Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
Hi Folks! Has anyone measured the drbd overhead??? I have two serious Sun servers syncing a 50gig partition via drbd with protocol C, in active/active configuration. The servers have a dedicated 1000mbit interface for drbd connected via a cross-cable. The synced volume has an ocfs2 filesystem using the dedicated link, too. The sync-speed is limited to 100M, so there is a little bit left for the ocfs2-locking. One of the two nodes is my "application-active", meaning apache running and mysql running on the drbd volume, the other node is my "application-passive", which will be activated, if the first is down. Yesterday I had to benchmark the volume, because I had some performance issues. I made 3 tests with Unixbench - fs A. on drbd-volume as it is. Replication in protocol C activated B. on drbd-volume, replication stopped (other node shut down) C. on physical ext3 partition, to test the subsystems performance My (selected) results are: Results =========== File Read 1024 bufsize, 2000 blocks ----------------------------------- 1 thread 4 threads A: 72,10 MB/s 69,73 MB/s B: 73,84 MB/s 77,62 MB/s C: 102,15 MB/s 231,92 MB/s File Write 1024 bufsize, 2000 blocks ------------------------------------ 1 thread 4 threads A: 16,48 MB/s 11,62 MB/s B: 17,65 MB/s 12,70 MB/s C: 46,19 MB/s 28,08 MB/s File Read 4096 bufsize, 8000 blocks ----------------------------------- 1 thread 4 threads A: 177,32 MB/s 307,13 MB/s B: 178,84 MB/s 301,32 MB/s C: 198,46 MB/s 469,85 MB/s File Write 4096 bufsize, 8000 blocks ------------------------------------ 1 thread 4 threads A: 57,69 MB/s 43,69 MB/s B: 63,44 MB/s 45,38 MB/s C: 161,90 MB/s 90,30 MB/s As you can see, the syncing with protocol C has no noticeable overhead, maybe 7 or 8% compared to drbd-standalone. But I think that the drbd subsystem has a serious read overhead of 40% and write overhead of around 150% compared to non-drbd'd volumes. Does anybody notice performance results like mine? I use: Drbd 8.0.14 shipped with Debian Lenny Ocfs2 1.4.1 shipped with Debian Lenny Two Dual-Opteron 2216 Sun servers with 73G SAS 15K disks in RAID 1 configuration Kind regards Marco Fischer -------------- next part -------------- A non-text attachment was scrubbed... Name: Marco Fischer (mf at brainbits.net).vcf Type: text/x-vcard Size: 436 bytes Desc: Marco Fischer (mf at brainbits.net).vcf URL: <http://lists.linbit.com/pipermail/drbd-user/attachments/20090716/5d781523/attachment.vcf>