<div dir="ltr"><br><div class="gmail_extra"><br><div class="gmail_quote">On Thu, May 4, 2017 at 4:36 PM, Xavier Hernandez <span dir="ltr"><<a href="mailto:xhernandez@datalab.es" target="_blank">xhernandez@datalab.es</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Hi,<span class=""><br>
<br>
On 30/04/17 06:03, Raghavendra Gowdappa wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
All,<br>
<br>
Its a common perception that the resolution of a file having linkto file on the hashed-subvol requires two hops:<br>
<br>
1. client to hashed-subvol.<br>
2. client to the subvol where file actually resides.<br>
<br>
While it is true that a fresh lookup behaves this way, the other fact that get's ignored is that fresh lookups on files are almost always prevented by readdirplus. Since readdirplus picks the dentry from the subvolume where actual file (data-file) resides, the two hop cost is most likely never witnessed by the application.<br>
</blockquote>
<br></span>
This is true for workloads that list directory contents before accessing the files, but there are other use cases that directly access the file without navigating through the file system. In this case fresh lookups are needed.<br></blockquote><div><br></div><div style="">I agree, if the contents of parent directory are not listed at least once, penalty is still there.</div><div style=""><br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<br>
Xavi<div class="HOEnZb"><div class="h5"><br>
<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<br>
A word of caution is that I've not done any testing to prove this observation :).<br>
<br>
regards,<br>
Raghavendra<br>
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</blockquote>
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</div></div></blockquote></div><br><br clear="all"><div><br></div>-- <br><div class="gmail_signature" data-smartmail="gmail_signature">Raghavendra G<br></div>
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