can you guess? wrote: ... > Ah - thanks to both of you. My own knowledge of video format internals > is so limited that I assumed most people here would be at least equally > familiar with the notion that a flipped bit or two in a video would > hardly qualify as any kind of disaster (or often even as being > noticeable, unless one were searching for it, in the case of > commercial-quality video). > > David's comment about jpeg corruption would be more worrisome if it were > clear that any significant number of 'consumers' (the immediate subject > of my original comment in this area) had anything approaching 1 TB of > jpegs on their systems (which at an average of 1 MB per jpeg would be > around a million pictures...). If you include 'image files of various > sorts', as he did (though this also raises the question of whether we're > still talking about 'consumers'), then you also have to specify exactly > how damaging single-bit errors are to those various 'sorts' (one might > guess not very for the uncompressed formats that might well be taking up > most of the space). And since the CERN study seems to suggest that the > vast majority of errors likely to be encountered at this level of > incidence (and which could be caught by ZFS) are *detectable* errors, > they'll (in the unlikely event that you encounter them at all) typically > only result in requiring use of a RAID (or backup) copy (surely one > wouldn't be entrusting data of any real value to a single disk).
I have to comment here. As a bloke with a bit of a photography habit - I have a 10Mpx camera and I shoot in RAW mode - it is very, very easy to acquire 1Tb of image files in short order. Each of the photos I take is between 8 and 11Mb, and if I'm at a sporting event or I'm travelling for work or pleasure, it is *incredibly* easy to amass several hundred Mb of photos every single day. I'm by no means a professional photographer (so I'm not out taking photos every single day), although a very close friend of mine is. My photo storage is protected by ZFS with mirroring and backups to dvd media. My profotog friend has 3 copies of all her data - working set, immediate copy on usb-attached disk, and second backup also on usb-attached disk but disconnected. Even if you've got your original file archived, you still need your working copies available, and Adobe Photoshop can turn that RAW file into a PSD of nearly 60Mb in some cases. It is very easy for the storage medium to acquire some degree of corruption - whether it's a CF or SD card, they all use FAT32. I have been in the position of losing photos due to this. Not many - perhaps a dozen over the course of 12 months. That flipped bit which you seem to be dismissing as "hardly... a disaster" can in fact make your photo file totally useless, because not only will you probably not be able to get the file off the media card, but whatever software you're using to keep track of your catalog will also be unable to show you the entire contents. That might be the image itself, or it might be the equally important EXIF information. I don't depend on FAT32-formatted media cards to make my living, fortunately, but if I did I imagine I'd probably end up only using each card for about a month before exercising caution and purchasing a new one rather than depending on the card itself to be reliable any more. 1Tb of photos shot on a 10MPx camera in the camera's native RAW format is around 100,000 photos. It's not difficult to imagine a "consumer" having that sort of storage requirement. James C. McPherson -- Senior Kernel Software Engineer, Solaris Sun Microsystems http://blogs.sun.com/jmcp http://www.jmcp.homeunix.com/blog _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
