Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
On Dec 18, 2007 10:41 AM, Lars Ellenberg <lars.ellenberg at linbit.com> wrote: > On Tue, Dec 18, 2007 at 07:13:05PM +0100, Lars Ellenberg wrote: > > please do > > one-node# ping -w 10 -f -s 4100 replication-link-ip-of-other-node > > and show me the output. > > also, > > 1) > drbdadm disconnect you-resource-name > drbd now StandAlone Primary/Unknown > dd if=/dev/zero bs=4096 count=10000 of=/some/file/on/your/drbd oflag=dsync > > 2) > drbdadm adjust all > wait for the resync > drbd now Connected Primary/Secondary > dd if=/dev/zero bs=4096 count=10000 of=/some/file/on/your/drbd oflag=dsync > > 3) > dd if=/dev/zero bs=4096 count=10000 of=/some/file/NOT/on/your/drbd oflag=dsync > > do each dd command several times, > do this when nothing else happens on the box. > > the important part here is the "dsync" flag. > if your dd does not know about that, upgrade. > > the dd bs=4096 count=10000 oflag=sync > (many small requests, each single one of them synchronous by itself) > is to give an idea for the average latency of one single write request, > * with drbd disconnected > * with drbd connected > * without drbd (should be as close as possible to the lower level > device of drbd, preferably on the same hardware) OK, here are the results: Test 1: DRBD Disconnected [node1 ~]$ 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, 3.14315 seconds, 13.0 MB/s [node1 ~]$ 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, 3.05737 seconds, 13.4 MB/s [node1 ~]$ 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, 3.08115 seconds, 13.3 MB/s [node1 ~]$ 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, 3.17052 seconds, 12.9 MB/s [node1 ~]$ 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, 3.0727 seconds, 13.3 MB/s Test 2: DRBD Connected [node1 ~]$ 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, 11.8043 seconds, 3.5 MB/s [node1 ~]$ 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, 11.9506 seconds, 3.4 MB/s [node1 ~]$ 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, 12.2863 seconds, 3.3 MB/s [node1 ~]$ 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, 11.203 seconds, 3.7 MB/s [node1 ~]$ 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, 11.212 seconds, 3.7 MB/s Test 3: Non-DRBD [node1 ~]$ 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, 3.14307 seconds, 13.0 MB/s [node1 ~]$ 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, 2.98458 seconds, 13.7 MB/s [node1 ~]$ 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, 2.95751 seconds, 13.8 MB/s [node1 ~]$ 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, 2.90936 seconds, 14.1 MB/s [node1 ~]$ 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, 3.04481 seconds, 13.5 MB/s