IO fluctuation

[Jason Leschnik]

http://forums.freebsd.org/showthread.php?t=17036&

This is a good starting point, there is also some good info using certain
tools to force the drives to not goto spindown sleep.


On Sun, Aug 22, 2010 at 4:29 AM, Steffen Neubauer <stefreak at stefreak.de>wrote:

> Hello Claudiu :)
>
> Sorry that I didn't answer these obvious questions in my first post.
>
> Am 21.08.2010 20:16, schrieb claudiu vasadi:
>
>  How did you setup your drives in ZFS ? stripe ?
>>
>
> raidz1 .... Here is my zpool status output:
>
> # zpool status
>  pool: tank
>  state: ONLINE
>  scrub: none requested
> config:
>
>        NAME                                            STATE     READ WRITE
> CKSUM
>        tank                                            ONLINE       0     0
>     0
>          raidz1                                        ONLINE       0     0
>     0
>            gptid/7b91a9b4-ab05-11df-8c6e-001d7d004144  ONLINE       0     0
>     0
>            gptid/7cebaf7b-ab05-11df-8c6e-001d7d004144  ONLINE       0     0
>     0
>            gptid/7e43d7a2-ab05-11df-8c6e-001d7d004144  ONLINE       0     0
>     0
>
> errors: No known data errors
>
>
>  what bsd version do you have and what platform ?
>>
>
> # uname -a
> FreeBSD tank 8.1-RELEASE FreeBSD 8.1-RELEASE #0: Mon Jul 19 02:36:49 UTC
> 2010     root at mason.cse.buffalo.edu:/usr/obj/usr/src/sys/GENERIC  amd64
>
>
>
>  Do you see this big fluctuation when copying some big file like say and
>> iso
>> or movie ?
>>
>
> Both, on small filesystem access and when copying big files.
> When I'm listening to music with VLC over NFS it stalls regularly.
> When I'm working on the shell the commands block randomly for a certain
> time.
>
> But I get that fluctuation on raw device access, too, look:
>
> # dd if=/dev/ad0 of=/dev/zero bs=1M
> ^C0+0 records in
> 0+0 records out
> 0 bytes transferred in 9.848682 secs (0 bytes/sec)
> # dd if=/dev/ad0 of=/dev/zero bs=1M
> ^C1056+0 records in
> 1056+0 records out
> 1107296256 bytes transferred in 9.492375 secs (116651130 bytes/sec)
>
> So this is not a zfs problem. But I don't think it's the hardware, too - I
> used that mainboard before FreeBSD with no problems.
> And the WD EARS drives can't be the problem on raw device access, too,
> because I used bs=1M, that should be enough...
>
> This is really strange...
>
> Greetings,
> Steffen
>
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-- 
Regards,
Jason Leschnik.

Mob. 0432 35 4224
Uni mail. jml974 at uow.edu.au
Work mail. jll at ansto.gov.au