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Re: [zfs-discuss] Introducing zilstat

Subject: Re: [zfs-discuss] Introducing zilstat
From: Richard Elling
Date: Wed, 04 Feb 2009 21:20:13 -0800
Marion Hakanson wrote:
> The zilstat tool is very helpful, thanks!
>
> I tried it on an X4500 NFS server, while extracting a 14MB tar archive,
> both via an NFS client, and locally on the X4500 itself.  Over NFS,
> said extract took ~2 minutes, and showed peaks of 4MB/sec buffer-bytes
> going through the ZIL.
>
> When run locally on the X4500, the extract took about 1 second, with
> zilstat showing all zeroes.  I wonder if this is a case where that
> ZIL bypass kicks in for >32K writes, in the local tar extraction.
> Does zilstat's underlying dtrace include these bypass-writes in the
> totals it displays?
>   

This is what I would expect. What you are seeing is the affect of the
NFS protocol and how the server commits data to disk on behalf of
the client -- by using sync writes.


> I think if it's possible to get stats on this bypassed data, I'd like
> to see it as another column (or set of columns) in the zilstat output.
>   

Yes.  I've got a few more columns in mind, too.  Does anyone still use
a VT100? :-)
 -- richard

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