Write performance

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Write performance

Postby lundman » Sun Nov 04, 2018 9:21 pm

So we sped up the unlinking a bit before, lets take a look at write performance. First I need to try to replicate what people experience so I can if I make it better,

So I have an ancient MacBookPro, and plugged in an Intel 300G SSD to it. Writing the same 1GB file, to 100 files gives me:

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ZFS:
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HFS:
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Looks like we can match HFS quite often, but ZFS has a lot of variation, highest at 45s.

Is this what people means when we talk about "poor performance" ? Is write speed the worst? Or read speed? Listing?
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Re: Write performance

Postby jawbroken » Tue Nov 06, 2018 3:27 am

Thanks for looking into it. This is going to be frustratingly vague, but I think I have more trouble with what I think of as read performance than write. But it's not a straightforward issue, because my scrub performance is very good (e.g. ~80 MB/s per drive). It's more a vague feeling that things are slow, like listing files in a directory (often Finder will just spin for a long time on first access before showing the file list), seeking in a video file (sometimes immediate, sometimes a long period of buffering), things like that. I have another vague feeling that ARC isn't quite working right, also, because I don't seem to get a great hit rate (I seem to recall a better hit rate with Zevo with a similar setup and workload) and I think some people on the forums report improved performance from lowering their ARC size. Sometimes situations just seem counterintuitive, e.g. I'm scrubbing my pool at the moment and streaming video to the Air Video HD app on my iPad seems to be working better than when I am not scrubbing. Not sure if this is at all helpful, I know if the problem was simple you probably would have found it by now.
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Re: Write performance

Postby lundman » Tue Nov 06, 2018 4:06 pm

Is that the consensus? Should focus on read performance over write? Or any other for that matter.
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Re: Write performance

Postby tangles » Thu Nov 08, 2018 3:09 am

Hi Lundy,

Thank you so much for focusing your time on this.
Personally, I'm happy for anyone to tackle either.
Is it at all possible you can start your investigation using multiple vdevs as well?
I'm willing to donate the cash so you can have identical external Firewire/eSata drives for testing. (maybe 3 to include raidz testing)
I have an old MacPro 1,1 I can donate to you if you want it, but as you know, it can't run anything past macOS 10.11 (using bootloader hack)
Alternatively, if you have a static IP, I'm happy to punch a whole through my router if you want ssh access to some test boxes.

I also use a Kanex Thunderbolt to eSATA adapter with laptops to connect disks as it it PM capable.
https://www.apple.com/shop/product/HGC8 ... 30-adapter

Just yell out Lundy if you do want some more hardware… that I can help you with no probs.
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Re: Write performance

Postby lundman » Thu Nov 08, 2018 6:14 pm

Cheers, always appreciated. The patreon donations are high enough that I will buy a thunderbolt something so I can do some high performance testing. Disks and SSDs are not a problem, I just never had a great way to attach them (while avoiding USB). Thunderbolt things don't appear available in Japan, so I'll get something from the states.

I'd be curious in testing the #666 hack test, since it affects writes, and reads, and would in fact be worse for multiple vdev. Although, admittedly it doesn't fix the actual problem, but perhaps alleviates some of it in the IO path. I will need to clean up the hack, so it's nicer, and maybe you can give it a test, to see if it is worth looking it at, or not.

I used to have a macpro1,1, loved that machine, currently have a 4,1 at home. At work I have a trashcan, but obviously it sucks to dev on the machine you test on - maybe i should pick up a 2nd hand mac to do real testing. VMs are great for dev, terrible for performance troubleshooting.

Oh hey, thunderbolt to esata? That changes everything!
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Re: Write performance

Postby lundman » Wed Nov 14, 2018 1:23 am

For those that can, try branch "avoid_alloc" to see if IO is a bit more level
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Re: Write performance

Postby tangles » Tue Nov 27, 2018 11:08 pm

Hey Lundy,

what's the commands to get the avoid_alloc build?

do I gitclone or use zfsadmin?

Happy to test a before and after on the same hardware for you if you like...
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Re: Write performance

Postby lundman » Wed Nov 28, 2018 6:41 pm

With git, you would check it out:

git clone http://github.com/openzfsonosx/spl.git
cd spl
./autogen.sh
./configure
make

cd ../
git clone http://github.com/openzfsonosx/zfs.git
cd zfs
git checkout avoid_alloc
./autogen.sh
./configure
make
./load.sh

I can probably make you a pkg if that is easier, although, if you know how to build master, you'll always be able to run the latest :)
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Re: Write performance

Postby tangles » Thu Nov 29, 2018 12:38 am

okay,

So before I pull down the latest, do you have a test in mind that we should use for consistency?

Those tests you carried out with lots of small files to = nGB versus few large files that also = nGB sounds like a winner to me.

Perhaps it's time to set a new benchmark wiki page? I don't think I'll be selling my 2012 MacPro any time soon.
I also have a 2013 MacPro that I could use but sadly Apple may end its life in a couple of years also. :cry:
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