zfs hang in zio->io_cv) with dd read

Ivan Voras ivoras at freebsd.org
Thu Oct 7 12:35:29 UTC 2010

On 10/07/10 14:15, John Hay wrote:
> Hi,
> I got hold of a SunFire X4500 with 48 X 500G disks and thought to try
> FreeBSD 8-stable with zfs on it.
> I have setup the two boot disks in a zfs mirror and then the rest in
> a pool of 6 X raidz2 of 7 disks each.
> I have created a 10G file with dd in the second pool, but if I try to read
> it with dd, dd will hang in "zio->io_cv)" according to ^T. This happens
> everytime. The first time I saw messages about an interrupt storm, so I
> have put "hw.intr_storm_threshold=10000" in /etc/sysctl.conf. According to
> "systat -vm 1" there is atapci for 2-3 seconds and then it is quiet.

There are two things you could try: 1) use the AHCI driver 
(ahci_load="YES" in /boot/loader.conf) and 2) disable superpages, they 
don't get along on a few models of Opterons (vm.pmap.pg_ps_enabled=0 in 

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