On Sep 30, 2010, at 15:40 , Gary Buhrmaster wrote: > On Thu, Sep 30, 2010 at 05:19, Stephan Wiesand <[email protected]> > wrote: > ... > >> Anyway, the next best option if ZFS is not available is to run parity checks >> on all your arrays regularly. > > Perhaps it is the best one can do, but be aware that > a (rare, but real) failure mode of disks is that they > return the contents of a different block than asked.
I know :-) > No amount of background scrubbing fixes that > unless the failures are solid (and they are usually > not). As I said: my experience is that a disk either does it or not. If it does, it does so when it's new and shiny. But yes, I'd still like to have ZFS's data protection. > That does not even include the issue that > most disk controller data paths (and cache > memories) are not even parity checked, and > bit flipping can happen there too. right :-( > NetApp recognized this and dealt with it with > the WAFL file system years ago. They actually > wrote a checksum for the block and the block id > onto disk and checked when they read a block > back. > > Getting back the data your wrote is a hard > problem. ZFS presumes that everything > downstream of it will (eventually) fail. There > is overhead there, but it does solve a set > of problems that other solutions do not. > (And the highly paranoid presume ZFS will > fail, so take different precautions). > > As Jeff stated, if you really care about your > data, you need ZFS. > Gary Alas, ZFS is only available with an OS that's *really* troublesome to maintain. Frankly, I wouldn't mind the cost. But those patch orgies make Solaris a no-go here. And two decades after the invention of RPMS and DEBs, they come up with ... IPS. Sorry, no matter how good and exceptional ZFS may be, it's just not worth it... Stephan -- Stephan Wiesand DESY -DV- Platanenenallee 6 15738 Zeuthen, Germany
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