Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
Maurice Volaski wrote: >> and then to benchmark: >> ./dm -x -a 0 -s 4g -b 20m -m -y -p -o /maurice/bonnie/hello > Here are the results for the two computers > primary (faster one) > 29.34 MB/sec (4294967296 B / 02:19.620474) > secondary (slower one) > 34.57 MB/sec (4294967296 B / 01:58.497313) > And why do they contradict the much faster results from dd? When using dd it's only writen to page-cache it doesnt it the disk if you got enough memory. My 2-cents on this: $ time dd if=/dev/zero of=hello bs=400M oflag=sync count=1 && time sync 1+0 records in 1+0 records out 419430400 bytes (419 MB) copied, 8.66923 seconds, 48.4 MB/s real 0m8.808s user 0m0.000s sys 0m1.548s real 0m0.337s <-- flush cache to disk using SYNC(1) user 0m0.000s sys 0m0.004s + ------------------------ Total 9.1 sec $ time dd if=/dev/zero of=hello bs=400M count=1 && time sync 1+0 records in 1+0 records out 419430400 bytes (419 MB) copied, 3.17573 seconds, 132 MB/s <- This is fictional imo real 0m3.307s user 0m0.000s sys 0m1.324s real 0m5.650s <-- sync user 0m0.000s sys 0m0.204s + ------------------------ Total 8.9 sec The write barrier of Protocol 'C' wants it really on disk -bypassing pagecache-, can someone confirm this?