Special configuration -- md raid1 root filesystem is on XFS. I know this isn't formally supported, but I've been running RHEL and CentOS this way since the RedHat 7.2 days. And have many machines deployed and tested with this configuration.<br />
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As of CentOS 5.9, kernel 2.6.18-348.el5, a reboot of the system results in a hang immediately after printing:<br />
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"md: md1 switched to read-only mode"<br />
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After 120 seconds, a traceback is produced. I can provide the traceback later if it would be helpful.<br />
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It's important to note that:<br />
* Same hardware, kickstarted with same configuration -- CentOS 5.8 does not hang on reboot.<br />
* Same hardware, kickstarted with same configuration -- CentOS 5.9 and downgraded kernel to 2.6.18-308.el5 does NOT hang on reboot.<br />
* Same hardware, kickstarted with same configuration -- CentOS 5.[678] and upgraded kernel to 2.6.18-348.el5 hangs on reboot.<br />
* Same hardware, kickstarted with same configuration -- CentOS 5.9 using ext3 for root fs does not hang on reboot.<br />
* Same hardware, kickstarted with same configuration -- CentOS 5.9 using ext3 for root fs, and a XFS data partition (md and non-md) does not hang on reboot.<br />
* Same hardware, kickstarted with same configuration -- CentOS 5.9 and NO md raid1, does NOT hang on reboot<br />
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I suspect something changed between kernel level 308 and 348 to interfere with XFS and md raid1 on the root filesystem.<br />
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Looking at the changelog for the 348 kernel, I do see mention of a FREEZE/THAW change and this could have irritated XFS. And perhaps a few other suspicious changes that could also impact XFS. But I'm not sure.<br />
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Any insight as to the cause is appreciated. I can stay at 5.8 for now, but this seems like a potentially serious regression (albeit an edge case) that shouldn't go unreported, either here or upstream.
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