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On Mon, 16 May 2005, Mark Lord wrote: > Most of us want longer lifespan and 2X the performance from our hardware, > and use UPSs to guarantee continuous power & survivability. Which is a different story and doesn't protect from dying power supply units. I have replaced several PSUs that died "in mid-flight" and that were not overloaded. UPS isn't going to help in that case. Of course you can use a redundant PSU, redundant UPS - but that's easily more than a battery-backed up cache on a decent RAID controller - since drive failure will also toast file systems. > Others want to live more dangerously on the power supply end, > but still be safe on the filesystem end -- no guarantees there, > even with "hdparm -W0" to disable the on-drive cache. As long as one can rely on the kernel scheduling writes in the proper order, no problem that I'd see. ext3 has apparently been doing this for a long time in the default options, and I have yet to see ext3 corruption (except for massive hardware failure such as b0rked non-ECC RAM or a harddisk that crashed its heads). > Pulling power from a writing drive is ALWAYS a bad idea, > and can permanently corrupt the track/cylinder that was being > written. This will toast a filesystem regardless of how careful > or proper the write flushes were done. Most drive manufacturers make more extensive guarantees about what gets NOT damaged when a write is interrupted by power loss, and are careful to turn the write current off pretty soon on power loss. None of the OEM manuals I looked at advised that data that was already on disk would be damaged beyond the block that was being written. -- Matthias Andree - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ | ||||||||||||
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