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BTRFS scrub speed is insanely slow.
So I have a RN104, with about 10TB of disk space. When I set it to do a BTRFS scrub, the speed is horrific. I'm getting something like 30GB/hour of scrub speed. At the present rate, it would take ...
I haven't reproduce your issue on my RN104 yet. The speed is 138MB/s. I want to fill more data in my box and try again. Do you mind change your WD drive and try again?
scrub status for 4814067b-f1a9-4dc2-afb2-99879e706058
scrub started at Fri Feb 17 04:05:24 2017, running for 01:01:51
total bytes scrubbed: 500.25GiB with 0 errors
scrub status for 4814067b-f1a9-4dc2-afb2-99879e706058
scrub started at Fri Feb 17 04:05:24 2017, running for 01:01:56
total bytes scrubbed: 500.86GiB with 0 errors
scrub status for 4814067b-f1a9-4dc2-afb2-99879e706058
scrub started at Fri Feb 17 04:05:24 2017, running for 02:22:16
total bytes scrubbed: 1.13TiB with 0 errors
scrub status for 4814067b-f1a9-4dc2-afb2-99879e706058
scrub started at Fri Feb 17 04:05:24 2017, running for 02:22:21
total bytes scrubbed: 1.13TiB with 0 errors
Those numbers look very much in line with what I would expect, in fact a bit better than I would expect.
I'm ordering a new drive to replace the WD Green, and then we'll see. It will likely take me almost a week to get the new drive in, get the RAID rebuilt, and then do the test, so stay tuned.
Before you replace the disk I would suggest that you make sure that your backup is up to date.
Definitely wise. I've got everything backed up, pulled the green today and replaced with a helium filled WD Red 8TB, should be considerably better than the 3TB seagates I have alongside it.
The RAID is rebuilding, should take about a day, then I'll redo the scrub and see if it behaves any better. The green is still checking out as healthy, so not sure what I expect. Would be a bit surprised if this solved the problem. Probably still a bug either way. If the green is so bad as to slow things to a crawl, the system should be detecting that something is wrong, and I also would have expected it to affect (for instance) the RAID scrub as well.
Anyway, we'll see soon.
glad to hear that the situation evolve!!
Disk is swapped, rebuild and reshape are done. Then I ran the scrub, and here's what I've got.
root@readyNAS:~# btrfs scrub status /data
scrub status for bfb437e8-16ee-444c-b4c8-48cee4f845e1
scrub started at Sat Feb 25 01:37:29 2017, running for 07:34:32
total bytes scrubbed: 60.08GiB with 0 errors
That's about 10 GB/hour. To do the whole ~4TB of data would therefore take roughly 400 hours, or about 20 days. This is pretty much the same as before.
This result isn't surprising, since we know it's not a hardware problem, because it was introdued by a software update.
Is there anyone at Netgear who can attempt to fix this bug?
It's a hell of a mess you are into!!!!
Good luck and patience!!
Cheers!
Yeah, thanks.
The problem isn't devastating, because the NAS works just fine in every other way. I can even literally read every byte off it, and thus accomplish the scrub, in a reasonable amount of time. It's just the scrub functionality itself that is totally broken.
I guess let's see if Netgear tries to figure out a fix.
joey123you are learning the hard way and learning fast!!!!
In front of those kinds of mess I fell like a complete moron (excuse my French and I am a Frog as you noticed the way I slaughter the Cheakspear language!):)!!!
joey123 wrote:
root@readyNAS:~# btrfs scrub status /data
scrub status for bfb437e8-16ee-444c-b4c8-48cee4f845e1
scrub started at Sat Feb 25 01:37:29 2017, running for 07:34:32
total bytes scrubbed: 60.08GiB with 0 errors
That's about 10 GB/hour. To do the whole ~4TB of data would therefore take roughly 400 hours, or about 20 days. This is pretty much the same as before.
FWIW I just did a scrub on an RN52x NAS with 3x8TB disks in RAID-5. The volume has about 8.5 TiB of data on it. It was run from the web ui, so it was the btrfs scrub + raid scrub combination. The disks are all WD80EFZX.
The scrub took 31 hours. I didn't check CPU utilitization while it was running though.
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