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I have a SQL system that is doing a large amount of reads to disk at a throughput rate of about 1GB/s at times. During the time there is a lot of disk activity, the ISCSI is translated to over 8GB/s of network receive activity. in this scenario we are using Jumbo frames, so I would assume that there is about 99.1% of efficiency, and we are certainly not seeing that.

Setup: HPE 3PAR SAN VMware virtual machine with dedicated 10GB virtual adapter for ISCSI All the recommended advanced network adapter settings are set on the NIC Using the in-guest Microsoft ISCSI initiator driver and setup - no 3rd party tools We are set up with ISCSI MPIO (round robin with subset) from the single Client side ISCSI IP to two 10GB Array side ISCSI IP/IQNs

Can anyone think of why the Disk reads would be causing such a large amount of Network traffic?

BrowniePoints88
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  • Note that while I did answer the question because I found it interesting, this question is completely and utterly off-topic here, and will be downvoted into oblivion, closed, deleted, and nuked from orbit in the blink of an eye. Please, take the [tour], learn [ask] a good question, and read the [FAQ] and the [help]. If you are unsure whether a question is on-topic, you can always ask in [chat] or on [meta]. – Jörg W Mittag Apr 30 '20 at 14:02
  • Thanks! I certainly appreciate you taking the time to answering an off topic question. – BrowniePoints88 May 01 '20 at 16:44

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Normally, disks are measured in Bytes (more precisely, Octets) and networks are measured in Bits. Since there is no international standard for those units, it is usually advised to never abbreviate them. In particular, both Byte and Bit are commonly abbreviated as "B", and it is assumed that the meaning is clear from context (e.g. when talking about storage, we never talked about Bits, when talking about networks, we generally talk about Bits).

So, a throughput of 1 GByte/s on the disk is 8 Gbit/s, which matches pretty much exactly what you are seeing on the network.

Jörg W Mittag
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  • That is true, and I thought of that being a possible reason for what I was seeing, but i couldn't quite tell what Resource Monitor was telling me. I see "1111 MB/Sec Disk I/O" translating to 9-10 "Gbps Network I/O" So, I think you may be right - does it sound like I am just reading the units wrong with that description? – BrowniePoints88 Apr 30 '20 at 14:30