Re: Why does stat() return invalid st_dev field for btrfs ??

[Chris Samuel <chris@csamuel.org>]

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On Tue, 18 Aug 2009 12:01:26 pm Mark Lord wrote:

> But really, it should be using DM/LVM when there are multiple devices.

Chris Mason addressed a number of these points in this January 2008 comment on 
LWN - http://lwn.net/Articles/265533/ - especially:

# This is something LVM cannot provide because it cannot maintain
# consistent checksums for the FS.

and

# When multiple devices are present, Btrfs will want to know it is
# mirroring on different physical spindles.  This is a challenge
# with LVM since the locations of physical extents can change without
# the FS knowing about it.  Even if there were hooks so the FS could
# know the current extent mappings, it would end up duplicating a copy
# of the mappings internally.

-- 
 Chris Samuel  :  http://www.csamuel.org/  :  Melbourne, VIC

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