[DRBD-user] Full resync vs real-time sync

Andrew (Anything) anything at starstrike.net
Thu Apr 30 23:12:20 CEST 2009

Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.

Im by no means an expert at this.

But im pretty sure that If your network is only able to do 120MB/sec that
would be the best youll get.

protocol C wont finish each write until it is sent over the network and
confirmed by the other side.


While syncing its probably faster because it just adds the writes to be done
on the end of the al-extents queue?


How are your nodes connected?




I'm getting an odd speed gap between the top speed of a full resync, and the
speed of actual writing to the primary connected node. On a full resync
(after invalidate), I'm getting about 400MB/s, however doing plain
sequential writes to the primary connected node (when fully synced of
course) only gives about 120MB/s. If I disconnect the node, the write speeds
are doubled. Both nodes are identical in this behavior, so there's no case
of one being slower than the other.

There's no notable difference in this behavior when changing the protocols
(even to A), al-extents or max-buffers. Is there anything else that I might
be missing?



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