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SubjectRe: raid1 with nbd member hangs MD on SLES10 and RHEL5
On 6/14/07, Paul Clements <> wrote:
> Mike Snitzer wrote:
> > Here are the steps to reproduce reliably on SLES10 SP1:
> > 1) establish a raid1 mirror (md0) using one local member (sdc1) and
> > one remote member (nbd0)
> > 2) power off the remote machine, whereby severing nbd0's connection
> > 3) perform IO to the filesystem that is on the md0 device to enduce
> > the MD layer to mark the nbd device as "faulty"
> > 4) cat /proc/mdstat hangs, sysrq trace was collected
> That's working as designed. NBD works over TCP. You're going to have to
> wait for TCP to time out before an error occurs. Until then I/O will hang.

With (uni-processor) I've not seen NBD hang in the
kernel like I am with RHEL5 and SLES10. This hang (tcp timeout) is
indefinite oh RHEL5 and ~5min on SLES10.

Should/can I be playing with TCP timeout values? Why was this not a
concern with; I was able to "feel" the nbd
connection break immediately; no MD superblock update hangs, no
longwinded (or indefinite) TCP timeout.

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