From mboxrd@z Thu Jan 1 00:00:00 1970 From: Robert Collins Subject: BackupPC, per-dir hard link limit, Debian packaging Date: Tue, 02 Mar 2010 13:29:05 +1100 Message-ID: <1267496945.9222.155.camel@lifeless-64> Mime-Version: 1.0 Content-Type: multipart/signed; micalg="pgp-sha1"; protocol="application/pgp-signature"; boundary="=-IP9TtOA9ArFD5Wi/227b" To: linux-btrfs@vger.kernel.org Return-path: List-ID: --=-IP9TtOA9ArFD5Wi/227b Content-Type: text/plain; charset="ANSI_X3.4-1968" Content-Transfer-Encoding: quoted-printable I realise that the hard link limit is in the queue to fix, and I read the recent thread as well as the older (october I think) thread. I just wanted to note that BackupPC *does* in fact run into the hard link limit, and its due to the dpkg configuration scripts. BackupPC hard links files with the same content together by scanning new files and linking them together, whether or not they started as a hard link in the backed up source PCs. It also builds a directory structure precisely matching the source machine (basically it rsyncs across, then hardlinks aggressively). If you back up a Debian host, /var/lib/dpkg/info contains many identical files because debhelper generates the same script in the common case: ls /var/lib/dpkg/info/*.postinst | xargs -n1 sha1sum | awk '{ print $1 }' | sort -u | wc -l 862 ls /var/lib/dpkg/info/*.postinst | wc -l 1533 As I say, I realise this is queued to get addressed anyway, but it seems like a realistic thing for people to do (use BackupPC on btrfs) - even if something better still can be written to replace the BackupPC store in the future. I will note though, that simple snapshots won't achieve the deduplication level that BackupPC does, because the fils don't start out as the same: they are identified as being identical post-backup. Cheers, Rob --=-IP9TtOA9ArFD5Wi/227b Content-Type: application/pgp-signature; name="signature.asc" Content-Description: This is a digitally signed message part -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.10 (GNU/Linux) iEYEABECAAYFAkuMd/AACgkQhnv5qfvT646bgACgoBEHvkUU5kjcwGDpdZME2ToE MKQAn07gznbGhSC3jgxr/EfHMN0/kGAh =G8Zj -----END PGP SIGNATURE----- --=-IP9TtOA9ArFD5Wi/227b--