Other Explanation sought for camcontrol output

byrnejb

byrnejb

We have an older eight-bay supermicro system. Four of the bays contain the 3Tb hdds allocated to our raidz2 zpool. Two of the other four are empty and the remaining two contain a 1TB and a 3TB drive. I have swapped the 3Tb drive from one bay to another with the follwoing results:

Original:
Code: 
[root@vhost03 ~ (master)]# camcontrol devlist
<ATA WDC WD30EFRX-68A 0A80>        at scbus0 target 0 lun 0 (da1,pass6)
<ATA WDC WD1002FAEX-0 1D05>        at scbus0 target 1 lun 0 (da0,pass0)
<WDC WD30EFRX-68AX9N0 80.00A80>    at scbus1 target 0 lun 0 (ada0,pass1)
<WDC WD30EFRX-68AX9N0 80.00A80>    at scbus2 target 0 lun 0 (pass2,ada1)
<WDC WD30EFRX-68AX9N0 80.00A80>    at scbus3 target 0 lun 0 (pass3,ada2)
<WDC WD30EFRX-68AX9N0 80.00A80>    at scbus4 target 0 lun 0 (pass4,ada3)
<AHCI SGPIO Enclosure 2.00 0001>   at scbus7 target 0 lun 0 (ses0,pass5)

After swap:
Code: 
[root@vhost03 ~ (master)]# camcontrol devlist
<ATA WDC WD1002FAEX-0 1D05>        at scbus0 target 1 lun 0 (da1,pass6)
<ATA WDC WD30EFRX-68A 0A80>        at scbus0 target 2 lun 0 (da0,pass0)
<WDC WD30EFRX-68AX9N0 80.00A80>    at scbus1 target 0 lun 0 (ada0,pass1)
<WDC WD30EFRX-68AX9N0 80.00A80>    at scbus2 target 0 lun 0 (pass2,ada1)
<WDC WD30EFRX-68AX9N0 80.00A80>    at scbus3 target 0 lun 0 (pass3,ada2)
<WDC WD30EFRX-68AX9N0 80.00A80>    at scbus4 target 0 lun 0 (pass4,ada3)
<AHCI SGPIO Enclosure 2.00 0001>   at scbus7 target 0 lun 0 (ses0,pass5)

I can see that the 3TB WD moved from scbus0 target 0 lun 0 (da1,pass6) to scbus0 target 2 lun 0 (da0,pass0). What I need interpreted is what is the difference between the ada and da devices insofar as FreeBSD is concerned? Why are four of the 3Tb drives adas but the remaining one is a da?
 
Start by looking a man ada and man da: The ada driver is for ATA disks (also known as IDE or SATA), while the da driver is for SCSI disks.

Now in your case, the hardware WDC disks are not actually SCSI disks. That means that somewhere in the data path is an ATA-to-SCSI converter. Since you're using a backplane, that converter could be in the backplane, or it could be in small daughter cards installed on the disks or on the caddy, or it could be that certain slots of your backplane are connected to a different HDA (or disk port, on motherboard or extension card) which automatically converts the protocol from ATA to SCSI.

What difference does it make in practice?

If you're using smart, you may have to configure it correctly to get through the ATA-to-SCSI converter, but sometimes that is automatic.
 
SATA drives connected through SAS HBA would show as da, won't they? I remember some pretty cut-down on-board SAS controller on X9 that was used to connect drives in front disk bay.
 
SirDice said:
Edit: Well, I guessed wrong. Checked the drives types and they all should be SATA. They might be connected to different controllers though, https://forums.freebsd.org/threads/freebsd-does-not-find-two-out-of-eight-chassis-slots.85905/
Click to expand...
Yes, this is the same device. However, it does not seem to matter which of the unused bays I put the hdd, it never appears as an ata. There appear to be six on one controller and two on the other. Drives in those two continually show a blinking red light. The same drives moved to the other unused bays do not blink.
 
yuripv79 said:
SATA drives connected through SAS HBA would show as da, won't they?
Click to expand...
Indeed. I actually have several SATA disks on a SAS controller and they're all da*, I should have double checked.
 
The unit is a 5027R-ERF superserver. This is what the manual says:
SATA
A SATA controller is integrated into the chipset to provide a six-port, SATA subsys-
tem, which is RAID 0, 1, 5 and 10 supported. The SATA drives are hot-swappable
units. Two of the ports support SATA 3.0 (6 Gb/s) while the other four are SATA
2.0 (3 Gb/s) ports.
Note: You must have RAID set up to enable the hot-swap capability of the SATA
drives. Documentation on RAID setup guidelines can be found on our web site.
SCU SATA
An additional SCU SATA controller integrated into the chipset provides four SATA 2
ports. RAID 0, 1 and 10 are supported. The SATA drives are hot-swappable units.
Note: You must have RAID set up to enable the hot-swap capability of the SATA
drives. Documentation on RAID setup guidelines can be found on our web site.

According to the manual bays 0 through 3 are located on the lower row numbered from left to right as viewed from the front panel. Bays 4 through 8 are on the top row, again numbered from left to right. Bays 7 and 8 are the bays that make the drive blink with a red led.
 
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