Re: [BackupPC-users] Problems with hardlink-based backups...
2009-09-01 13:04:35
Holger Parplies wrote:
> Hi,
>
> Jim Leonard wrote on 2009-08-31 23:55:10 -0500 [Re: [BackupPC-users] Problems
> with hardlink-based backups...]:
>> [...]
>> Why can't you use ext3 dump? (http://sourceforge.net/projects/dump/)
>
> I don't know the details of the dump program you are referring to, but those I
> have checked all have the limitation that the restore is run purely in user
> space, meaning that they will have the same problem with restoring the
> hardlinks. There is simply no syscall to create a hardlink by inode number
> (and for good reasons - you can't check visibility of an inode, only of a
> path, and please don't argue "root permission" ;-), so you still need to keep
> track of names for files with more than one hardlink. While it is totally
> possible for restore programs to be smart (i.e. specialized) enough to get
> around this limitation, it is equally possible that this was not recognized as
> a problem - hundreds of thousands of files with more than one link will "just
> work" on any reasonable hardware without special handling, and this is
> probably more by several orders of magnitude than an average file system will
> contain.
>
> So, my question is basically, have you tried restoring a dump, and have you
> got more than "works for me" to support that it will scale?
My experience with archives in the 100 to 700 gig range is that machines
that can complete backups easily every night and can do an image copy in
around 2 hours cannot complete a file oriented copy over a weekend using
any tools that I've found (dump/restore, tar, cpio, cp -a, etc.). While
it is true that all of those tools might 'just work' given enough time,
the point is that they have to work in the time you have to be
practical. And 'hundreds of thousands' isn't a big number - these would
be in the millions of files.
--
Les Mikesell
lesmikesell AT gmail DOT com
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