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<div>hi Stephan, </div>
<div><br>
</div>
<div>there is, see mmchconfig man page : <br>
<br>
</div>
<div>nsdCksumTraditional</div>
<div>This attribute enables checksum data-integrity checking between a traditional NSD client node and its NSD server. Valid values are yes and no. The default value is no.</div>
<div>(Traditional in this context means that the NSD client and server are configured with IBM Spectrum Scale rather than with IBM Spectrum Scale RAID. </div>
<div>The latter is a component of IBM Elastic Storage Server (ESS) and of IBM GPFS Storage Server (GSS).)</div>
<div><br>
</div>
<div>The checksum procedure detects any corruption by the network of the data in the NSD RPCs that are exchanged between the NSD client and the </div>
<div>server. A checksum error triggers a request to retransmit the message.</div>
<div><br>
</div>
<div>When this attribute is enabled on a client node, the client indicates in each of its requests to the server that it is using checksums. The server uses checksums only in</div>
<div>response to client requests in which the indicator is set. A client node that accesses a file system that belongs to another cluster can use checksums in the same way.</div>
<div><br>
</div>
<div>You can change the value of the this attribute for an entire cluster without shutting down the mmfsd daemon, or for one or more nodes without restarting the nodes.</div>
<div><br>
</div>
<div>Note:</div>
<div>* Enabling this feature can result in significant I/O performance degradation and a considerable increase in CPU usage.</div>
<div><br>
</div>
<div>* To enable checksums for a subset of the nodes in a cluster, issue a command like the following one:</div>
<div> mmchconfig nsdCksumTraditional=yes -i -N <subset-of-nodes></div>
<div><br>
</div>
<div> The -N flag is valid for this attribute.</div>
<div><br>
</div>
<div><span>
<pre>-- <br></pre>
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<div>-----Original Message-----</div>
<div><b>From</b>: Stephan Graf <<a href="mailto:Stephan%20Graf%20%3cst.graf@fz-juelich.de%3e">st.graf@fz-juelich.de</a>></div>
<div><b>Reply-To</b>: gpfsug main discussion list <<a href="mailto:gpfsug%20main%20discussion%20list%20%3cgpfsug-discuss@gpfsug.org%3e">gpfsug-discuss@gpfsug.org</a>></div>
<div><b>To</b>: gpfsug-discuss <<a href="mailto:gpfsug-discuss%20%3cgpfsug-discuss@gpfsug.org%3e">gpfsug-discuss@gpfsug.org</a>></div>
<div><b>Subject</b>: [EXTERNAL] [gpfsug-discuss] Protection against silent data corruption</div>
<div><b>Date</b>: Thu, 02 Jun 2022 16:31:43 +0200</div>
<div><br>
</div>
<div>Hi,<br>
</div>
<div><br>
</div>
<div>I am wondering if there is an option in SS to enable some checking to <br>
</div>
<div>detect silent data corruption.<br>
</div>
<div><br>
</div>
<div>Form GNR I know that there is End-to-End integrity. So a checksum is <br>
</div>
<div>stored in addition.<br>
</div>
<div><br>
</div>
<div>The background is that we are facing an issue where in some files (which <br>
</div>
<div>have data replication = 2) the mmrestripefile is reporting, that one <br>
</div>
<div>block is mismatching it's copy (the storage cluster is running SS <br>
</div>
<div>without GNR).<br>
</div>
<div>We have validated that the copied block is fine, but the original one is <br>
</div>
<div>broken (and this is what is returned on read access).<br>
</div>
<div>SS right now in our installation is unable to determine which is the <br>
</div>
<div>correct one.<br>
</div>
<div>Is there any option to enable this kind of feature in SS? If not, does <br>
</div>
<div>it make sense to create an "IDEA" for it?<br>
</div>
<div><br>
</div>
<div>Stephan<br>
</div>
<div><br>
</div>
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