Hi, I ran a set of benchmarks over different combinations of ext3 journaling on mirrored disks. I got some non-intuitive results. Could someone help me reason this ? Benchmarks ---------- I ran concurrently 4 processes, each process having a working set of 10MB. a) Process 0 creates 160 files each of size 64KB. b) Process 1 reads 160 files each of size 64KB. c) Process 2 creates 2560 dirs. Each dir is an empty dir but has a data block allocated to it. So, each dir is of size 4KB d) Process 3 stats 2560 files each of size 4KB. All the processes executes a sync() call before exiting and flushes all the data to disk. I created a RAID 0 (stripping) over two RAIDS each of which is a RAID 1 (totally there are 4 disks). I measured the performance of these benchmarks on three different setups (results are averaged over 20 runs). I) Mirroring with data journaling (data=journal) II) Mirroring with just metadata journaling (data=ordered) III) Mirroring with no journaling. Results ------- Each column gives the time taken in seconds. data=journal data=ordered NO journaling CREATE: 3.47096 5.46494 1.745721 READ: 3.11347 5.09944 1.80708 MKDIR: 3.38010 5.48238 1.7545 STAT: 2.96075 4.27023 1.98247 In the results, mirroring with no journaling performs better than the other two (as expected). However, the results look such that "mirroring with data journaling" performs better than "mirroring with metadata journaling". I don't know why this is happening. Any help is appreciated. Thanks. Vijayan _______________________________________________ Ext3-users@redhat.com https://www.redhat.com/mailman/listinfo/ext3-users
