Date: Mon, 11 May 2015 18:56:15 +0200 From: Gabor Pali <pgj@FreeBSD.org> To: freebsd-fs@freebsd.org Subject: mksnap_ffs: Cannot create snapshot: File too large Message-ID: <CAHnG2CzeimP=Ay-JpTomEE_YJmBNYJdharbMiNrGT8=EWAzhDQ@mail.gmail.com>
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[Please, cc me in your replies as I am not subscribed to this list. Thanks!] Folks, Recently, I started to use the snapshot feature of UFS, but I have been experiencing some oddities with it that puzzles me. I have a FreeBSD/amd64 10.1-RELEASE system (on a Hyper-V-managed VM), and I have a relatively small, about 8 GB of size, partition with UFS2, SU enabled where I want to take snapshots. It is mounted fine and works fine, but sometimes (quite at random), when the mksnap_ffs(8) utility is invoked, it gives the following error message (and creates an empty snapshot file, without the "snapshot" system flag set). # mount | fgrep /mnt/foo /dev/da2a on /mnt/foo (ufs, local, noatime, soft-updates) /mnt/foo on /some/other/directory (nullfs, local) /mnt/foo on /yet/another/directory (nullfs, local, read-only) # cd /mnt/foo # /sbin/mksnap_ffs .snapshot mksnap_ffs: Cannot create snapshot .snapshot: File too large In the meantime, I see the following messages in dmesg(8): bad block 3327649050063220270, ino 263776 pid 60313 (mksnap_ffs), uid 0 inumber 263776 on /mnt/foo: bad block While sometimes, the very same command on the very same file system works as expected. Could this be due to the additional nullfs(5) mounts? What does the "bad block" refer to? By the way, I also observed that once the snapshot is created successfully, its date still keeps changing. What does that mean? I did not find any information about that neither in the respective man page nor in the Handbook. It may be also related that I remove the snapshot file (via rm(1)) and recreate it under the same name (with mksnap_ffs(8)) in 30-minute intervals (from a cron(8)), that is when I use the updated snapshots to do a backup from the file system. Comments, hints, and ideas are welcome.
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