Date: Mon, 16 Feb 2015 11:47:06 -0500 From: Charles Sprickman <spork@bway.net> To: Konstantin Belousov <kostikbel@gmail.com> Cc: freebsd-fs@freebsd.org, Matthew Seaman <matthew@freebsd.org> Subject: Re: About Filesystem freeze/thaw in freebsd Message-ID: <16F552EF-83A2-496B-A7ED-7B62B78D666B@bway.net> In-Reply-To: <20150216095410.GH34251@kib.kiev.ua> References: <COL128-W74C2CE6B8243E74B26A286F62E0@phx.gbl> <54E1B90E.8050101@freebsd.org> <20150216095410.GH34251@kib.kiev.ua>
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On Feb 16, 2015, at 4:54 AM, Konstantin Belousov <kostikbel@gmail.com> wrote: > On Mon, Feb 16, 2015 at 09:31:58AM +0000, Matthew Seaman wrote: >> On 02/16/15 09:07, zx zx wrote: >>> Hi, I am experimenting to do a live backup of FreeBSD >>> VM. Question is do we have freeze/thaw interfaces in FreeBSD? I >>> searched a lot in web and freebsd source code, just could not find >>> the right interface. As I know that in linux:VxFS >>> provides ioctl interfaces to application programs to freeze and thaw >>> VxFS file systems. The interfaces are VX_FREEZE, VX_FREEZE_ALL, and >>> VX_THAW.About Freeze and thaw Freezing a file system temporarily >>> blocks all I/O operations to a file system and then performs a sync >>> on the file system. Current operations are completed and the file >>> system is synchronized to disk. Freezing a file system is a necessary >>> step for obtaining a stable and consistent image of the file system >>> at the volume level. Consistent volume-level file system images can >>> be obtained and used with a file system snapshot tool. The freeze >>> operation flushes all buffers and pages in the file system cache that >>> contain dirty metadata and user data. The operation then suspends any >>> new activity on the file system until the file system is thawed. >>> Any help would be appreciated, thanks a lot! Andy Zhang >> >> What you want is snapshotting. You can create a snapshot of UFS or ZFS >> filesystems, mount the snapshot and then back it up without needing to >> worry about the filesystem changing while you're trying to back it up. >> >> See mksnap_ffs(8) and the 'snapshot' entry in zfs(8) >> >> The snapshot is mounted separately from the actual filesystem which can >> carry on with normal activities in the mean time. >> >> Snapshotting functionality is built into dump(8) for UFS filesystems >> (See the -L flag in that man page) or you can use zfs send / recv to >> dump filesystems to tape, which implies use of snapshots. > > Snapshot is different functionality from what the OP asked. > Exactly requested feature is provided by UFSSUSPEND/UFSRESUME ioctls > on the /dev/ufssuspend, for UFS volumes. You should consult the code > to see how to use them. Do the VMWare tools currently implement this? VMWare doesnt complain when making snapshots, but I never found a way to verify its actually working. How about Xen and popular Xen variations like Amazon and Digital Ocean? Thanks, Charles > > I suspect that the similar feature exists for ZFS, but I do not know > where to start looking. > _______________________________________________ > freebsd-fs@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-fs > To unsubscribe, send any mail to "freebsd-fs-unsubscribe@freebsd.org"
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