[DRBD-user] drbd performance with GbE in connected mode

Ralf Gross Ralf-Lists at ralfgross.de
Sun Jan 14 23:32:55 CET 2007

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


Ross S. W. Walker schrieb:
>> [drbd write performance over GbE]
> 
> First of all let me ask which benchmark tool you used for the
> sequential/random io runs? I like the information it provides and
> can use a tool like that.

It's tiobench (http://sourceforge.net/projects/tiobench/).
 
> Second, using Prot C, the writes do not return until they are
> committed to disk on both sides, so cannot the loss of throughput be
> attributed to the increased latency of writing on host1 while it
> sends out the write over 1Gbps wire to host2, who then writes it to
> disk and then sends a successful response back to host1 who then
> returns?
> 
> If the local write and send happened at the same time Copy/Send
> Latency + Gbps latency + Remote Write Latency + Gbps return latency
> = increased latency. How much increased latency depends on the
> speed/effectiveness of the network and the speed of the remote
> storage versus the speed of the local storage. The slowest storage
> is always the weakest link, try to get storage systems that are the
> same for most reliable performance.

Both Raid's are able to write with >120MB/s in disconnected mode.
I'm just wondering because I have seen people on the list that get
~95MB/s with a similar setup. 

Ralf



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