Major - P3 Title is clear, allocating 2GB files takes no time / no space on disk, and thus disk fragmentation can occur.
# mkdir /tmp/x # mongod --dbpath /tmp/x --port 27111 --replSet rs1 --oplogSize 10000 # mongo --port 27111 > rs.initiate()
Sat Nov 30 08:02:11.712 [FileAllocator] allocating new datafile x/local.1, filling with zeroes... Sat Nov 30 08:02:11.796 [FileAllocator] done allocating datafile x/local.1, size: 2047MB, took 0.084 secs Sat Nov 30 08:02:11.797 [FileAllocator] allocating new datafile x/local.2, filling with zeroes... Sat Nov 30 08:02:11.801 [FileAllocator] done allocating datafile x/local.2, size: 2047MB, took 0.004 secs Sat Nov 30 08:02:11.801 [FileAllocator] allocating new datafile x/local.3, filling with zeroes... Sat Nov 30 08:02:11.805 [FileAllocator] done allocating datafile x/local.3, size: 2047MB, took 0.003 secs Sat Nov 30 08:02:11.805 [FileAllocator] allocating new datafile x/local.4, filling with zeroes... Sat Nov 30 08:02:11.810 [FileAllocator] done allocating datafile x/local.4, size: 2047MB, took 0.005 secs Sat Nov 30 08:02:11.811 [FileAllocator] allocating new datafile x/local.5, filling with zeroes... Sat Nov 30 08:02:11.815 [FileAllocator] done allocating datafile x/local.5, size: 2047MB, took 0.004 secs
# ll -h total 1032 drwxr-xr-x 2 root wheel 512B Nov 30 08:02 _tmp/ drwxr-xr-x 2 root wheel 512B Nov 30 08:04 journal/ -rw------- 1 root wheel 64M Nov 30 08:02 local.0 -rw------- 1 root wheel 2G Nov 30 08:02 local.1 -rw------- 1 root wheel 2G Nov 30 08:02 local.2 -rw------- 1 root wheel 2G Nov 30 08:02 local.3 -rw------- 1 root wheel 2G Nov 30 08:02 local.4 -rw------- 1 root wheel 2G Nov 30 08:02 local.5 -rw------- 1 root wheel 16M Nov 30 08:02 local.ns -rwxr-xr-x 1 root wheel 0B Nov 30 08:04 mongod.lock* # du -sh 1.0M .