IO fluctuation

Steffen Neubauer stefreak at
Sat Aug 21 18:29:08 UTC 2010

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

         NAME                                            STATE     READ 
         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  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 

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...


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