Gluster users - Jul 2014 - performance/writebehind behavior

Hi folks,

Just wondering if anyone could clear up a question about expected 
behavior for the performance/writebehind translator.

I'm using Gluster 3.3, with a single volume which is distributed to two 
bricks on a pair of servers. I have performance.flush-behind=off; the 
documentation [1] leads me to expect (but doesn't say explicitly) that 
this will make close() block until the write has been flushed - but that 
isn't consistent with the behaviour I'm seeing:

$ dd if=/dev/zero of=/shared/vod/zero bs=1024 count=1000; wc -c 
/shared/vod/zero
1000+0 records in
1000+0 records out
1024000 bytes (1.0 MB) copied, 0.133975 s, 7.6 MB/s
1016832 /shared/vod/zero

As you can see, the wc doesn't see all of the data which has been 
written by dd.

If anyone could clear up whether or not this is expected, I'd be grateful.

Thanks

Richard

[1] 
http://gluster.org/community/documentation/index.php/Translators/performance/writebehind

CC write-behind Dev
On 07/10/2014 11:59 PM, Richard van der Hoff wrote:
> Hi folks,
>
> Just wondering if anyone could clear up a question about expected 
> behavior for the performance/writebehind translator.
>
> I'm using Gluster 3.3, with a single volume which is distributed to 
> two bricks on a pair of servers. I have performance.flush-behind=off; 
> the documentation [1] leads me to expect (but doesn't say explicitly) 
> that this will make close() block until the write has been flushed - 
> but that isn't consistent with the behaviour I'm seeing:
>
> $ dd if=/dev/zero of=/shared/vod/zero bs=1024 count=1000; wc -c 
> /shared/vod/zero
> 1000+0 records in
> 1000+0 records out
> 1024000 bytes (1.0 MB) copied, 0.133975 s, 7.6 MB/s
> 1016832 /shared/vod/zero
>
> As you can see, the wc doesn't see all of the data which has been 
> written by dd.
>
> If anyone could clear up whether or not this is expected, I'd be 
> grateful.
>
> Thanks
>
> Richard
>
> [1] 
>
http://gluster.org/community/documentation/index.php/Translators/performance/writebehind
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