[CentOS] DRBD very slow....
Ross Walker
rswwalker at gmail.com
Mon Jul 27 22:18:07 UTC 2009
On Jul 27, 2009, at 4:09 PM, Coert Waagmeester <lgroups at waagmeester.co.za
> wrote:
>
> On Mon, 2009-07-27 at 12:37 +0200, Coert Waagmeester wrote:
>> On Mon, 2009-07-27 at 12:02 +0200, Alexander Dalloz wrote:
>>>>
>>>> On Mon, 2009-07-27 at 08:30 +0200, Coert Waagmeester wrote:
>>>
>>>>> Hello Roman,
>>>>>
>>>>> I am running drbd 8.2.6 (the standard centos version)
>>>
>>>
>>> have you considered to test the drbd-8.3 packages?
>>>
>>> http://bugs.centos.org/view.php?id=3598
>>>
>>> http://dev.centos.org/centos/5/testing/{i386,x86_64}/RPMS/
>>>
>>
>> Thank you very much for this tip! It was one very obvious place
>> where I
>> did not look yet.
>>
>>
>> Would it be necessary to still recompile it for the TCP_NODELAY and
>> such?
>>
>> I am just making sure, because
>> http://www.nabble.com/Huge-latency-issue-with-8.2.6-td18947965.html
>> makes it seem unnecessary.
>>
>> Why do the repositories provide both DRBD 8.0.x and 8.2.6?
>>
>
> Here is a status update....
> _______________________________________________________________________________
> on both hosts I now run from the testing repository:
> # rpm -qa | grep drbd
> drbd83-8.3.1-5.el5.centos
> kmod-drbd83-xen-8.3.1-4.el5.centos
> _______________________________________________________________________________
> Here is my config (slightly condensed):
> -----------------------------------------------------
> global {
> usage-count yes;
> }
> common {
> protocol C;
> syncer { rate 50M; }
> net {
> # allow-two-primaries; }
> sndbuf-size 0; }
> # disk {no-disk-flushes;
> # no-md-flushes; }
> startup { wfc-timeout 0 ; }
> }
> resource xenfilesrv {
> device /dev/drbd1;
> disk /dev/vg0/xenfilesrv;
> meta-disk internal;
>
> on baldur.mydomain.local {
> address 10.99.99.1:7788;
> }
> on thor.mydomain.local {
> address 10.99.99.2:7788;
> }
> }
> resource xenfilesrvdata {
> device /dev/drbd2;
> disk /dev/vg0/xenfilesrvdata;
> meta-disk internal;
>
> on baldur.mydomain.local {
> address 10.99.99.1:7789;
> }
> on thor.mydomain.local {
> address 10.99.99.2:7789;
> }
> }
> _______________________________________________________________________________
>
> xenfilesrv is a xen domU
> in this domU i ran a dd with oflag direct:
> ---------------------------------------------------------
> # dd if=/dev/zero of=1gig.file bs=1M count=1000 oflag=direct
> 1000+0 records in
> 1000+0 records out
> 1048576000 bytes (1.0 GB) copied, 147.997 seconds, 7.1 MB/s
>
> Just before I ran the dd this popped up in the secondary hosts syslog:
> ----------------------------------------------------------------------
> Jul 27 21:51:42 thor kernel: drbd2: Method to ensure write ordering:
> flush
> Jul 27 21:51:42 thor kernel: drbd1: Method to ensure write ordering:
> flush
>
>
> _______________________________________________________________________________
>
> What more can I try?
>
> To be quite honest, I have no idea what to do with/ where to find the
> TCP_NODELAY socket options......
Use drbd option to disable flush/sync, but understand that during a
power failure or system crash data will not be consistent on disk and
you will need to sync the storage from the other server.
-Ross
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