<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
</head>
<body style="overflow-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;">
<div dir="auto" style="overflow-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;">
On Apr 6, 2025, at 05:18, Rasool Almasikoupaei via lustre-discuss <lustre-discuss@lists.lustre.org> wrote:<br>
<div>
<blockquote type="cite"><br class="Apple-interchange-newline">
<div>
<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>
</div>
</blockquote>
<br>
</div>
<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>
<div>
<div dir="auto" style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; overflow-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;">
<div dir="auto" style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; overflow-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;">
<div>Cheers, Andreas</div>
<div>\u2014</div>
<div>Andreas Dilger</div>
<div>Lustre Principal Architect</div>
<div>Whamcloud/DDN</div>
</div>
<br class="Apple-interchange-newline">
</div>
<br class="Apple-interchange-newline">
<br class="Apple-interchange-newline">
</div>
<br>
</div>
</body>
</html>