> > Here's one possible reason that a read-only ZFS would be useful: DVD-ROM > > distribution. > > built-in compression works for DVDs, too. > > > Sector errors on DVD are not uncommon. Writing a DVD in ZFS format with > > duplicated data blocks would help protect against that problem, at the cost > > of 50% or so disk space. That sounds like a lot, but with BluRay etc. > > coming along, maybe paying a 50% penalty isn't too bad. (And if ZFS > > eventually supports RAID on a single disk, the penalty would be less.) > > Also, traditionally, CD and DVD-ROMs have poor path data protection. > ZFS's end-to-end error checking is an advantage in such environments. > -- richard-who-barely-survived-a-flaky-CD-ROM-cable-incident
See my ZFSCD posts from earlier. ZFS currently doesn't support mounting from read-only volumes. I'd plead a case to consider temporary zpools, where ZFS doesn't even consider writing the in-use flags, which actually posed the problem in my tests, and mounts the filesystem as real read-only. But then again, who's going to burn ZFSCDs or ZFSDVDs in the short term (I would, but hit a roadblock)? I mean, there are a few nice benefits, which are the reason I tried this in the first place. Checksums, improved data integrity, escalator sorting aswell as ZFS prefetching. Especially the latter might be convenient for performance on CD/DVD drives, e.g. with applications that sequentially read data from discs, but instead of prefetching issue tons of small requests (virtually all audio and video players known to man). Also, where does this single disk RAID notion come from? This sounds actually interesting. Is this a project actually in progress or to be considered? Sure, it doesn't prevent data loss on disk failure, however may improve the safety of your data a lot without plain out losing half your disk space due to simple mirroring. -mg
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