| Jeff Abrahamson on 3 Dec 2005 14:41:07 -0000 |
|
On Thu, Dec 01, 2005 at 06:43:30PM -0500, Cosmin Nicolaescu wrote:
> cd /
> tar --exclude "./proc" --exclude "./PATH_TO_WHERE_YOU_MOUNT_SECOND_DRIVE"
> --exclude "./sys" --exclude "./tmp" --exclude "./WHATEVER ELSE YOU DON'T
> CARE" /PATH_TO_WHERE_YOU_MOUNT_SECOND_DRIVE .
If your install includes real user data and you are in the least
paranoid, it's worth rsync'ing the whole when you are done. There is
an exceedingly small chance of copy error on any copy. (Yes, there
are hardware and network parity bits, but one still expects a bad byte
or block every few billion or something like that.) Rsync will do
real checksums and so confirm and fix the integrity of the copy.
Alternatively, do something like
find / -exec sha1sum \{\} \; > /tmp/sha1sum
on each machine and diff the two files.
Copy 200 GB drives regularly and it will crop up. Why don't we hear
about this? Because most people never check and so the error goes
unnoticed. If I modify one block of one file on your drive, that file
is probably toast, but how long until you notice?
Anecdote: I went to a talk by a guy from AT&T. They have an enormous
amount of billing info each day, so much so that it's a challenger to
process it all in a day. They actually used flat file databases
because Oracle and its ilk just weren't fast enough on such large
databases. (By the time oracle indexed today's data, there wasn't
time to process today's data, and then tomorrow's data was arriving,
or something like that.)
Anyway, they found a bug in SunOS where every 50e6 pages or something
like that the kernel would swap two pages.
--
Jeff
Jeff Abrahamson <http://www.purple.com/jeff/> +1 215/837-2287
GPG fingerprint: 1A1A BA95 D082 A558 A276 63C6 16BF 8C4C 0D1D AE4B
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