Hello, My mate Michael and I have been steadily advancing our Gluster testing and today we finally reached some heavier conditions. The outcome was different from expectations built from our more basic testing so I think we have a couple of questions regarding the AFR/Replicate background threads that may need a developer's contribution. Any help appreciated. The setup is a 3 box environment, but lets start with two; SaturnM (Server) - 6core CPU, 16GB RAM, 1Gbps net - 3.2.6 Kernel (custom distro) - 3.2.5 Gluster (32bit) - 3x2TB drives, CFQ, EXT3 - Bricked up into a single local 6TB "distribute" brick - "brick" served to the network MMC (Client) - 4core CPU, 8GB RAM, 1Gbps net - Ubuntu - 3.2.5 Gluster (32bit) - Don't recall the disk space locally - "brick" from SaturnM mounted 500 x 15Gbyte files were copied from MMC to a single sub-directory on the brick served from SaturnM, all went well and dandy. So then we moved on to a 3 box environment; SaturnI (Server) = 1core CPU, 1GB RAM, 1Gbps net = 3.2.6 Kernel (custom distro) = 3.2.5 Gluster (32bit) = 4x2TB drives, CFQ, EXT3 = Bricked up into a single local 8TB "distribute" brick = "brick" served to the network SaturnM (Server/Client) - 6core CPU, 16GB RAM, 1Gbps net - 3.2.6 Kernel (custom distro) - 3.2.5 Gluster (32bit) - 3x2TB drives, CFQ, EXT3 - Bricked up into a single local 6TB "distribute" brick = Replicate brick added to sit over the local distribute brick and a client "brick" mapped from SaturnI - Replicate "brick" served to the network MMC (Client) - 4core CPU, 8GB RAM, 1Gbps net - Ubuntu - 3.2.5 Gluster (32bit) - Don't recall the disk space locally - "brick" from SaturnM mounted = "brick" from SaturnI mounted Now, in lesser testing in this scenario all was well - any files on SaturnI would appear on SaturnM (not a functional part of our test) and the content on SaturnM would appear on SaturnI (the real objective). Earlier testing used a handful of smaller files (10s to 100s of Mbytes) and a single 15Gbyte file. The 15Gbyte file would be "stat" via an "ls", which would kick off a background replication (ls appeared un- blocked) and the file would be transferred. Also, interrupting the transfer (pulling the LAN cable) would result in a partial 15Gbyte file being corrected in a subsequent background process on another stat. *However* .. when confronted with 500 x 15Gbyte files, in a single directory (but not the root directory) things don't quite work out as nicely. - First, the "ls" (at MMC against the SaturnM brick) is blocking and hangs the terminal (ctrl-c doesn't kill it). - Then, looking from MMC at the SaturnI file system (ls -s) once per second, and then comparing the output (diff ls1.txt ls2.txt | grep -v '>') we can see that between 10 and 17 files are being updated simultaneously by the background process - Further, a request at MMC for a single file that was originally in the 500 x 15Gbyte sub-dir on SaturnM (which should return unblocked with correct results) will; a) work as expected if there are less than 17 active background file tasks b) block/hang if there are more - Where-as a stat (ls) outside of the 500 x 15 sub-directory, such as the root of that brick, would always work as expected (return immediately, unblocked). Thus, to us, it appears as though there is a queue feeding a set of (around) 16 worker threads in AFR. If your request was to the loaded directory then you would be blocked until a worker was available, and if your request was to any other location, it would return unblocked regardless of the worker pool state. The only thread metric that we could find to tweak was performance/io-threads (which was set to 16 per physical disk; well per locks + posix brick stacks) but increasing this to 64 per stack didn't change the outcome (10 to 17 active background transfers). So, given the above, is our analysis sound, and if so, is there a way to increase the size of the pool of active worker threads? The objective being to allow unblocked access to an existing repository of files (on SaturnM) while a secondary/back-up is being filled, via GlusterFS? Note that I understand that performance (through-put) will be an issue in the described environment: this replication process is estimated to run for between 10 and 40 hours, which is acceptable so long as it isn't blocking (there's a production-capable file set in place). Any help appreciated. Thanks, -- Ian Latter Late night coder .. http://midnightcode.org/