On Wed, Apr 08, 2009 at 05:50:46PM -0400, Bill Davidsen wrote: > Steven Ellis wrote: >> I've resolved most of my raid issues by re-housing the affected system >> and replacing the motherboard, but across the 3 boards I've tried I >> always have an issue with my /dev/md1 array producing mismatch_count >> of 128 or 256. >> >> System is running Centos 5.2 with a Xen Dom0 kernel >> >> This md1 volume is a pair of 40GB HDs raid1 on an IDE controller which >> I them have a bunch of LVM's that are my Xen guests. >> >> Is there any chance that these mismatch_count values are due to swap >> partitions for the Xen guests? > > That's the cause, and since md code doesn't currently have a clue which > copy is "right" it's always a problem if you do something like suspend > to disk. You probably don't do that with xen images, but swap and raid1 > almost always have a mismatch. But only because (for non-xen guests) the raid1 code and the swap code / data live in the same address space, and could be changed in between the two writes. I would be surprised if this happens for xen guests, where the address space is not shared; once the xen guest initiates a write, dom0 gets the data and writes it from its internal buffer, not the domU's one which could be modified. At least, that's how I think things happen. regards, iustin -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
