2006/1/17, Michael Tokarev <mjt@xxxxxxxxxx>: > Sander wrote: > This is about code complexity/bloat. It's already complex enouth. > I rely on the stability of the linux softraid subsystem, and want > it to be reliable. Adding more features, especially non-trivial > ones, does not buy you bugfree raid subsystem, just the opposite: > it will have more chances to crash, to eat your data etc, and will > be harder in finding/fixing bugs. > > Raid code is already too fragile, i'm afraid "simple" I/O errors > (which is what we need raid for) may crash the system already, and > am waiting for the next whole system crash due to eg superblock > update error or whatnot. I saw all sorts of failures due to > linux softraid already (we use it here alot), including ones > which required complete array rebuild with heavy data loss. > > Any "unnecessary bloat" (note the quotes: I understand some > people like this and other features) makes whole system even > more fragile than it is already. > > Compare this with my statement about "offline" "reshaper" above: > separate userspace (easier to write/debug compared with kernel > space) program which operates on an inactive array (no locking > needed, no need to worry about other I/O operations going to the > array at the time of reshaping etc), with an ability to plan it's > I/O strategy in alot more efficient and safer way... Yes this > apprpach has one downside: the array has to be inactive. But in > my opinion it's worth it, compared to more possibilities to lose > your data, even if you do NOT use that feature at all... > > /mjt I do agree with you about that : the lesser the code, the fewer the bugs. Of course. But I do think that Linux would not have become what it is now if each-and-every new feature was debated for years and years about their risk. Anyway, having a suspiously bogus raid5 resize is not a fatality : what about having a 'paranoïd' option/strategy, decreasing performance but mirroring superblocks on another device (not necessarily on the array), logging/journalling loads of stuff (metadata quite exclusively), and making resize much much stronger ? I prefer having my raid5 online and have a resize time of 12 hours than putting it offline and have a resize time of 2 hours. This is not marketting, this is the way computers shall behave :-p. Trustworthy features and flexibility in the same box. F.-E.B. - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
