bootable ext. USB SSD for backup
smithi at nimnet.asn.au
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 unixarea.de> 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
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.
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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