Hi, >>How can it be that the I/O performance degradation warning only seems to accompany the nsdCksumTraditional setting and not GNR? >>Why is there such a penalty for "traditional" environments?
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. 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). My two cents. Regards, -Kums From: Aaron Knister <[email protected]> To: gpfsug main discussion list <[email protected]> Date: 10/29/2018 12:34 PM Subject: [gpfsug-discuss] NSD network checksums (nsdCksumTraditional) Sent by: [email protected] Flipping through the slides from the recent SSUG meeting I noticed that in 5.0.2 one of the features mentioned was the nsdCksumTraditional flag. Reading up on it it seems as though it comes with a warning about significant I/O performance degradation and increase in CPU usage. I also recall that data integrity checking is performed by default with GNR. How can it be that the I/O performance degradation warning only seems to accompany the nsdCksumTraditional setting and not GNR? As someone who knows exactly 0 of the implementation details, I'm just naively assuming that the checksum are being generated (in the same way?) in both cases and transferred to the NSD server. Why is there such a penalty for "traditional" environments? -Aaron -- Aaron Knister NASA Center for Climate Simulation (Code 606.2) Goddard Space Flight Center (301) 286-2776 _______________________________________________ gpfsug-discuss mailing list gpfsug-discuss at spectrumscale.org http://gpfsug.org/mailman/listinfo/gpfsug-discuss
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