[DRBD-user] drbd Performance

nathan at robotics.net nathan at robotics.net
Wed Jul 16 19:05:53 CEST 2008

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


On Wed, 16 Jul 2008, Lars Marowsky-Bree wrote:

> On 2008-07-10T14:46:43, Stefan Novak <stefan.novak at bnet.at> wrote:
>
>> Hello!
>>
>> I test the I/O Performance using dm and bonnie. I am confused that the
>> drbd Performance is only the half than directly on the /dev/sda device.
>> For testing purposes I've only one single node because i want to test
>> the I/O of the SCSI Controller, not of DRBD.
>
> You're being hit by the internal metadata. Putting the metadata on
> another spindle will make it quite fast.

What is the metadata overhead in DRBD? I am seeing about 100 MB/s overhead 
with DRBD:

[root at xen1 /]# sync ; dd if=/dev/drbd0 of=/dev/null bs=4096 count=1M
1048576+0 records in
1048576+0 records out
4294967296 bytes (4.3 GB) copied, 14.6703 seconds, 293 MB/s

[root at xen1 /]# sync ; dd if=/dev/sdb of=/dev/null bs=4096 count=1M
1048576+0 records in
1048576+0 records out
4294967296 bytes (4.3 GB) copied, 10.4422 seconds, 411 MB/s


><>
Nathan Stratton                                CTO, BlinkMind, Inc.
nathan at robotics.net                         nathan at blinkmind.com
http://www.robotics.net                        http://www.blinkmind.com



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