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storagepciscsi
Harish Basavaraju
Harish Basavaraju

Reputation: 67

Difference between NVMe queuing interface and PCIe queuing interface

Can any please let me know the difference between the two.

Please provoide relavent links if any .

Upvotes: 0

Views: 648

Answers (2)

Alex Guteniev
Alex Guteniev

Reputation: 13719

PCIe Queuing Interface (PQI) was a storage protocol with queues, similar to NVMe.

Nowadays NVMe thrives, and PQI is dead.

Some differences are:

  • NVMe defines both queues organization and command sets. PQI defines only queues organization, entries in this queue are arbitrary. It had an upper-level protocol to carry SCSI commands over it, which was defined separately (called SOP - SCSI over PQI)
  • NVMe uses fixed size command entries with uniform layout, one per queue slot. PQI could use multiple queue slots for one command
  • PQI used producer and consumer indices, they were similar to NVMe doorbells in some sense, but required more operations to service a command
  • NVMe employs PRPs to address data, later on SGLs were added as an alternative, PQI used SGLs only from the start

Upvotes: 0

gayle noble
gayle noble

Reputation: 1

I'm just learning this stuff but from what I am reading: The maximum size of the Admin Completion Queue is 4096 entries. This is a 0’s based value. The maximum size of the Admin Submission Queue is 4096 entries. This is a 0’s based value. (NVM-Express 1.1)

however The maximum number of elements is 255 for administrator IQs and administrator OQs. http://www.t10.org/cgi-bin/ac.pl

so I am sure there are lots of other differences

Upvotes: 0

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