Messages in this thread | | | Date | Thu, 17 Jun 2004 23:18:56 -0700 | From | Hans Reiser <> | Subject | Re: mode data=journal in ext3. Is it safe to use? |
| |
Ken Ryan wrote:
> Hans Reiser wrote: > >> Timothy Miller wrote: >> >>> Doesn't Reiser4 do wear-leveling for flash? >> >> >> >> No, we don't. We do have wandering logs, so it would be feasible to >> code, but bitmap blocks and super blocks get written to the same >> locations repeatedly. >> >> Actually, most compact flash devices DO do wear leveling, from what I >> have heard. > > > > The ones I've seen, only sort of. They'll allocate writes from > available erased pages to try to distribute their use, but if you > have a disk that's, say, 70% read-only data and 30% read-write then > the wear-levelling will only happen on that > 30% of the disk. True wear levelling will actually scrub read-only or > rarely-written data, forcing it to get off its > duff so the flash cells they're sitting on can get some exercise, and > give the more worn cells a rest (that scrub > helps ECC fix soft errors from weak cells too). True wear-levelling > is really hard, and obviously requires > budgeting extra bandwidth and storage devices for safely shuffling > around data that the application has no > intention of moving (picture losing power in the middle of a scrub). > It's not worth it for the consumer CF > usage model of "take photos until the card is full, then copy them all > to the PC and wipe the card clean". > > [Yes, I tend to see this from the inside-out: I'm actually an > FPGA/ASIC weenie not a kernel hacker. One of my current > projects is part of a controller chip for a solid-state storage system > with ${bignum} NAND flash chips. Alas, my specialty > is video and graphics, so I'm still coming up the learning curve on > storage systems]. > > ken > > > > > Interesting. Thanks for educating me.
No existing general purpose filesystem that I know of will address your needs. We could of course write one if someone paid for it.... - 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/
| |