Performance issues with 1.8.1 on High Sierra

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Performance issues with 1.8.1 on High Sierra

Postby kpbowman » Tue Jan 08, 2019 8:21 am

As a newbie to the group I apologize if this has been covered before, but I have not found any discussion elsewhere.

We are using ZFS with single disk drives to make an offline backup copy of a large data(~300 TB) set that we have on a FreeNAS RAID. Previously we successfully copied ~120 TB to ~30 4-TB drives. We copy the data to the drive with rsync and then the scrub the volume to verify it.

Since updating to 1.8.1 performance has decreased dramatically. Copies are slower, the scrub is slower, and the entire Mac suffers stalls of 10 to 30 seconds during which no applications respond. Sorry, I don't remember which version we upgraded from (1.6 or 1.7 I expect).

Hardware: Late 2015 iMac, 4 GHz Core i7, 32 GB RAM, external OWC USB3 drive toaster.
Software: High Sierra, 10.13.6.

Memory usage is high (18 - 20 GB wired), but memory pressure does not seem to be a problem.

I am considering downgrading to an earlier version. Before I do that, does anyone have other suggestions?

Thanks, Ken
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Re: Performance issues with 1.8.1 on High Sierra

Postby Sharko » Tue Jan 08, 2019 12:57 pm

I'm not super expert on 1.8.1, having just moved to this revision myself, but in general when I've experienced non-responsive behavior it seems to have come down to RAM starvation, regardless of what Activity Monitor is reporting. So perhaps a first step would be to try limiting the amount of RAM that ZFS is allowed to allocate for the ARC, following the instructions on https://openzfsonosx.org/wiki/Memory_utilization . For what it is worth, in my recent testing of 1.8.1 (1.8.2) on El Capitan with RAM limited to 8GB I have not seen any stalls whatsoever.
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Re: Performance issues with 1.8.1 on High Sierra

Postby lundman » Tue Jan 08, 2019 5:20 pm

I'm still trying to get someone to try the avoid_alloc branch to see if it helps
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Re: Performance issues with 1.8.1 on High Sierra

Postby kpbowman » Fri Feb 01, 2019 12:32 pm

Reducing the memory usage to 8 GB seems to have solved the problems that we were having. When I get a chance, I will try reducing it to 4 GB and see if that changes anything.

I am a scientist, not a system software developer, so I don't know what the implications are. Can a better means of automatically selecting the memory limit be implemented? Or as a simple solution, can the default be set to a lower value?

Thanks for the help, Ken
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Re: Performance issues with 1.8.1 on High Sierra

Postby mkush » Wed Feb 20, 2019 10:51 am

lundman wrote:I'm still trying to get someone to try the avoid_alloc branch to see if it helps


I think I was the first one to document this behavior being fixed by a low ARC value. I’m more than willing to test. Please tell me how.
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Re: Performance issues with 1.8.1 on High Sierra

Postby lundman » Thu Feb 21, 2019 4:28 pm

If you are able to compile master and try it - that would be great, there are improvements in master already. Then if you get that far, we can also try the extra branch, to see if it gets additional improvements.

https://openzfsonosx.org/wiki/Install#I ... rom_source

Otherwise, we'll have a Mojave .pkg out soon for people to try.
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Re: Performance issues with 1.8.1 on High Sierra

Postby mkush » Fri Feb 22, 2019 8:31 am

OK... not set up to build at the moment but if I get bored I may try. Otherwise the package sounds like a plan.
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