ada vs. da?

[Jack L.]

ada and da are different. Your ada's are your atapi disk devices
(sata). The da's are direct attached (usb sticks and scsi devices)
which show as not attached.

On Sun, Aug 13, 2017 at 9:55 PM, Mikhail T. <mi+thun at aldan.algebra.com> wrote:
> The four AHCI-drives in my system appear as both adaX and daX each:
>
>    <ST3000DM001-1CH166 CC43>          at scbus2 target 0 lun 0 (ada1,pass2)
>    <ST3000DM001-1CH166 CC43>          at scbus3 target 0 lun 0 (ada2,pass3)
>    <ST3000DM001-1CH166 CC43>          at scbus5 target 0 lun 0 (ada3,pass4)
>    <ST3000DM001-1CH166 CC43>          at scbus6 target 0 lun 0 (ada4,pass5)
>    <Generic STORAGE DEVICE 0550>      at scbus7 target 0 lun 0 (da0,pass6)
>    <Generic STORAGE DEVICE 0550>      at scbus7 target 0 lun 1 (da1,pass7)
>    <Generic STORAGE DEVICE 0550>      at scbus7 target 0 lun 2 (da2,pass8)
>    <Generic STORAGE DEVICE 0550>      at scbus7 target 0 lun 3 (da3,pass9)
>
> Each one is listed in /var/run/dmesg.boot like this:
>
>    ada2: <ST3000DM001-1CH166 CC43> ATA8-ACS SATA 3.x device
>    ada2: Serial Number Z1F1E8NK
>    ada2: 300.000MB/s transfers (SATA 2.x, UDMA6, PIO 8192bytes)
>    ada2: Command Queueing enabled
>    ada2: 2861588MB (5860533168 512 byte sectors)
>    ada2: quirks=0x1<4K>
>    ada2: Previously was known as ad8
>    da2: <Generic STORAGE DEVICE 0550> Removable Direct Access SPC-3
>    SCSI device
>    da2: Serial Number 000000000195
>    da2: 40.000MB/s transfers
>    da2: Attempt to query device size failed: NOT READY, Medium not present
>    da2: quirks=0x3<NO_SYNC_CACHE,NO_6_BYTE>
>
> What am I supposed to make of it? Can they be accessed through either name?
> What are the advantages of each? If ada is always a better choice, how do I
> make the da ones disappear -- such as from the systat's output? Thanks!
>
>    -mi
>
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