Messages in this thread | | | Date | Thu, 14 Jun 2007 21:16:14 -0400 | From | Paul Clements <> | Subject | Re: raid1 with nbd member hangs MD on SLES10 and RHEL5 |
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Mike Snitzer wrote: > On 6/14/07, Paul Clements <paul.clements@steeleye.com> 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 kernel.org 2.6.15.7 (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 kernel.org 2.6.15.7; I was able to "feel" the nbd > connection break immediately; no MD superblock update hangs, no > longwinded (or indefinite) TCP timeout.
I don't know. I've never seen nbd immediately start returning I/O errors. Perhaps something was different about the configuration? If the other other machine rebooted quickly, for instance, you'd get a connection reset, which would kill the nbd connection.
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