[DRBD-user] Doc update and Sync performance

Josh Aune luken at fusionio.com
Wed Dec 30 19:45:22 CET 2009

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

On Dec 30, 2009, at 3:27 AM, Lars Ellenberg wrote:

> On Tue, Dec 29, 2009 at 03:56:17PM -0700, Josh Aune wrote:
>> Hi,
>> Attached is a patch for the users guide.
> Thanks.
>> Also, I'm having an issue with sync performance.  I have DRBD setup
>> between two hosts using SRP.
> SDP maybe?

Ya, that one :)

>> Under optimal conditions I'm able to achieve a 500+ MB/s write speed,
> How do you measure?

$ iostat -m 1

On both hosts while running a benchmark.  On the host with the benchmark I see 500+ MB/s register on both the drbd1 and fioa devices, on the remote host it registers 500 MB/s on only the fioa device.

While running the initial sync both sides register between 50-80 MB/s reads, no writes.  Doing a local benchmark using 4 processes of 32k reads this device can easily sustain 600+ MB/s.

>> but during the initial sync after the DRBD device is created the sync
>> proceeds at less than 100 MB/s.  Below is the config file.  Am I
>> missing anything needed to bump up the initial sync speed?
>> Also, all bytes on the drives on both side are zeros, so the limitation seems to be in the crc32c processing.
> Did you look at top, vmstat or similar?

Yes, 87% cpu idle.  Nothing much really happening.


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