On Fri, Jun 1, 2012 at 6:14 PM, Wiebe Cazemier <[email protected]> wrote: > Hi, > > I'm setting up a DRBD system and I don't really understand the performance > hits I'm getting. > > I have two hosts (with dedicated GB LAN): > > Host1: 3Ware 9650 SE SATA2 hardware RAID6, 5x 2TB disks > Host2: 2x250GB Linux MD RAID1. > > Example: a fully synced DRBD device with ext3 on it, writing a file with dd. > Writing on host1: > > dd if=/dev/zero of=groot1 bs=10M count=50 > 50+0 records in > 50+0 records out > 524288000 bytes (524 MB) copied, 8.04722 s, 65.2 MB/s
Sorry if I rant for a bit, but it's been _years_ since I wrote that part of the User's Guide, and it's been regurgitated a million times on this list, by myself and many others. Please, say it after me: I will not use dd without oflag=direct or oflag=dsync. I will not use dd without oflag=direct or oflag=dsync. I will not use dd without oflag=direct or oflag=dsync. You're kidding yourself. You're measuring *something*, a mix of caching effects and actual I/O, but not the throughput of your block device. Please rerun your tests with oflag=direct, and then come back with updated results. Florian -- Need help with High Availability? http://www.hastexo.com/now _______________________________________________ drbd-user mailing list [email protected] http://lists.linbit.com/mailman/listinfo/drbd-user
