Re: Does XFS prevent disk spindown?

Timothy Shimmin
2008-04-07T01:05:14Z

Thor Kristoffersen wrote:
> (It looks like my reply never made it to the list so I'm trying again.)
>
> Eric Sandeen <sandeen@sandeen.net> writes:
>> David Chinner wrote:
>>> On Mon, Mar 31, 2008 at 08:26:00PM +0200, Thor Kristoffersen wrote:
>>>> I've noticed that when I spin down XFS-mounted disks they spin up again
>>>> shortly afterwards. I used iostat to monitor disk accesses to a mounted
>>>> partition (with noatime) in single user mode. Apparently there is a write
>>>> access to the partition approximately every 35 seconds, even if the
>>>> partition is idle. As far as I can understand, since there is no data that
>>>> needs to be flushed this must be done by an XFS daemon for some purpose.
>> Use blktrace, or echo 1 > /proc/sys/vm/block_dump to see what block and
>> who's writing it... it's probably the superblock? what kernel?
>
> This is kernel version 2.6.24. More specifically it's a Debian kernel from
> package linux-image-2.6.24-1-686 (2.6.24-4).
>
> I put the system in runlevel 1 and executed the test as you suggested. On
> /dev/sda3 I have mounted (with noatime) an XFS filesystem that contains
> data that is not supposed to be accessed by any process. In the output
> below I have filtered out all accesses to other partitions. (BTW, this is
> not actually the disk that I wanted to spin down, but I think the log
> proves my point.)
>
>
I'm wondering if that is writing to the xfs ondisk log/journal in those cases.
What does 'xfs_logprint -t' show in these "idle" states
after these writes?

--Tim

> Thor
>
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