ZFS Re: A specific example of a disk i/o problem

Thomas Backman serenity at exscape.org
Tue Oct 6 06:56:56 UTC 2009

On Oct 5, 2009, at 6:05 PM, Dieter wrote:

> In message <E316139E-FFCF-432F-8DCE-62B120C38E55 at exscape.org>,  
> Thomas Backman writes:
>> I run 8.0-RC1/amd64 with ZFS on an A64 3200+ with 2GB RAM and an old
>> 80GB 7200rpm disk.
>> My problem is that I get completely unacceptable latency on console  
>> IO
>> (both via SSH and serial console) when the system is performing disk
>> IO. The worst case I've noticed yet was when I tried copying a core
>> dump from a lzjb compressed ZFS file system to a gzip-9 compressed
>> one, to compare the file size/compression ratio. screen(1) took at
>> LEAST ten seconds - probably a bit more - I'm not exaggerating here -
>> to switch to another window, and an "ls" in an empty directory also
>> about 5-10 seconds.
> You might find the "RELENG_7 heavy disk = system crawls" thread  
> interesting:
> } I didn't actually solve it or do anything.
> } I just upgraded to RELENG_8.
> }
> } Now it's behaving more like FreeBSD should.
> } I can do sequential reads/writes and still
> } use kbd/mouse/X11/buildworld and so on.

Doesn't really help much I'm afraid, since 8.0-RC1 = RELENG_8 = stable/ 
8. Been running current/stable-8 since May.


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