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From: | Robert Nichols |
Subject: | Re: [rdiff-backup-users] Incredibly slow i/o to NAS server |
Date: | Mon, 5 Dec 2016 15:26:38 -0600 |
User-agent: | Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.5.0 |
On 12/05/2016 09:28 AM, Joe Steele wrote:
On 12/4/2016 9:58 AM, Robert Nichols wrote:On 12/03/2016 09:32 PM, Andrea Bolandrina wrote:What problems does rdiff-backup have with hard linked content? As far as I know hard links should be supported...Supported? Yes, but with plenty of bugs. If links are added and removed from a set, you can end up with two or more separate subsets (i.e., what should be a set of 10 links to a single file becomes 3 files with link counts of 3, 5, and 2), and the link arrangement in the metadata files won't always match the link arrangement in the mirror. The checksum is stored only for the first link in the collating sequence. If that first link gets deleted, the checksum is lost. If a link with a path that comes earlier in the collating sequence is added, it sometimes does not inherit the checksum. I have a massive and time-consuming audit that I run after every backup session to patch that up. Verification always complains about missing checksums for all the links that do no have one stored. I have to filter out all the verbose 2-line messages for those from the verification report.I believe the harlink problems you describe are identified in this bug report (that I submitted in 2009): http://savannah.nongnu.org/bugs/?func=detailitem&item_id=26848 Attached to the report are patches to fix the issue. Some distros (which I think include Debian, Ubuntu, & Suse) have since been including the patches as part of their packaging.
Those patches look like they address the problems with checksums being misplaced or lost, but they don't appear to have anything to do with what I see as the greater problem of sets of hard links being broken up and inconsistencies between the hard link counts in the metadata and the mirror. I finally got rdiff-backup to build (needed a patch for librsync >= 1.0.0), so I can do some testing later. -- Bob Nichols "NOSPAM" is really part of my email address. Do NOT delete it.
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