Andy Smith <a...@strugglers.net> writes: > Hi Felix,
hello Andy, thank you for the quick reply! > On Fri, Dec 29, 2023 at 04:46:10PM +0100, Felix Natter wrote: >> I have /dev/md0 mounted at /storage which consists of two HDDs. >> >> Now I would like to add an SSD drive for better performance of >> VMs. Usually, before doing this, I make sure that all of my disks are >> mounted using UUID and not device names. I do not think this is >> the case for the two member HDDs of md0 (cat /proc/mdstat). >> Is there an easy way to fix this? > > What are you trying to fix? Filesystems have a UUID. MD RAID devices > have a UID. And MD RAID member devices also have UUIDs, but they are > all different *kinds* of UUID. Only filesystems have a filesystem > UUID that you use in /etc/fstab and other places. You mount things > by filesystem UUID. You don't mount MD RAID member devices; mdadm > assembles them. > > RAID assembly normally happens automatically by udev finding block > devices that have the same array id as the one that mdadm is trying > to incrementally assemble, until all their member devices are found. > > So what is it that you are actually wanting to do? If you just want > to mount whatever filesystem is on md0 by *filesystem* UUID, you do > that in the normal way as it has nothing to do with MD: you use > blkid or tune2fs or whatever to read the fs label and put that in > /etc/fstab. I was just worried that devices (i.e. /dev/sdx) will change when adding another drive. I understand that Debian's SW-RAID assembly does not refer to disks via device names :) >> If I need to reinstall, can I keep the two member HDDs with all the >> data, i.e. does the Debian12 installer recognize the member HDDs >> and will allow me to configure /dev/md0? > > Yes. When you come to the partitioning and software RAID section of > the installer your existing md0 should already be there. That's very good! > But to be > absolutely sure you may wish to totally ignore md0 and its member > devices during install as all their data and the metadata on their > member devices will still be there after install. You should just > be able to see the assembled array in /proc/mdstat, and then mount > the filesystem from /etc/fstab. Totally ignoring these devices > during install avoids you making a mistake where you alter one of > them. So /dev/md0 will be automatically assembled when I boot the system (cat /proc/mdstat), and I can mount it using UUID? I couldn't do this on another system, where the software raid(1) is for the root filesystem, though. But as I understood you, in the case of the root fs, the above mentioned problem does not occur? Many Thanks and Best Regards, Felix -- Felix Natter
