On Wed, Feb 01, 2012 at 08:46:54PM -0430, Jose Ildefonso Camargo Tolosa wrote: > Greetings, > > I'm doing some experimentation with DRBD and relatively low speed > links (~30Mbps), with latency around 34ms. I have this: > > 1. DRBD version: 8.3.7 (api:88/proto:86-91) > 2. Several virtual machine images on the DRBD volume. > 3. deadline scheduler by default. > 4. LVM on top of DRBD, and ext4 on top of this LVM. > > I did this: > > 1. I started 3 KVM VMs (mainly idle). > 2. I started to copy a big file (50GB) into DRBD partition. > 3. I started to use the VMs, mainly read-only operations, with some > small writes. > > At some point, the VMs just froze while trying to read. So, I went to > physical machine, and tried a "ls" on a directory inside the DRBD > volume, that I hasn't saw before (so it was not cached)... ls command > also froze.... access to cached data seems to be unaffected, then, I > stopped the cp process (ctrl-z), and waited for network traffic to > stop (patiently watching bwm). After network (replication) traffic > stopped: all unfroze. > > Now, my understanding is that DRBD reads are local, and thus: I can't > understand why writing would freeze the reads.... > > Any ideas?
Try the same without DRBD, I would expect similar effects. I suspect your are simply overloading your IO subsystem. -- : Lars Ellenberg : LINBIT | Your Way to High Availability : DRBD/HA support and consulting http://www.linbit.com _______________________________________________ drbd-user mailing list [email protected] http://lists.linbit.com/mailman/listinfo/drbd-user
