[DRBD-user] drbd overhead

dhz_bf at walla.co.il dhz_bf at walla.co.il
Tue May 4 15:41:44 CEST 2004

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


I have performed an experiment to get some idea about the overhead of drbd when its partner (the secondary node) is down.
I am using version 0.6.12 of drbd.

The drbd has been in CState of  WFConnection.

I have performed a certain operation on the disk and it tool about 5.5 minutes when drbd was loaded and "owned" the disk on which the operation was performed.  The operation involved tar and gzip.

I then took drbd down and mounted the partitions drbd "owns" directly.  I retried the operation and it took 4.5 minutes.

There was an additional factor that the disk drbd "owns" contains the file system of a number of remote machines.  These machines were idle at the time of the experiment.

I looked at the code and it seemed to me like the overhead of drbd when the secondary node is down (and CState < Connected) is pretty small.  Yet, the times I measured with this experiment show about 25% overhead of drbd.

Do these results look like the ones you got in your experiments?  Is this level of overhead reasonable?

Thanks,

Doron Zifrony
BladeFusion Technologies
dhz_bf at walla.co.il

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