Fwd: Re: Unexpected disk write activity with btrfs OSDs

Burkhard Linke <Burkhard.Linke@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> · Fri, 19 Jun 2015 09:06:33 +0200

    Forget the reply to the list...

      -------- Forwarded Message --------

            Subject:

            Re:  Unexpected disk write activity with
              btrfs OSDs

            Date: 
            Fri, 19 Jun 2015 09:06:33 +0200

            From: 
            Burkhard Linke
              <Burkhard.Linke@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx>

            To: 
            Lionel Bouton <lionel+ceph@xxxxxxxxxxx>

      Hi,

On 06/18/2015 11:28 PM, Lionel Bouton wrote:
> Hi,
*snipsnap*

> - Disks with btrfs OSD have a spike of activity every 30s (2 intervals
> of 10s with nearly 0 activity, one interval with a total amount of
> writes of ~120MB). The averages are : 4MB/s, 100 IO/s.

Just a guess:

btrfs has a commit interval which defaults to 30 seconds.

You can verify this by changing the interval with the commit=XYZ mount 
option.

Best regards,
Burkhard

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