<font size=2 face="Arial">Hi,</font><br><br><font size=2 face="Arial">>>How can it be that the I/O performance
degradation warning only seems to accompany the nsdCksumTraditional setting
and not GNR?</font><br><font size=2 face="Arial">>>Why is there such a penalty for "traditional"
environments?</font><br><br><font size=2 face="Arial">In GNR IO/NSD servers (ESS IO nodes), the
checksums are computed in parallel for a NSD (storage volume/vdisk)
across the threads handling each pdisk/drive (that constitutes the vdisk/volume).
This is possible since the GNR software on the ESS IO servers is tightly
integrated with underlying storage and is aware of the vdisk DRAID configuration
(strip-size, pdisk constituting vdisk etc.) to perform parallel checksum
operations. </font><br><br><font size=2 face="Arial">In non-GNR + external storage model, the
GPFS software on the NSD server(s) does not manage the underlying storage
volume (this is done by storage RAID controllers) and the checksum
is computed serially. This would contribute to increase in CPU usage and
I/O performance degradation (depending on I/O access patterns, I/O load
etc).</font><br><br><font size=2 face="Arial">My two cents.</font><br><br><font size=2 face="Arial">Regards,</font><br><font size=2 face="Arial">-Kums</font><br><br><br><br><br><br><font size=1 color=#5f5f5f face="sans-serif">From:
</font><font size=1 face="sans-serif">Aaron Knister <aaron.s.knister@nasa.gov></font><br><font size=1 color=#5f5f5f face="sans-serif">To:
</font><font size=1 face="sans-serif">gpfsug main discussion
list <gpfsug-discuss@spectrumscale.org></font><br><font size=1 color=#5f5f5f face="sans-serif">Date:
</font><font size=1 face="sans-serif">10/29/2018 12:34 PM</font><br><font size=1 color=#5f5f5f face="sans-serif">Subject:
</font><font size=1 face="sans-serif">[gpfsug-discuss]
NSD network checksums (nsdCksumTraditional)</font><br><font size=1 color=#5f5f5f face="sans-serif">Sent by:
</font><font size=1 face="sans-serif">gpfsug-discuss-bounces@spectrumscale.org</font><br><hr noshade><br><br><br><tt><font size=2>Flipping through the slides from the recent SSUG meeting
I noticed that <br>in 5.0.2 one of the features mentioned was the nsdCksumTraditional flag.
<br>Reading up on it it seems as though it comes with a warning about <br>significant I/O performance degradation and increase in CPU usage. I <br>also recall that data integrity checking is performed by default with <br>GNR. How can it be that the I/O performance degradation warning only <br>seems to accompany the nsdCksumTraditional setting and not GNR? As <br>someone who knows exactly 0 of the implementation details, I'm just <br>naively assuming that the checksum are being generated (in the same <br>way?) in both cases and transferred to the NSD server. Why is there such
<br>a penalty for "traditional" environments?<br><br>-Aaron<br><br>-- <br>Aaron Knister<br>NASA Center for Climate Simulation (Code 606.2)<br>Goddard Space Flight Center<br>(301) 286-2776<br>_______________________________________________<br>gpfsug-discuss mailing list<br>gpfsug-discuss at spectrumscale.org<br></font></tt><a href="http://gpfsug.org/mailman/listinfo/gpfsug-discuss"><tt><font size=2>http://gpfsug.org/mailman/listinfo/gpfsug-discuss</font></tt></a><tt><font size=2><br><br></font></tt><br><BR>