When dealing with disks and I/O things on Linux, you’d regularly run commands like lsblk, lsscsi, nvme list, etc. All of them tend to report a different set of information, so I ended up running multiple commands and correlating their output based on the device name or number.

And then I had to run commands like these, to get extra info about the current OS-level configuration settings for specific disks:

grep . /sys/class/block/sd*/device/queue_depth
grep . /sys/class/block/*/queue/nr_requests

The above commands would show the hardware-advertised device queue depth and the OS block device level (software) queue depth.

I finally had enough and created a single Python program lsds for showing all interesting bits for a disk in one place. The lsds tool does not execute any other commands under the hood, it just reads the relevant info from sysfs /sys/class/blocks/... directories directly.

See my 0x.tools toolset for more Linux performance & troubleshooting tools.

Here’s an output from my machine with 21 SSDs in it. You may need to scroll right to see the full output:

$ lsds
DEVNAME   MAJ:MIN  SIZE        TYPE      SCHED  ROT  MODEL                       QDEPTH  NR_RQ  WCACHE       
nvme0n1   259:4    931.5 GiB   NVMeDisk  none   0    Samsung SSD 9100 PRO 1TB    -       1023   write back   
nvme10n1  259:21   465.8 GiB   NVMeDisk  none   0    Samsung SSD 980 PRO 500GB   -       1023   write back   
nvme11n1  259:22   465.8 GiB   NVMeDisk  none   0    Samsung SSD 980 PRO 500GB   -       1023   write back   
nvme12n1  259:9    931.5 GiB   NVMeDisk  none   0    Samsung SSD 980 PRO 1TB     -       1023   write back   
nvme13n1  259:16   931.5 GiB   NVMeDisk  none   0    Samsung SSD 980 PRO 1TB     -       1023   write back   
nvme14n1  259:8    931.5 GiB   NVMeDisk  none   0    Samsung SSD 980 PRO 1TB     -       1023   write back   
nvme15n1  259:15   931.5 GiB   NVMeDisk  none   0    Samsung SSD 980 PRO 1TB     -       1023   write back   
nvme16n1  259:12   1863.0 GiB  NVMeDisk  none   0    T-FORCE TM8FF1002T          -       1023   write back   
nvme17n1  259:11   1863.0 GiB  NVMeDisk  none   0    T-FORCE TM8FF1002T          -       1023   write back   
nvme18n1  259:13   1863.0 GiB  NVMeDisk  none   0    T-FORCE TM8FF1002T          -       1023   write back   
nvme19n1  259:14   1863.0 GiB  NVMeDisk  none   0    T-FORCE TM8FF1002T          -       1023   write back   
nvme1n1   259:1    931.5 GiB   NVMeDisk  none   0    Samsung SSD 9100 PRO 1TB    -       1023   write back   
nvme20n1  259:3    1863.0 GiB  NVMeDisk  none   0    Samsung SSD 990 PRO 2TB     -       1023   write back   
nvme2n1   259:2    931.5 GiB   NVMeDisk  none   0    Samsung SSD 9100 PRO 1TB    -       1023   write back   
nvme3n1   259:0    931.5 GiB   NVMeDisk  none   0    Samsung SSD 9100 PRO 1TB    -       1023   write back   
nvme4n1   259:18   931.5 GiB   NVMeDisk  none   0    Samsung SSD 980 PRO 1TB     -       1023   write back   
nvme5n1   259:23   931.5 GiB   NVMeDisk  none   0    Samsung SSD 980 PRO 1TB     -       1023   write back   
nvme6n1   259:19   931.5 GiB   NVMeDisk  none   0    Samsung SSD 980 PRO 1TB     -       1023   write back   
nvme7n1   259:20   931.5 GiB   NVMeDisk  none   0    Samsung SSD 980 PRO 1TB     -       1023   write back   
nvme8n1   259:17   1788.5 GiB  NVMeDisk  none   0    SAMSUNG MZQL21T9HCJR-00A07  -       1023   write through
nvme9n1   259:10   1397.3 GiB  NVMeDisk  none   0    INTEL SSDPE21D015TA         -       1023   write through

All the above disks are NVMe SSDs, so the I/O scheduler (SCHED) is “none” and the rotational flag (ROT) is 0.

If you prefer narrower pivoted output, you can use the --pivot option as you see below. I also added the --verbose flag to explain where this tool got its information from:

$ lsds -pv
DEVNAME      NAME         VALUE
nvme0n1      MAJ:MIN      259:4                     /sys/class/block/nvme0n1/dev
nvme0n1      SIZE         931.5 GiB                 /sys/class/block/nvme0n1/size * 512
nvme0n1      TYPE         NVMeDisk                  devname, /sys/class/block/nvme0n1/partition
nvme0n1      SCHED        none                      /sys/class/block/nvme0n1/queue/scheduler
nvme0n1      ROT          0                         /sys/class/block/nvme0n1/queue/rotational
nvme0n1      MODEL        Samsung SSD 9100 PRO 1TB  /sys/class/block/nvme0n1/device/model
nvme0n1      QDEPTH       -                         /sys/class/block/nvme0n1/device/queue_depth (N/A for NVMe)
nvme0n1      NR_RQ        1023                      /sys/class/block/nvme0n1/queue/nr_requests
nvme0n1      WCACHE       write back                /sys/class/block/nvme0n1/queue/write_cache

...

nvme9n1      MAJ:MIN      259:10                    /sys/class/block/nvme9n1/dev
nvme9n1      SIZE         1397.3 GiB                /sys/class/block/nvme9n1/size * 512
nvme9n1      TYPE         NVMeDisk                  devname, /sys/class/block/nvme9n1/partition
nvme9n1      SCHED        none                      /sys/class/block/nvme9n1/queue/scheduler
nvme9n1      ROT          0                         /sys/class/block/nvme9n1/queue/rotational
nvme9n1      MODEL        INTEL SSDPE21D015TA       /sys/class/block/nvme9n1/device/model
nvme9n1      QDEPTH       -                         /sys/class/block/nvme9n1/device/queue_depth (N/A for NVMe)
nvme9n1      NR_RQ        1023                      /sys/class/block/nvme9n1/queue/nr_requests
nvme9n1      WCACHE       write through             /sys/class/block/nvme9n1/q