bootable ext. USB SSD for backup

Ian Smith smithi at
Fri Mar 17 13:07:06 UTC 2017

In freebsd-questions Digest, Vol 667, Issue 6, Message: 5
On Thu, 16 Mar 2017 20:46:12 +0100 Matthias Apitz <guru at> wrote:

 > I have acquired a small and flat USB 3.0 external disk (must be SSD for
 > the size of the case):
 > Mar 16 19:36:54 c720-r314251 kernel: da0: <TOSHIBA External USB 3.0 5438> Fixed Direct Access SPC-4 SCSI device
 > Mar 16 19:36:54 c720-r314251 kernel: da0: Serial Number 20170114010787F

Hi Matthias,

Can you give an URL to specs for this model?  I had a quick hunt and was 
amazed how fast prices have come down for big SSDs, so I'm interested.

 > Mar 16 19:36:54 c720-r314251 kernel: da0: 40.000MB/s transfers

That's on a USB 2.0 port, right?  For USB 3.0 it would say 400MB/s ..

 > Mar 16 19:36:54 c720-r314251 kernel: da0: 953869MB (1953525164 512 byte sectors)
 > Mar 16 19:36:54 c720-r314251 kernel: da0: quirks=0x2<NO_6_BYTE>
 > Ofc it has not the promised 1 TB volume, just only 953869 MB, i.e. only
 > 1 Marketing-TB;

Yeah, it's been that way for a decade or two .. even smartctl reports in 
10^x units, e.g. this is the '64GB' SSD that came with my Lenovo X200:

root at x200:~ # smartctl -i /dev/ada0 | egrep 'Model|Capacity|Sector|Rotation|ATA'
Device Model:     SAMSUNG MMCRE64G8MPP-0VA
User Capacity:    64,023,257,088 bytes [64.0 GB]
Sector Size:      512 bytes logical/physical
Rotation Rate:    Solid State Device
ATA Version is:   ATA/ATAPI-7 T13/1532D revision 1

root at x200:~ # echo 'scale=3; 64023257088 / 1024^3' | bc

If you have smartmontools installed, I'd be interested in seeing a 
'smartctl -Ai /dev/da0' for this device?  Offlist if you prefer.

 > I'm thinking in re-partitioning the disk (which is actual only one big
 > NTFS slice) with gpart(8), install even a kernel into a small FS at the
 > beginning and keep the rest as a big UFS for backups. Having it bootable
 > with a system could be handy if one has to rescue a system and restore
 > the last dunp.

Even 20GB would be 'small' on this; it could double as a spare system.

If it were me I'd more likely add, say, 3 x ~310GiB partitions, but I'd
be dumping a larger number of smaller FS, keeping several generations.

cheers, Ian

PS: there's been some fun - and some rather tedious - nonsense written 
on this thread, but if I were the judge, first prize must go to Warren:

 > (The memory units used above are actually gwibblybytes (GwB), 1012 
 > 7.9-bit bytes per kwibblybyte (KwB), 1011 KwB per mibblybyte (MwB), and 
 > 1010 MwB per gwibblybyte, or about fourteen thousandths short of a 
 > dwibblyliter (DwL).)

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