-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Hi, Is there any way to willingly write more data to a degraded array? There are other use cases for such a possibility as well. Just think of migrating from software raid (and lvm) based setup.
Thanks, Andreas Philipp On 03.02.2012 20:17, Lutz Euler wrote: > Hi, > > Btrfs seems not to want to allocate new chunks on a degraded mirror, > severely restricting the amount of new data that can be written to such > a filesystem. I hope this is not intentional? It makes mirroring much > less useful than it could be, at least for me. > > My use case: I want to use btrfs with two mirrored disks on a desktop > machine. Lets say the filesystem is far from full. Assume one disk > fails, I send it in for RMA and have to wait 6 weeks for a replacement. > I could live without the mirror redundancy during this time but not > without the ability to store more data on the filesystem. > > I would prefer if btrfs remembered the size of the missing device and > allowed to allocate space on the degraded mirror until the capacity is > reached that the nondegraded mirror had. > > Here is how to reproduce the effect: > > Create and mount a mirror of two 20 GB devices: > > # dd if=/dev/zero of=/tmp/img0 bs=1 count=0 seek=20G > # dd if=/dev/zero of=/tmp/img1 bs=1 count=0 seek=20G > # losetup -f /tmp/img0 > # losetup -f /tmp/img1 > # losetup -a > /dev/loop0: [0802]:1441845 (/tmp/img0) > /dev/loop1: [0802]:1441856 (/tmp/img1) > # mkfs.btrfs -d raid1 -m raid1 /dev/loop0 /dev/loop1 > # mount /dev/loop0 /mnt > # df -h /mnt > Dateisystem Size Used Avail Use% Eingehängt auf > /dev/loop0 40G 56K 38G 1% /mnt > > Umount, make one device unavailable and mount degraded: > > # umount /mnt > # losetup -d /dev/loop1 > # mount -o degraded /dev/loop0 /mnt > # df -h /mnt > Dateisystem Size Used Avail Use% Eingehängt auf > /dev/loop0 40G 312K 2,0G 1% /mnt > > Notice that the "Avail" value has shrunk drastically; it seems > to show only the space available in already allocated chunks. > Now, "df" might simply lie, so let's try to put data on the filesystem: > > # dd if=/dev/zero of=/mnt/data bs=4K count=512K > > -> ENOSPC after writing 1.1 GB > > The software used is: > > Kernel: v3.3-rc1-383-g0a96265 > uname -a: Linux test 3.3.0-rc1 #1 SMP PREEMPT Sun Jan 29 16:06:29 CET > 2012 x86_64 x86_64 x86_64 GNU/Linux > btrfs-progs: cloned on 2012-01-25 from > git://git.kernel.org/pub/scm/linux/kernel/git/mason/btrfs-progs.git, > latest commit is fdb6c0402337d9607c7a39155088eaf033742752. > OS: Ubuntu 11.04. > > Kind regards, > > Lutz > -- > 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 -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.9 (MingW32) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ iQEcBAEBAgAGBQJPW5sMAAoJEIW3W1BiBxU7WaQIAI3BgB5zbfxzMKKyhlEzdjwR 2faI539BuTSz3RVpoCn8BMREVJSvfDcdT40uIV+io53IW5/0AgH8y0Tlg5HTmm5V XtGtbT8MFpnQvSvUoWVJdDiIhlo1BNhL3KBVm5dXHQEkeviQZs1RZ0ndI1IKlnnB gIZEYRJpb9ig9RI2HKlhKRPWDiTSyWBTEL0HuteY7jmISThCGTvnAq1b6A/mSVq6 CQvHnk7h1LbCvBBUvIxUUJewrfdnspqiGR95hAA9RGSQP7iAu7nMmi1rY0vw3cmF +aF6r5eljvwmmdB/msDomaBYgWuf6RBV2aMZvmXigeU/g1tSbWRn3El8dBnqDZM= =xi/2 -----END PGP SIGNATURE----- -- 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
