Resilver keeps restarting

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Resilver keeps restarting

Postby jojo45 » Sat Apr 15, 2017 12:29 pm

I made a pool and then attached a second drive to convert it to a mirror.

It began resilvering immediately, but it keeps on restarting. It gets up to 8% then restarts over and over.

"zpool status" shows that the start time for the resilver keeps going up each time the resilver restarts.

Is there a fix for this?
Last edited by jojo45 on Mon Apr 17, 2017 5:29 pm, edited 1 time in total.
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Re: Resilver keeps restarting

Postby jojo45 » Mon Apr 17, 2017 5:22 pm

I"ve gotten around this by copying data to an external drive, destroying the problematic pool, remaking the zpool by constructing the mirror off the bat rather than attaching a second hard drive, and then copying the data over again.

My concern is that when one of the hard drives fail, resilver is not going to work and I will have to repeat this process rather than relying on zfs to rebuild the mirror.

Has anyone had this problem before?
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Re: Resilver keeps restarting

Postby tangent » Wed Apr 19, 2017 12:30 pm

jojo45 wrote:"zpool status" shows that the start time for the resilver keeps going up each time the resilver restarts.


Yes, but did the amount of work to do reset as well? I mean if it does 8% per restart, it might have just taken 13 restarts to resilver the pool.

I'm not saying that is what happened, I just want to know if you ruled that out before giving up.

My concern is that when one of the hard drives fail, resilver is not going to work


If "zpool scrub" goes through the pool without reporting errors, I'd say it's fine.

If it does report errors, that's probably why the initial conversion of a single-disk pool to a mirror failed: you have some hardware error, and shouldn't be relying on ZFS to save you from bad hardware.

I once used ZFS on a drive in a dodgy USB enclosure, and got megs and megs of errors as a result. Only the fact that the second drive in the mirror was in a much higher-quality enclosure was I able to save that pool from marking files bad due to both copies being unreadable. (That was a temporary measure to rescue a pool, not something I'd do normally.)

ZFS tries its best to save you from bad hardware, but there's a continuum between "good hardware that is failing" and "hardware that is actively trying to sabotage your data."
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Re: Resilver keeps restarting

Postby jojo45 » Thu Apr 20, 2017 8:23 pm

Yes, I checked on that. The amount of work done resilvering reset as well.

It seems I am the only one who has had this problem.

Oh well. It is good enough for me. I send the filesystems to a OmniOS server for archival backup and can always restore from there if need be.

Thank you for your response and your suggestions.
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Re: Resilver keeps restarting

Postby RobRehnmark » Mon Oct 23, 2017 6:01 am

I am having this problem now too.
It's a RaidZ2 that had a drive fail.
I had trouble replacing the drive since I kept getting the response "no such device in pool" or something similar.
It finally accepted the replacement and started resilvering.
After taking a looong time (speed kept going very low a lot of the time) it finally finished.
But it still said the pool was DEGRADED and in the process of replacing.
Then I exported (-f) and imported the pool at which point it started resilvering again. :evil:

If someone has some answers or ideas I'm more than glad to hear them.
Super grateful to the people developing OpenZFS on OS X!
RaidZ2 working well for storing my data, OS X Server share for Time Machine, FCPX, iTunes, Photos, etc. on my Hackinstosh.
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Re: Resilver keeps restarting

Postby e8vww » Thu Dec 07, 2017 10:36 pm

tangent wrote:I once used ZFS on a drive in a dodgy USB enclosure, and got megs and megs of errors as a result.


I have never heard of this, was it the power source or the interface that was causing errors do you think?
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Re: Resilver keeps restarting

Postby tangent » Mon Dec 18, 2017 1:40 pm

e8vww wrote:
tangent wrote:I once used ZFS on a drive in a dodgy USB enclosure, and got megs and megs of errors as a result.


I have never heard of this, was it the power source or the interface that was causing errors do you think?

Does it really matter? Let's think through the cases:

1. The enclosure electronics were the problem and the external power brick was fine. Solution: you toss the cheap electronics and get a better enclosure, which comes with its own power brick, so you might as well toss the old brick as well unless you've got some other use for it.

2. The brick is the problem, so you spend about as much on an aftermarket power brick as you spent on the enclosure, because you're trying to avoid underspending and getting the same problem. You might as well have replaced both pieces at once.

My purpose in using ZFS is not to let me get away with cheaping out on electronics. Unfortunately, that's hard to avoid in the USB world because China has convinced everyone that you can get a five-star enclosure for under $20. The problem is, those rating 5 stars would either not know an enclosure worth five stars if they saw one, or they'd see the price tag and rate it 1 star for "bad value."

I've never had a USB hub that's been problem-free, for example. Ports die, you have to occasionally unplug and re-plug everything, etc. We didn't tolerate that in the SCSI days, but then, we were spending $100 on cables, so we didn't have to put up with it. Now when you get an enclosure, cable, and power supply for $13.64 — not to mention the 20 years of inflation — if it fails we just shrug and say, "Well, what did you expect?"

The Thunderbolt market seems to be protected from this race to the bottom syndrome for now. Here's hoping that it remains a "high end" feature, from the PC world's perspective. It's what we used to call "normal."
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Re: Resilver keeps restarting

Postby FadingIntoBlue » Mon Dec 18, 2017 9:42 pm

I've got a nice little extreme example of USB vs Thunderbolt, though I'm sure there are other factors influencing things.

2104 Mac Mini - lowest specs 1.4GHz 4GB memory, but booted off an external Thunderbolt SSD
Thunderbolt 2 4 Disk 2 way Mirror 4TB + Mirror 3TB pool vs USB 3.0 8TB Single Disk Pool

The former works perfectly adequately as a media pool for iTunes, reasonable r/w performance for that job
The latter when employed for the same function sticks on reads and writes, corrupts copies, and generally complains so much that it is reformatted to a backup HFS+ drive

I'm surprised the former works as well as it does, given the very low RAM it has to work with. I had hopes for the latter, after having no joy at all with USB 2 in any configuration I've ever tried.

I think the financial premium for Thunderbolt is well worth the saving in my time and energy (and I was a bit of a SCSI wizard back in the day :)
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