Dear all: If a btrfs device is missing, the command tool tells user the devid of the missing devices. I understand that each device (disk) in a btrfs volume has been assigned a uuid (UUID_SUB field in udevadm info output). If the device is missing, it's hard to tell user to input such uuid string in command line. So devid is for convenience. In our product, we want to record all disk information of a volume in a file. If a disk is missing, not because it's broken, but because the user has so many disks and in some cases they may put back the wrong one. In this scenario, we can provide the disk information (such as serial number) to user and help them to check if they did something wrong. My question is: is the devid just an alias to sub uuid? for a given disk device, it is never changed during any btrfs operation, including add, remove, balance and replace? or it may be changed, and when? One more question just for curiosity. I checked the source code of btrfs-progs briefly. It seems that there is no data structure in superblock recording all sub-uuids or all devids for the volume, so how does btrfs figure out the missing devid? since they are not always sequential integers, for example, after one device is removed, the devid is simply removed and the devid of other device is not re-numbered. matianfu -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
