Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
On Thu, 29 Mar 2007, Duane Cox wrote: > > Try running it longer, like 10x as long. Also, just to test it, try > > making a single-disk software raid1 out of /dev/sdb and telling drbd to > > use /dev/mdwhatever as it's backing store. I've seen wacky performance > > differences depending on the "most close" block device underlying a > > given store. Easily demonstrated with raw device access with aoe (aoe > > will use 512b frames if you just dd to the device, whereas if you use md > > on top of the aoe device you'll get multiples of 512b frames). > > Please help me see the light... > > How does the advice above have anything to do with writing to /dev/sdb > (which is just a single 36G 15K U160 seagate) when clearly write > performace to /dev/sdb degrades with each additional passing of the > bechmark command and only when the drbd module is loaded and not even > in a connnected state? > > (drbd loaded in disconnected state) > initially I get ~70 MB/s write througput to /dev/sdb > eventually I get ~30 MB/s write througput to /dev/sdb > possible even gets worse, I just stopped testing at this point. ^^^ I was suspecting caching. Using an additional block layer, can alter how and when things are cached. > Then I STOP/UNLOAD drbd > now I get ~70 MB/s write throughpout to /dev/sdb again. ^^^ I didn't know that when I responded. -- Jon Nelson <jnelson-drbd at jamponi.net>