Alan, Unless noted otherwise all results posted are for block device readahead set to 16M using "blockdev --setra=16384 <block_device>". All are using the 2.6.9-11 Centos 4.1 kernel. For those who don't have lmdd, here is a comparison of two results on an ext2 filesystem: ============================================================================ [root@modena1 dbfast1]# time bash -c "(dd if=/dev/zero of=/dbfast1/bigfile bs=8k count=800000 && sync)" 800000+0 records in 800000+0 records out real 0m33.057s user 0m0.116s sys 0m13.577s [root@modena1 dbfast1]# time lmdd if=/dev/zero of=/dbfast1/bigfile bs=8k count=800000 sync=1 6553.6000 MB in 31.2957 secs, 209.4092 MB/sec real 0m33.032s user 0m0.087s sys 0m13.129s ============================================================================ So lmdd with sync=1 is apparently equivalent to a sync after a dd. I use 2x memory with dd for the *READ* performance testing, but let's make sure things are synced on both sides for this set of comparisons. First, let's test ext2 versus "ext3, data=ordered", versus reiserfs versus xfs:
