<font size=2 face="Arial">In non-GNR setup, nsdCksumTraditional=yes enables
data-integrity checking between a traditional NSD client node and its NSD
server, at the network level only.</font><br><br><font size=2 face="Arial">The ESS storage supports end-to-end checksum,
NSD client to the ESS IO servers (at the network level) as well as from
ESS IO servers to the disk/storage. This is further detailed
in the docs (link below):</font><br><br><a href="https://www.ibm.com/support/knowledgecenter/en/SSYSP8_5.3.1/com.ibm.spectrum.scale.raid.v5r01.adm.doc/bl1adv_introe2echecksum.htm"><font size=2 color=blue face="Arial">https://www.ibm.com/support/knowledgecenter/en/SSYSP8_5.3.1/com.ibm.spectrum.scale.raid.v5r01.adm.doc/bl1adv_introe2echecksum.htm</font></a><br><br><font size=2 face="Arial">Best,</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">Stephen Ulmer <ulmer@ulmer.org></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 04:52 PM</font><br><font size=1 color=#5f5f5f face="sans-serif">Subject:
</font><font size=1 face="sans-serif">Re: [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><font size=3>So the ESS checksums that are highly touted as "protecting
all the way to the disk surface" completely ignore the transfer between
the client and the NSD server? It sounds like you are saying that all of
the checksumming done for GNR is internal to GNR and only protects against
bit-flips on the disk (and in staging buffers, etc.)</font><br><br><font size=3>I’m asking because your explanation completely ignores
calculating anything on the NSD client and implies that the client could
not participate, given that it does not know about the structure of the
vdisks under the NSD — but that has to be a performance factor for both
types if the transfer is protected starting at the client — which it is
in the case of nsdCksumTraditional which is what we are comparing to ESS
checksumming.</font><br><br><font size=3>If ESS checksumming doesn’t protect on the wire I’d
say that marketing has run amok, because that has *definitely* been implied
in meetings for which I’ve been present. In fact, when asked if Spectrum
Scale provides checksumming for data in-flight, IBM sales has used it as
an ESS up-sell opportunity.</font><br><br><font size=3>-- </font><br><font size=3>Stephen<br><br></font><br><br><font size=3>On Oct 29, 2018, at 3:56 PM, Kumaran Rajaram <</font><a href="mailto:kums@us.ibm.com"><font size=3 color=blue><u>kums@us.ibm.com</u></font></a><font size=3>>
wrote:</font><br><br><font size=2 face="Arial">Hi,</font><font size=3><br></font><font size=2 face="Arial"><br>>>How can it be that the I/O performance degradation warning only
seems to accompany the nsdCksumTraditional setting and not GNR?<br>>>Why is there such a penalty for "traditional" environments?</font><font size=3><br></font><font size=2 face="Arial"><br>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><font size=3><br></font><font size=2 face="Arial"><br>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><font size=3><br></font><font size=2 face="Arial"><br>My two cents.</font><font size=3><br></font><font size=2 face="Arial"><br>Regards,<br>-Kums</font><font size=3><br><br><br><br><br></font><font size=1 color=#5f5f5f face="sans-serif"><br>From: </font><font size=1 face="sans-serif">Aaron
Knister <</font><a href="mailto:aaron.s.knister@nasa.gov"><font size=1 color=blue face="sans-serif"><u>aaron.s.knister@nasa.gov</u></font></a><font size=1 face="sans-serif">></font><font size=1 color=#5f5f5f face="sans-serif"><br>To: </font><font size=1 face="sans-serif">gpfsug
main discussion list <</font><a href="mailto:gpfsug-discuss@spectrumscale.org"><font size=1 color=blue face="sans-serif"><u>gpfsug-discuss@spectrumscale.org</u></font></a><font size=1 face="sans-serif">></font><font size=1 color=#5f5f5f face="sans-serif"><br>Date: </font><font size=1 face="sans-serif">10/29/2018
12:34 PM</font><font size=1 color=#5f5f5f face="sans-serif"><br>Subject: </font><font size=1 face="sans-serif">[gpfsug-discuss]
NSD network checksums (nsdCksumTraditional)</font><font size=1 color=#5f5f5f face="sans-serif"><br>Sent by: </font><a href="mailto:gpfsug-discuss-bounces@spectrumscale.org"><font size=1 color=blue face="sans-serif"><u>gpfsug-discuss-bounces@spectrumscale.org</u></font></a><font size=3><br></font><hr noshade><font size=3><br><br></font><tt><font size=2><br>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 </font></tt><a href="http://spectrumscale.org"><tt><font size=2 color=blue><u>spectrumscale.org</u></font></tt></a><font size=3 color=blue><u><br></u></font><a href="http://gpfsug.org/mailman/listinfo/gpfsug-discuss"><tt><font size=2 color=blue><u>http://gpfsug.org/mailman/listinfo/gpfsug-discuss</u></font></tt></a><tt><font size=2><br></font></tt><font size=3><br><br><br>_______________________________________________<br>gpfsug-discuss mailing list<br>gpfsug-discuss at </font><a href="http://spectrumscale.org"><font size=3 color=blue><u>spectrumscale.org</u></font></a><font size=3 color=blue><u><br></u></font><a href="http://gpfsug.org/mailman/listinfo/gpfsug-discuss"><font size=3 color=blue><u>http://gpfsug.org/mailman/listinfo/gpfsug-discuss</u></font></a><br><tt><font size=2>_______________________________________________<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></font></tt><br><BR>