Hello,

On Mon, 14 Dec 2015 11:46:43 +0800 xiafei wrote:

> Hi all,
>       I have a question about the I/O of cephfs.
> I configure cephfs with 2 OSDs, and 300PGs in two HDDs. Then I use the
> iostat (iostat -kx 1 /dev/sdd1) to monitor the I/Os of the HDDs
> (/dev/sdd1). The result is as follows:
> 
> 
> The iostat shows that there are write requests every second. However I
> do not execute any applications. What the source of the write I/O? 
> 
That's why you use atop and/or iotop to determine what program is writing
to the disks.

If it is indeed Ceph (ceph-osd process) writing to the disk then the
question is indeed what causes that. 
I have no experience with CephFS, but quiescent RBD volume (mounted VM
images) does not produce I/O by itself.

You say that you're not running any application, but is the CephFS mounted
somewhere?

Regards,

Christian
-- 
Christian Balzer        Network/Systems Engineer                
ch...@gol.com           Global OnLine Japan/Rakuten Communications
http://www.gol.com/
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