El martes, 19 de septiembre de 2017 21:33:31 (CEST) Andrei Borzenkov escribió: > 19.09.2017 14:49, Senén Vidal Blanco пишет: > > Perfect!! Just what I was looking for. > > Sorry for the delay, because before doing so, I preferred to test to see > > if it actually worked. > > > > I have a doubt. The system works perfectly, but at the time of deleting > > the > > writing disk and merging the data on the read-only disk I fail to > > understand the process. > > > > I have tried to remove the seed bit on disk A and delete the write B as > > you > > mention, and so move the data to A, but tells me that disk B does not > > exist. These are the orders I have made: > > > > md127-> A > > md126-> B > > > > btrfstune -S 0 /dev /md127 > > mount /dev/md127 /mnt (I mount this disk since the md126 gives error) > > btrfs device delete /dev/md126 /mnt > > ERROR: error removing device '/dev/md126': No such file or directory > > > > Another thing I've tried is to remove disk B without removing the seed > > bit, > > but it gives me the error: > > > > ERROR: error removing device '/dev/md126': unable to remove the only > > writeable device. > > > > Any ideas about it? > > Yes, sorry about it. Clearing seed flag on device invalidates > filesystem. What you can do, is to rotate devices. I.e. remove > /dev/md126, set seed flag on md127 and add md126 back. > > I actually tested it and it works for me. >
OK thanks
Now I see how it works :))
With the commands:
mount /dev/md126 /mnt
btrfs device remove /dev/md127 /mnt
We remove the read-only array (A) from the BTRFS system and in doing so pass
all the information from (A) to (B) read-write to mix them.
From what I see is not bad since both (A) and (B) are still operational. (A)
with last year and (B) with everything current.
Finally with this other commands:
btrfstune -S 1 /dev/md126
mount /dev/md126 /mnt
btrfs device add -f /dev/md127 /mnt
we activate the seed bit in md126 (B) and add the (A) in read-write mode,
where the new files will be archived and (B) as store until the following year
and (A) do clean to fill in it new data.
I have tried to rotate twice to see if it goes well and smoothly.
Just comment that I see two small problems to this:
1. The transfer of data from (A) to (B) when removing the read-only disk takes
quite a while and more the more it has stored in the history. It would be nice
if the process were reversed, since in (B) there are fewer "data" stored.
Also, I could not use it monthly or daily for this reason.
2. My idea was to have a larger A-disk than B where I would save the
historical ones, because so in B I could put a smaller disk and something
faster. If the decoupling process outside read-write rather than read-only and
passed the data to A would be ideal for this case.
On the other hand, as an anecdote only, and perhaps for lack of experience or
knowledge, I have used the entire linux system in BTRFS (@ and @home) format
and a single partition md126 to have the system bootable and running simply by
attaching the disk to the computer in degraded mode (swap outside the raid ,
which I'm not so bad: P). This has made that by rotating disks A and B I have
had some problems with grub and fstab at boot, which I had to overcome by
making changes to the boot configurations and some more botches.
I'm going to see a couple more things and if there's any way I can combine
this with snapshots and see if the bulb will light up. If I do not get it I
will try with the other filesystems that you have suggested to me. Although
honestly, I like BTRFS more than the other alternatives, I already use BTRFS
on 5 computers and it goes very well.
Greetings.
> > Thank you very much for the reply.
> > Greetings.
> >
> > El martes, 12 de septiembre de 2017 6:34:15 (CEST) Andrei Borzenkov
escribió:
> >> 11.09.2017 21:17, Senén Vidal Blanco пишет:
> >>> I am trying to implement a system that stores the data in a unit (A)
> >>> with
> >>> BTRFS format that is untouchable and that future files and folders
> >>> created
> >>> or modified are stored in another physical unit (B) with BTRFS format.
> >>> Each year the new files will be moved to store A and start over.
> >>>
> >>> The idea is that a duplicate of disk A can be made to keep it in a safe
> >>> place and that the files stored there can not be modified until the
> >>> mixture of (A) and (B) is made.
> >>
> >> This can probably be achieved using seed device. Mark original device as
> >> seed and all changes will go to another writable device, similar to
> >> overlay; then remove seed bit from original device, "btrfs device remove
> >> writable" device and it should relocate its content back. Rinse and
> >> repeat.
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