On Aug 29, 2008 07:36 -0500, Eric Sandeen wrote: > at Ric & hch's request here is tar on the other fs's as well, re-sorted > by level 0 dump time. I put acp into the mix as well. > > Oh, and this time I remembered to set the elevator to something sane > (noop) for this storage, oops (was cfq last time) > > Also, this time the dup/tar/acp was written to /dev/null rather than > another filesystem. Interesting how routing to /dev/null alone changed > the ranking quite a bit. Note that tar has a (questionable) optimization when writing to /dev/null. It will NOT open the file or read the data, and just do the filename traversal to generate the file list and total file size. It does this by comparing the output file to "/dev/null": $ strace tar cvf /dev/null /t# mp/scheduler.pdf : [opening libs and stuff] : creat("/dev/null", 0666) = 3 fstat(3, {st_mode=S_IFCHR|0666, st_rdev=makedev(1, 3), ...}) = 0 write(1, "/tmp/scheduler.pdf\n", 19/tmp/scheduler.pdf ) = 19 lstat("/tmp/scheduler.pdf", {st_mode=S_IFREG|0664, st_size=150262, ...}) = 0 close(3) = 0 close(1) = 0 munmap(0x7f2c00dd7000, 4096) = 0 close(2) = 0 exit_group(0) = ? A way to get around this is to hard link to /dev/null and use that as output: # cp -a /dev/null /tmp/foo $ ls -l /tmp/foo 0 crw-rw-rw- 1 root root 1, 3 2008-08-18 18:15 /tmp/foo $ strace tar cvf /dev/null /t# mp/scheduler.pdf : [opening libs and stuff] : creat("/tmp/foo", 0666) = 3 fstat(3, {st_mode=S_IFCHR|0666, st_rdev=makedev(1, 3), ...}) = 0 stat("/dev/null", {st_mode=S_IFCHR|0666, st_rdev=makedev(1, 3), ...}) = 0 lstat("/tmp/scheduler.pdf", {st_mode=S_IFREG|0664, st_size=150262, ...}) = 0 open("/tmp/scheduler.pdf", O_RDONLY) = 4 write(1, "/tmp/scheduler.pdf\n", 19/tmp/scheduler.pdf) = 19 read(4, "%PDF-1.4\n%\303\244\303\274\303\266\303\237\n2 0 obj\n<</Le"..., 9728) = 9728 write(3, "tmp/scheduler.pdf\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 10240) = 10240 read(4, "\5\351\204\216\220N\224\304\344\331\355\366\264\216\311n\345\365\224\370\352.\205\354\341\0237\306\31>\201"..., 10240) = 10240 : [repeats] : write(3, "\253\2708\264\262\275\36\335\323\212\262\33\244\301\226\246\256d^\214n\246\220BW\363\306\25b%_L"..., 10240) = 10240 read(4, "i\264\364\243\264\220\327+u\3B\1\21\210\376\23\2035@D2\316t\356\271\v\37\210S\307]["..., 7414) = 7414 fstat(4, {st_mode=S_IFREG|0664, st_size=150262, ...}) = 0 close(4) = 0 write(3, "i\264\364\243\264\220\327+u\3B\1\21\210\376\23\2035@D2\316t\356\271\v\37\210S\307]["..., 10240) = 10240 close(3) = 0 close(1) = 0 munmap(0x7fb194cea000, 4096) = 0 close(2) = 0 exit_group(0) = ? Cheers, Andreas -- Andreas Dilger Sr. Staff Engineer, Lustre Group Sun Microsystems of Canada, Inc. -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html