost 50% less of heat generation to deal with.