Path: csiph.com!usenet.pasdenom.info!weretis.net!feeder4.news.weretis.net!storethat.news.telefonica.de!telefonica.de!news-1.dfn.de!news.dfn.de!fu-berlin.de!uni-berlin.de!individual.net!not-for-mail From: Ian Collins Newsgroups: comp.programming Subject: Re: Do integrity checks by file comparison really work? Date: Sat, 19 Jan 2013 17:12:24 +1300 Lines: 22 Message-ID: References: <50ec0b68$0$17952$4fafbaef@reader1.news.tin.it> <50f68341$0$13278$4fafbaef@reader2.news.tin.it> <3ldjf892v9a6cfbprr4qirpgchkj9sg2ev@4ax.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Trace: individual.net pn26p1FY5PUSiH32ESyWyw5IHOAchHPAes0nWPMxrtDECCuFZVd5R7FCocRziy6DZt Cancel-Lock: sha1:zbYEVhI5r9ysKpMj/tub1VDQCUI= User-Agent: Mozilla/5.0 (X11; SunOS i86pc; rv:17.0) Gecko/17.0 Thunderbird/17.0 In-Reply-To: <3ldjf892v9a6cfbprr4qirpgchkj9sg2ev@4ax.com> Xref: csiph.com comp.programming:2863 Robert Wessel wrote: > On Wed, 16 Jan 2013 11:38:54 +0100, Thomas B > wrote: >> >> You wrote: "I've never seen an OS that would share file buffers between >> two files like that", so I suppose this should be the same for files on >> the same volume. > > > Some OS's/filesystems can do a copy with the equivalent of a *nix hard > link, and then do a copy-on-write procedure if the file is ever > modified. In that case you may have only a single copy of the file. > It can't do that to you across volumes. ZFS is a good example. If you snapshot or clone a filesystem, no extra space is used until it (a clone) or the source are modified. ZFS also checksums its data, so there is no need to use another tool to validate copes. -- Ian Collins