Anand Jain posted on Mon, 14 Sep 2015 17:44:25 +0800 as excerpted: > Hi Qu, > >> Unfortunately, single mode means no duplication. >> And degrade mount only works for RAID level with >> duplication(DUP,RAID1/5/6/10). > > further to the below commit. > > commit 95669976bd7d30ae265db938ecb46a6b7f8cb893 > Btrfs: don't consider the missing device when allocating new chunks > > in case of 2-disk RAID1 mounted with only one good disk, we would create > Single profile and actually the created single profiles are still > workable with one disk failed. And so the proposed patch below will let > single profile to be mount in this context.. > [PATCH 23/23] Btrfs: allow -o rw,degraded for single group profile > > to recover when missing disk is replaced balance convert can migrate > single profiles back to RAID1 profile. > > Also your explanation for degraded is correct, I am ok to use a new new > mount option (like auto-reduced-profile ?) if needed / confusing. > > Any comments / feedbacks are welcome.
I'm familiar with the issue, and for all I know it works exactly as described, but if so, shouldn't it be changed so that while 2-device raid1 mounted with only a single device create single-profile chunks only for data, metadata chunk-creation will default back to dup-profile? If there's a good reason it doesn't, could someone explain it? It seems to me that raid1 already indicates that two copies is wanted, so if it's operating degraded with only a single device, shouldn't it go dup, particularly for metadata? (If possible, I'd say for data as well, but that's not possible except in mixed-bg-mode.) -- Duncan - List replies preferred. No HTML msgs. "Every nonfree program has a lord, a master -- and if you use the program, he is your master." Richard Stallman -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
