# [OmniOS-discuss] arcstat ZFS question

Richard Skelton skeltonr at btconnect.com
Fri Mar 17 23:50:00 UTC 2017

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    Hi Dan,
    Thanks for the prompt response.

    But why the arc misses if I repeat the du and why is the L2arc size from
    arcstat much bigger than from zpool iostat?

    Dan McDonald wrote:
    >> On Mar 17, 2017, at 4:12 AM, Richard Skelton <skeltonr at btconnect.com> wrote:
    >>
    >> Why does du generate writes?
    >> Is this normal?
    >>
    >
    > If you've L2ARC, it'd make sense that du (a program that traverses tons of directories if not more to find out how many blocks and/or bytes each file holds) would change the usage patterns AND that it would get cached in your L2ARC device.  Caches are written when usage patterns change.
    >
    > So yes, it's expected behavior:  caches change based on usage patterns, and "du -sh *" changes your usage to "read every directory".
    >
    > Hope this helps,
    > Dan
    >
    >
    >
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