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A notebook has only one SSD (without CDROM drive)

if I take a look at /proc/scsi/scsi it outpus:

Host: scsi2 Channel: 00 Id: 00 Lun: 00
  Vendor: ATA      Model: KINGSTON SUV500M Rev: 56RI
  Type:   Direct-Access                    ANSI  SCSI revision: 05

If I run lssci it results in:

[2:0:0:0]    disk    ATA      KINGSTON SUV500M 56RI  /dev/sda 

However lsscsi -H it outputs:

[0]    ahci          
[1]    ahci          
[2]    ahci 

why are 3 entries of ahci?

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1 Answer 1

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"Host" is the interface to which a SCSI device is attached, including interfaces like USB, which are not physical.

lsscsi reports the low level SCSI driver's name, i.e. the name of that interface. You find it under /sys/class/scsi_host/*/proc_name and /proc/scsi. I don't know if it has a practical use for system administrators.

On my server (ARM-based credit-card-sized thing), I have a USB disk with host "usb-storage". The usb-storage driver is compiled into my kernel, and I don't seem to have a usb-storage kernel module.

More reading:

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  • Nice information, I've reformulated my main question, but still I don't know why are 3 entries of ahci driver...
    – sebelk
    Commented Apr 26, 2021 at 0:55
  • Because you have three SCSI interfaces. Only one of them has a disk attached. Try lspci to see if there are more physical interfaces in your laptop. Or perhaps the driver needs to create hosts 0 and 1 for some reason, or some other kernel component, or perhaps udev. The kernel startup messages may shed some light on this. Commented Apr 26, 2021 at 1:04
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    dmesg on an old Thinkpad tells me: ahci 0000:00:1f.2: AHCI 0001.0300 32 slots 6 ports 6 Gbps 0x13 impl SATA mode. I interpret this as one interface with six ports, and wouldn't you know, lsscsi -H reports six ahci interfaces. I learned something :) Commented Apr 26, 2021 at 1:10

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