Hacker News Reader

Hacker News

Comment by MR4D | Hacker News Reader

Parent Full thread

MR4D

How can we find this information out easily (not just for Samsung, but for others)?

Even Anandtech only tested 32 queues on the 980 Pro [0].

[0] - https://www.anandtech.com/show/16087/the-samsung-980-pro-pci...

View on HN

Number of queues is not the same as the number of operations in a queue.

Supporting more queues means that you need less communication and synchronization between CPU cores; ideally, you have at least one queue per core so that each CPU core can submit commands to the SSD independently.

I didn't test queue depths higher than 32 when I reviewed the 980 PRO, because it's a consumer drive and consumer workloads hardly ever produce double-digit queue depths. Even going all the way up to QD32 is fairly unrealistic.

Server workloads can be quite different, and some of them genuinely can result in a large number of simultaneous IO requests. Consumer workloads have barely even started to evolve to take advantage of SSDs, and hard drives aren't quite entirely gone from the consumer PC market.

As for how to check how many queues a NVMe drive supports: the easy way is to install the drive in a system with a very large number of CPU cores, and see how many queues the Linux NVMe driver creates (check the drive's sysfs directory). My understanding from reading the NVMe spec is that you can't necessarily query the drive itself for the number of supported queues after the operating system's NVMe driver has already done that and set up its queues.

Is this not the correct way to do it?

  $ sudo nvme get-feature /dev/nvme0 -f 7
  get-feature:0x7 (Number of Queues), Current value:0x7f007f

That's the number of queues requested by the host system. If you ran that on a system with four CPU cores (and no SMT), you'd likely see that same drive return 4 instead of 7.

Set-feature for that value is how the host system indicates how many queues it is requesting. A subsequent get-feature returns how many queues were actually allocated. This can be less than the maximum supported by the drive, such as if the OS didn't request very many queues (due to you not having very many CPU cores), or if the drive is being virtualized and some of its queues are already allocated to a different virtual function.

>Consumer workloads have barely even started to evolve to take advantage of SSDs, and hard drives aren't quite entirely gone from the consumer PC market.

I really wish there is some industry push towards this. But last time ( I think around 6-7 years ago ) I try to push for this the answer was Information Security and Data erase / recovery would not allow SSD to be used in certain industry and domain. It has to be HDD.

I wonder if this has changed in the era of Smartphone and Tablet where NAND are now the default solution.

The latest generation of video game consoles come with NVMe SSDs as standard components, and game developers are starting to target solid state storage as a baseline requirement. So there's some visible progress, with support from GPU hardware vendors, and Microsoft bringing new storage APIs to the table (including a clone of io_uring).

I think any security concerns that might have once privileged hard drives over SSDs have been settled. There are plenty of options for FIPS 140-2/3 certified self-encrypting drives, and broad support for Sanitize operations that instruct the drive to wipe all user data even from storage areas that may not be accessible to the host system (ie caches, spare blocks. Any holdouts still preferring hard drives for security reasons are most probably deluded, and certainly are not influencing the storage market in any meaningful way.

Reply on news.ycombinator.com