Le 15/09/2016 à 23:54, Chris Murphy a écrit : > On Thu, Sep 15, 2016 at 3:48 PM, Alexandre Poux <pums...@gmail.com> wrote: >> Le 15/09/2016 à 18:54, Chris Murphy a écrit : >>> On Thu, Sep 15, 2016 at 10:30 AM, Alexandre Poux <pums...@gmail.com> wrote: >>>> Thank you very much for your answers >>>> >>>> Le 15/09/2016 à 17:38, Chris Murphy a écrit : >>>>> On Thu, Sep 15, 2016 at 1:44 AM, Alexandre Poux <pums...@gmail.com> wrote: >>>>>> Is it possible to do some king of a "btrfs delete missing" on this >>>>>> kind of setup, in order to recover access in rw to my other data, or >>>>>> I must copy all my data on a new partition >>>>> That *should* work :) Except that your file system with 6 drives is >>>>> too full to be shrunk to 5 drives. Btrfs will either refuse, or get >>>>> confused, about how to shrink a nearly full 6 drive volume into 5. >>>>> >>>>> So you'll have to do one of three things: >>>>> >>>>> 1. Add a 2+TB drive, then remove the missing one; OR >>>>> 2. btrfs replace is faster and is raid10 reliable; OR >>>>> 3. Read only scrub to get a file listing of bad files, then remount >>>>> read-write degraded and delete them all. Now you maybe can do a device >>>>> delete missing. But it's still a tight fit, it basically has to >>>>> balance things out to get it to fit on an odd number of drives, it may >>>>> actually not work even though there seems to be enough total space, >>>>> there has to be enough space on FOUR drives. >>>>> >>>> Are you sure you are talking about data in single mode ? >>>> I don't understand why you are talking about raid10, >>>> or the fact that it will have to rebalance everything. >>> Yeah sorry I got confused in that very last sentence. Single, it will >>> find space in 1GiB increments. Of course this fails because that data >>> doesn't exist anymore, but to start the operation it needs to be >>> possible. >> No problem >>>> Moreover, even in degraded mode I cannot mount it in rw >>>> It tells me >>>> "too many missing devices, writeable remount is not allowed" >>>> due to the fact I'm in single mode. >>> Oh you're in that trap. Well now you're stuck. I've had the case where >>> I could mount read write degraded with metadata raid1 and data single, >>> but it was good for only one mount and then I get the same message you >>> get and it was only possible to mount read only. At that point it's >>> totally suck unless you're adept at manipulating the file system with >>> a hex editor... >>> >>> Someone might have a patch somewhere that drops this check and lets >>> too many missing devices to mount anyway... I seem to recall this. >>> It'd be in the archives if it exists. >>> >>> >>> >>>> And as far as as know, btrfs replace and btrfs delete, are not supposed >>>> to work in read only... >>> It doesn't. Must be read write mounted. >>> >>> >>>> I would like to tell him forgot about the missing data, and give me back >>>> my partition. >>> This feature doesn't exist yet. I really want to see this, it'd be >>> great for ceph and gluster if the volume could lose a drive, report >>> all the missing files to the cluster file system, delete the device >>> and the file references, and then the cluster knows that brick doesn't >>> have those files and can replicate them somewhere else or even back to >>> the brick that had them. >>> >> So I found this patch : https://patchwork.kernel.org/patch/7014141/ >> >> Does this seems ok ? > No idea I haven't tried it. > >> So after patching my kernel with it, >> I should be able to mount in rw my partition, and thus, >> I will be able to do a btrfs delete missing >> Which will just forgot about the old disk and everything should be fine >> afterward ? > It will forget about the old disk but it will try to migrate all > metadata and data that was on that disk to the remaining drives; so > until you delete all files that are corrupt, you'll continue to get > corruption messages about them. > >> Is this risky ? or not so much ? > Probably. If you care about the data, mount read only, back up what > you can, then see if you can fix it after that. > >> The scrubing is almost finished, and as I was expecting, I lost no data >> at all. > Well I'd guess the device delete should work then, but I still have no > idea if that patch will let you mount it degraded read-write. Worth a > shot though, it'll save time. > OK, so I found some time to work on it.
I decided to do some tests in a vm (virtualbox) with 3 disks after making an array with 3 disks, metadata in raid1 and data in single, I remove one disk to reproduce my situation. I tried the patch, and, after updated it (nothing fancy), I can indeed mount a degraded partition with data in single. But I can't remove the device : #btrfs device remove missing /mnt ERROR: error removing device 'missing': Input/output error or #btrfs device remove 2 /mnt ERROR: error removing devid 2: Input/output error replace doesn't work either btrfs replace start -B 2 /dev/sdb /mnt BTRFS error (device sda2): btrfs_scrub_dev(<missing disk>, 2, /dev/sdb) failed -12 ERROR: ioctl(DEV_REPLACE_START) failed on "/mnt": Cannot allocate memory, <illegal result value> but scrub works, and I can add and remove an another device if I want. It's just the missing device that I cant get rid of. Any other idea ? -- 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
