Date: Fri, 17 Mar 2017 15:22:25 +0000 From: Matthew Seaman <matthew@FreeBSD.org> To: freebsd-questions@freebsd.org Subject: Re: bootable ext. USB SSD for backup Message-ID: <000a5cf9-36af-835f-d2f6-8dd3989260e8@FreeBSD.org> In-Reply-To: <15959.128.135.52.6.1489696154.squirrel@cosmo.uchicago.edu> References: <20170316194612.GA1748@c720-r314251> <33953.128.135.52.6.1489694167.squirrel@cosmo.uchicago.edu> <20170316211304.1c3481cc@archlinux.localdomain> <15959.128.135.52.6.1489696154.squirrel@cosmo.uchicago.edu>
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This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --MOKhjSRjiUa4DdU4TpbHxatAbRU25qlCT Content-Type: multipart/mixed; boundary="w7hEbOnCUVjncOd7QK4Cs42Vw55oojttu"; protected-headers="v1" From: Matthew Seaman <matthew@FreeBSD.org> To: freebsd-questions@freebsd.org Message-ID: <000a5cf9-36af-835f-d2f6-8dd3989260e8@FreeBSD.org> Subject: Re: bootable ext. USB SSD for backup References: <20170316194612.GA1748@c720-r314251> <33953.128.135.52.6.1489694167.squirrel@cosmo.uchicago.edu> <20170316211304.1c3481cc@archlinux.localdomain> <15959.128.135.52.6.1489696154.squirrel@cosmo.uchicago.edu> In-Reply-To: <15959.128.135.52.6.1489696154.squirrel@cosmo.uchicago.edu> --w7hEbOnCUVjncOd7QK4Cs42Vw55oojttu Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: quoted-printable On 2017/03/16 20:29, Valeri Galtsev wrote: > On Thu, March 16, 2017 3:13 pm, Ralf Mardorf via freebsd-questions wrot= e: >> On Thu, 16 Mar 2017 14:56:07 -0500 (CDT), Valeri Galtsev wrote: >>> Junior programmer faithfully thinks that one kilobyte is exactly 1000= >>> bytes. >>> >>> Senior programmer faithfully thinks that one kilogram is exactly 1024= >>> grams. >> When I programmed Commodore 64 Assembler a KB was 1024 B, nowadays I >> call it a KiB, to distinguish between 2^10 and 10^3, see >> https://en.wikipedia.org/wiki/Kibibyte . >> >> I dislike this joke, since senior programmers usually are also senior >> electronics technicians, > Right, I've heard the joke in a different language, so I had to make up= > some equivalent for "computer geek" and otherwise person. Sysadmin does= n't > fit there too as,e.g. myself, I have two degrees: electical engineering= > and computer science, so megaohms, and kilovolts are kind of there. So,= I > don't know what to call the person so torn off the real life (as I hear= d > the joke in metric based country, where "kilo-" is used everywhere). I, for one, welcome our new SI / NIST overlords. But then I started out as a scientist, and the fact the the SI prefixes (p n =B5 m 1 k M G P etc.) always indicate powers of 10^3 is engraved on my soul. For anyone unclear as to why this is a good idea, consider the statement: "we peaked at 1.1Gb/s transfer rate." That's computery stuff right? So it really means 1181116006.4b/s doesn't it? Nope. Bandwidth has always been measured in strict SI units -- mostly because it was physicists, electrical engineers and radio technicians got there first, and there's the Fourier relation between 'bits (samples) per second' and 'maximum signal frequency' that makes no sense at all if you start throwing powers of 2^10 around. (Google for 'Nyquist sampling theorem' if you're interested). Now work out how long it's going to take to transmit 10GB of data (assume packet overhead is already included...) at that rate. Easy enough (remember that 1B (byte) =3D 8b (bits) though.) Or did I mean 10Gi= B of data? It's this sort of confusion that leads to embarrassing mistakes like your Mars orbiter enjoying some unscheduled lithobraking[*]. And, for an encore, if anyone could bring me the head of what ever bright spark in Electricity generation thought that the bastard mongrel of a unit 'kWh' was a good idea, I'd be forever in your debt. It's a daft unit, when there is a perfectly acceptable and rigorous SI alternative which is even right around the same order of magnitude: the MegaJoule. 1 kWh is 3.6 MJ. Cheers, Matthew [*] OK, that was down to American Imperial vs SI units, but that is exactly the same sort of stupidity. --w7hEbOnCUVjncOd7QK4Cs42Vw55oojttu-- --MOKhjSRjiUa4DdU4TpbHxatAbRU25qlCT Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Comment: GPGTools - https://gpgtools.org iQJ8BAEBCgBmBQJYy/82XxSAAAAAAC4AKGlzc3Vlci1mcHJAbm90YXRpb25zLm9w ZW5wZ3AuZmlmdGhob3JzZW1hbi5uZXQxOUYxNTRFQ0JGMTEyRTUwNTQ0RTNGMzAw MDUxM0YxMEUwQTlFNEU3AAoJEABRPxDgqeTnqMwQAIxQTOBoCVA3vBrWp3MS4Y0D a0uj+iG5UZCobtLcdruo4loCxCy3zfJcjaHfABQte2m0dPCpKSadkWMVAEzTFfTp Ole/2wNhTlor2s+TLD9Ux413fLe4xmUe6kyO4eOdfJr/CsmID0vHOvcHKqNODA+l N9wgai9iG+6WNIHhBmMDqSvaxA/bGlgSWgVtLSIGL9rqr607sHp10GZFbDeEH+FW l49MF2ULVL39yaY8gb+4zu5RzjTxD2KH+3qeYYtA+DOogh1PGZsbVVQLMmPNDR+s QidfRHyPXeVoo6ZQOpTbMa8E4i/+cdHpk9cehGsd7/EsiJuJJQW4GmE9QqfdfBle ncknOMt73t/QAN5ZMKJAoWtE+GEwVfUbghnikwrVw2Sk9XX/4QBFwd5cGmK63Zu2 Ts3YGBJILzg3Y0g/egaGB9pi/9sP9x6bdby3XujDi8wIWzX/Uyl6sTMDdocZJosK oEB0RWSxXQHjmZgOn7tsm0mUkMDhBpip/aJ3oJWlgsPNFbkdrzIBK15Zs9TGWdhu Q53zxCV3Wz/w1DbxUUEWV1WqWkPmGcIT6s1sWocRbPpy+5TAYz9+QKC0BuC3uL21 49S3/EWuPLo1kNYs0qhP31DTDr1fCLq8himnO2BkbgXeTpVKrpaWuBvuRF+6zLPh oZVQPJ0e2zPXz18k0Y4V =sieo -----END PGP SIGNATURE----- --MOKhjSRjiUa4DdU4TpbHxatAbRU25qlCT--
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