Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
On Wed, May 16, 2012 at 09:11:05PM +0100, Matthew Bloch wrote: > I'm trying to understand a symptom for a client who uses drbd to run > sets of virtual machines between three pairs of servers (v1a/v1b, > v2a/v2b, v3a/v3b), and I wanted to understand a bit better how DRBD I/O > is buffered depending on what mode is chosen, and buffer settings. > > Firstly, it surprised me that even in replication mode "A", the system > still seemed limited by by the bandwidth between nodes. I found this > out when the customer's bonded interface had flipped over to its 100Mb > backup connection, and suddenly they had I/O problems. While I was > investigating this and running tests, I noticed that switching to mode A > didn't help, even when measuring short transfers that I'd expect would > fit into reasonable-sized buffers. What kind of buffer size can I > expect from an "auto-tuned" DRBD? It seems important to be able to > cover bursts without leaning on the network, so I'd like to know whether > that's possible with some special tuning. Uhm, well, we have invented the DRBD Proxy specifically for that purpose. > The other problem is the "PingAck not received" messages that have been > littering the logs of the v3a/v3b servers for the last couple of weeks, > e.g. this has been happening every few hours for one DRBD or another: > > May 14 08:21:45 v3b kernel: [661127.869500] block drbd10: PingAck did > not arrive in time. Increase ping timeout? -- : Lars Ellenberg : LINBIT | Your Way to High Availability : DRBD/HA support and consulting http://www.linbit.com