On Thu, February 26, 2009 1:22 am, Chris Webb wrote: > I use md arrays made up of slots synthesized through device mapper from > physical storage distributed across a cluster of machines. When these > slots > are created, they are guaranteed to be zero-initialised, so I can safely > do > mdadm --create --assume-clean to avoid an initial resync. > > When I grow the backing slots, the new storage space is also > zero-initialised, so I'd like to be able to do the equivalent of > mdadm --grow --size=max --assume-clean. However, --assume-clean isn't > supported for grow operations. > > Is there some way I can tell the kernel driver (perhaps through sysfs) > that > the resync is clean/already complete to avoid unnecessary heavy IO on > every > grow? I tried things like > > echo idle >/sys/block/mdX/md/sync_action > > without success. No, there isn't any way do get --grow to --assume-clean. And I cannot immediately think of a neat way to implement it. I'll have a think about it and let you know if I come up with anything. If you want to hack your own kernel, you could just remove the mddev->recovery_cp = mddev->dev_sectors; from raid1_resuze (Assuming it is raid1 arrays that you are growing). Then the resync-after-grow would never happen. Or if you want to be slightly more subtle, remove the if (mddev->pers) return -EBUSY; from resync_start_store. Then before a grow that you want to be --assume-clean, write into /sys/block/mdXX/md/resync_start the number of sectors in the final raid1 array. That last might be the way I end up doing it, but I'm not sure yet. NeilBrown -- 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
