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<p>Thanks for the answer!</p>
<p>Best,<br>
Rasool<br>
</p>
<div class="moz-cite-prefix">On 07.04.25 20:07, Andreas Dilger
wrote:<br>
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On Apr 6, 2025, at 05:18, Rasool Almasikoupaei via
lustre-discuss <a class="moz-txt-link-rfc2396E" href="mailto:lustre-discuss@lists.lustre.org"><lustre-discuss@lists.lustre.org></a> wrote:<br>
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<div>Hi everyone,<br>
<br>
<br>
Just wondering if anyone knows what these metric values
actually mean and how I can make sense of them:<br>
<br>
obdfilter.testfs-OST0000.tot_granted<br>
obdfilter.testfs-OST0000.tot_pending<br>
obdfilter.testfs-OST0000.tot_dirty<br>
<br>
Appreciate any help!<br>
</div>
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<div>The "space grant" mechanism controls how much dirty data
can be cached on the clients (per OST) before the writes are
throttled. This avoids clients dirtying GB (or TB these days)
of data in RAM but the OST is actually out of space and cannot
write the data to persistent storage.</div>
<div><br>
</div>
<div>tot_granted = total amount of space granted to all clients
for this OST</div>
<div>tot_pending = total amount of dirty data in process of
being written (i.e. in RPCs)</div>
<div>tot_dirty = total amount of dirty data reported by clients</div>
<div><br>
</div>
<div>The clients send these values to the server with every
write RPC, so the server knows the client totals even before
the write RPCs are sent. This allows the server to
pre-emptively send more write grants to a client so that it
doesn't need to throttle writes, if there is still lots of
free space on the server.</div>
<br>
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<div>Cheers, Andreas</div>
<div>—</div>
<div>Andreas Dilger</div>
<div>Lustre Principal Architect</div>
<div>Whamcloud/DDN</div>
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