On Monday December 15, jnelson-linux-raid@xxxxxxxxxxx wrote: > According to the manpage for mdadm, --write-mostly can only be used > add build, create, or add time. How does one set write-mostly devices > *after* they've been added? You cannot. The easiest approach is to remove it and re-add it with the write-mostly flag. > > mdadm /dev/mdX --write-mostly /dev/someDevice > succeeds but does nothing. > > According to Documentation/md.txt, writing writemostly into > /sys/block/mdX/md/dev-someDevice/state > should do it, and it sort of appears to: > > turnip:~ # mdadm --detail /dev/md11 > /dev/md11: ... > Number Major Minor RaidDevice State > 2 43 0 0 active sync /dev/nbd0 > 3 8 0 1 active sync /dev/sda > turnip:~ # echo writemostly > /sys/block/md11/md/dev-nbd0/state > turnip:~ # mdadm --detail /dev/md11 > /dev/md11: .. > Number Major Minor RaidDevice State > 2 43 0 0 active sync writemostly /dev/nbd0 > 3 8 0 1 active sync /dev/sda > turnip:~ # mdadm --examine-bitmap /dev/nbd0 > Filename : /dev/nbd0 > Magic : 6d746962 > Version : 4 > UUID : cf24d099:9e174a79:2a2f6797:dcff1420 > Events : 3840 > Events Cleared : 3840 > State : OK > Chunksize : 4 MB > Daemon : 5s flush period > Write Mode : Normal > Sync Size : 78123988 (74.50 GiB 80.00 GB) > Bitmap : 19074 bits (chunks), 0 dirty (0.0%) > turnip:~ # > > > Why doesn't --examine-bitmap show the right mode? What were you expecting? The bitmap never reports anything about writemostly, only write-behind. > > Also, removing the bitmap from the array does not zero out the bitmap > on the actual device. Shouldn't it do that? No. It simply records in the array metadata that there is no bitmap. It might be sensible to get "--examine-bitmap" to report that the bitmap is not active in some way. NeilBrown > turnip:~ # mdadm --grow /dev/md11 --bitmap=none > turnip:~ # mdadm --examine-bitmap /dev/nbd0 > Filename : /dev/nbd0 > Magic : 6d746962 > Version : 4 > UUID : cf24d099:9e174a79:2a2f6797:dcff1420 > Events : 3841 > Events Cleared : 3841 > State : OK > Chunksize : 4 MB > Daemon : 5s flush period > Write Mode : Normal > Sync Size : 78123988 (74.50 GiB 80.00 GB) > Bitmap : 19074 bits (chunks), 0 dirty (0.0%) > turnip:~ # > > This is with mdadm 2.6.4 on 2.6.25.18-0.2-default > I can try mdadm 3.0 if you like. > > -- > Jon > -- > 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 -- 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
