[DRBD-user] Poor DRBD performance, HELP!

Cristian Mammoli - Apra Sistemi c.mammoli at apra.it
Mon Jun 20 12:06:07 CEST 2011


On 06/20/2011 07:16 AM, Noah Mehl wrote:
>
>
> On Jun 20, 2011, at 12:39 AM, Noah Mehl wrote:
>
>> On Jun 18, 2011, at 2:27 PM, Florian Haas wrote:
>>
>>> On 06/17/2011 05:04 PM, Noah Mehl wrote:
>>>> Below is the script I ran to do the performance testing.  I basically took the script from the user guide and removed the oflag=direct,
>>>
>>> ... which means that dd wrote to your page cache (read: RAM). At this
>>> point, you started kidding yourself about your performance.
>>
>> I do have a question here:  the total size of the dd write was 64GB, twice the amount of system RAM, does this still apply?
>>
>>>
>>>> because when it was in there, it brought the performance down to 26MB/s (not really my focus here, but maybe related?).
>>>
>>> "Related" doesn't begin to describe it.
>>>
>>> Rerun the tests with oflag=direct and then repost them.
>>
>> Florian,
>>
>> I apologize for posting again without seeing your reply.  I took the script directly from the user guide:
>>
>> #!/bin/bash
>> TEST_RESOURCE=r0
>> TEST_DEVICE=$(drbdadm sh-dev $TEST_RESOURCE)
>> TEST_LL_DEVICE=$(drbdadm sh-ll-dev $TEST_RESOURCE)
>> drbdadm primary $TEST_RESOURCE
>> for i in $(seq 5); do
>>   dd if=/dev/zero of=$TEST_DEVICE bs=512M count=1 oflag=direct
>> done
>> drbdadm down $TEST_RESOURCE
>> for i in $(seq 5); do
>>   dd if=/dev/zero of=$TEST_LL_DEVICE bs=512M count=1 oflag=direct
>> done
>>
>> Here are the results:
>>
>> 1+0 records in
>> 1+0 records out
>> 536870912 bytes (537 MB) copied, 0.911252 s, 589 MB/s
[...]

If your controller has a BBU change the write policy to writeback and 
disable flushes in your drbd.conf

HTH

-- 
Cristian Mammoli
APRA SISTEMI srl
Via Brodolini,6 Jesi (AN)
tel dir. +390731719822

Web   www.apra.it
e-mail  c.mammoli at apra.it


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