scan_extents using 8 threads took 82 hours for my cluster holding 120M files on 12 OSDs with 1gbps between nodes. I would have gone with lot more threads if I had known it only operated on data pool and the only problem was network latency. If I recall correctly, each worker used up to 800mb ram so beware the OOM killer.
scan_inodes runs several times faster but I don’t remember exact timing.
In your case I believe scan_extents & scan_inodes can be done in a few hours by running the tool on each OSD node, but scan_links will be painfully slow due to it’s single-threaded nature.
In my case I ended up getting MDS to start and copied all data to a fresh filesystem ignoring errors.
scan_inodes runs several times faster but I don’t remember exact timing.
In your case I believe scan_extents & scan_inodes can be done in a few hours by running the tool on each OSD node, but scan_links will be painfully slow due to it’s single-threaded nature.
In my case I ended up getting MDS to start and copied all data to a fresh filesystem ignoring errors.
On Nov 4, 2018, 02:22 +0300, Rhian Resnick <xantho@xxxxxxxxxxxx>, wrote:
For a 150TB file system with 40 Million files how many cephfs-data-scan threads should be used? Or what is the expected run time. (we have 160 osd with 4TB disks.)_______________________________________________
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