[DRBD-user] how to measure the time of one file's synchronization to secondary node

[Tomki]

thanks for answering !

I have another question.

Is the Write Speed on /dev/drbd0 equals to the Transmission Speed of
the data through the network?

thanks.


On Tue, Sep 21, 2010 at 11:40 PM, Lars Ellenberg
<lars.ellenberg at linbit.com> wrote:
> On Tue, Sep 21, 2010 at 09:30:06AM -0600, Mike Lovell wrote:
>> Tomki wrote:
>> >resource r0 {
>> > protocol C;
>> > startup { wfc-timeout 0; degr-wfc-timeout 120; }
>> > disk { on-io-error detach; }
>> >}
>> >
>> >If I copy a 1GB file to /mnt on primary node , how to measure the time
>> >of this file's synchronization to secondary node
>> >done completely.
>> according to the config you posted, you are using protocol C on the
>> drbd resource. the drbd.conf man pages says that with protocol C the
>> "write IO is reported as completed, if it has reached both local and
>> remote disk." in other words, when you write a file on the primary,
>> drbd will not return the write operation as completed until drbd has
>> written the blocks to the local disk as well as written it to the
>> disk on the remote node. this makes it really easy to measure the
>> time that it takes. just do `time cp /path/to/large/file
>> /mnt/new/path/to/large/file`. the write operations in the cp wont
>> complete until the data is on both disks.
>
> Uhm... page cache...
>
> rather do a "time cp $source $sink ; time sync",
> otherwise you only benchmark your memory bandwidth
> (assuming that the 1GiB file fits into your RAM).
>
> --
> : Lars Ellenberg
> : LINBIT | Your Way to High Availability
> : DRBD/HA support and consulting http://www.linbit.com
>
> DRBD® and LINBIT® are registered trademarks of LINBIT, Austria.
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