Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
Lars, Here are the results of the dd test on node2. Results look similar... > because we already had the case that identical hardware showed a factor > 100 different latency values. specifically, we just recently had two > DELL MD3000, one of which was showing 0.7 ms, the other one had > 70.x ms. and yes, the additional latency was attributed to drbd at > first, as well. only that on the same boxes, we had also other storage, > and there it behaved nicely. we have not been able to track it down to > the cause, but believe that resetting the storage made the effect > "go away". > > so do measure. Test 1: DRBD Disconnected [node2 ~]$ dd if=/dev/zero bs=4096 count=10000 of=/drbd/tmp/testfile oflag=dsync 10000+0 records in 10000+0 records out 40960000 bytes (41 MB) copied, 3.03173 seconds, 13.5 MB/s [node2 ~]$ dd if=/dev/zero bs=4096 count=10000 of=/drbd/tmp/testfile oflag=dsync 10000+0 records in 10000+0 records out 40960000 bytes (41 MB) copied, 3.00959 seconds, 13.6 MB/s [node2 ~]$ dd if=/dev/zero bs=4096 count=10000 of=/drbd/tmp/testfile oflag=dsync 10000+0 records in 10000+0 records out 40960000 bytes (41 MB) copied, 2.99447 seconds, 13.7 MB/s [node2 ~]$ dd if=/dev/zero bs=4096 count=10000 of=/drbd/tmp/testfile oflag=dsync 10000+0 records in 10000+0 records out 40960000 bytes (41 MB) copied, 2.9992 seconds, 13.7 MB/s [node2 ~]$ dd if=/dev/zero bs=4096 count=10000 of=/drbd/tmp/testfile oflag=dsync 10000+0 records in 10000+0 records out 40960000 bytes (41 MB) copied, 3.0024 seconds, 13.6 MB/s Test 2: DRBD Connected [node2 ~]$ dd if=/dev/zero bs=4096 count=10000 of=/drbd/tmp/testfile oflag=dsync 10000+0 records in 10000+0 records out 40960000 bytes (41 MB) copied, 18.553 seconds, 2.2 MB/s [node2 ~]$ dd if=/dev/zero bs=4096 count=10000 of=/drbd/tmp/testfile oflag=dsync 10000+0 records in 10000+0 records out 40960000 bytes (41 MB) copied, 17.0005 seconds, 2.4 MB/s [node2 ~]$ dd if=/dev/zero bs=4096 count=10000 of=/drbd/tmp/testfile oflag=dsync 10000+0 records in 10000+0 records out 40960000 bytes (41 MB) copied, 12.2118 seconds, 3.4 MB/s [node2 ~]$ dd if=/dev/zero bs=4096 count=10000 of=/drbd/tmp/testfile oflag=dsync 10000+0 records in 10000+0 records out 40960000 bytes (41 MB) copied, 12.1346 seconds, 3.4 MB/s [node2 ~]$ dd if=/dev/zero bs=4096 count=10000 of=/drbd/tmp/testfile oflag=dsync 10000+0 records in 10000+0 records out 40960000 bytes (41 MB) copied, 12.0736 seconds, 3.4 MB/s Test 3: Non-DRBD [node2 ~]$ dd if=/dev/zero bs=4096 count=10000 of=/tmp/testfile oflag=dsync 10000+0 records in 10000+0 records out 40960000 bytes (41 MB) copied, 3.14032 seconds, 13.0 MB/s [node2 ~]$ dd if=/dev/zero bs=4096 count=10000 of=/tmp/testfile oflag=dsync 10000+0 records in 10000+0 records out 40960000 bytes (41 MB) copied, 3.09048 seconds, 13.3 MB/s [node2 ~]$ dd if=/dev/zero bs=4096 count=10000 of=/tmp/testfile oflag=dsync 10000+0 records in 10000+0 records out 40960000 bytes (41 MB) copied, 3.0784 seconds, 13.3 MB/s [node2 ~]$ dd if=/dev/zero bs=4096 count=10000 of=/tmp/testfile oflag=dsync 10000+0 records in 10000+0 records out 40960000 bytes (41 MB) copied, 3.08517 seconds, 13.3 MB/s [node2 ~]$ dd if=/dev/zero bs=4096 count=10000 of=/tmp/testfile oflag=dsync 10000+0 records in 10000+0 records out 40960000 bytes (41 MB) copied, 3.06288 seconds, 13.4 MB/s