Messages in this thread | | | Date | Tue, 01 Apr 2008 12:57:46 +0300 | From | Artem Bityutskiy <> | Subject | Re: UBIFS vs Logfs (was [RFC PATCH] UBIFS - new flash file system) |
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Tomasz Chmielewski wrote: > Such as?
ext3 for example.
> Flash (also on block devices) is slow and expensive (when compared to > modern hard disks) and therefore compression is *very* useful here. Well, if you are ready to trade performance to compression, then well, go ahead :-) May be I used too strong wording, but I wanted to say then use raw flash then. But I'd also consider implementing compression support for a block based FS. Reiser4 claimed to have it for example.
> Do you mean using hacks like block2mtd? It's hacky, and pretty hard to > boot a system this way (need to build own initramfs, with a static > block2mtd or loads of libraries - not something an average user would > like to do; no distro supports it; updating a kernel would be a pain etc.). Well, ok, it still sounds strange for me, but you may use JFFS2 and UBIFS with block2mtd as well if you really want to.
> True. > Unfortunately, there is no way to access flash directly on flash-based > block devices (USB-sticks, IDE-flash disks, SSD disks etc.). Yeah, that's a pity :-(
> Unfortunately, traditional filesystems were rather designed for rotating > media / cheap disks (no transparent compression; tend to accumulate > writes in one area of the disk - more on that - below). Sure.
> Performance is only one factor in the equation. Other factors are: cost > and reliability. > > I speak from experience: flash-based block devices tend to have poor > wear-levelling (at least Transcend IDE-flash disks). > To reproduce: > - format a 2 GB Transcend IDE-flash disk with ext3 > - write a small file (50-100 kB) > - update that file ~several hundred thousand times - as you finish, > IDE-flash disk will have 200-300 badblocks Yeah, that's bad. But if you have a bad FTL, surely there is not guarantee a flash FS will help? Isn't it better to use better hardware?
We did some experiments with MMC cards and we were unable to wear them out with re-writing the same sectors again and again. This suggests there _is_ better FTL hardware then that USB stick you was using.
Anyway, your original mail said Logfs can work with block devices. My answer - UBIFS too, but this is very strange to do this IMO. But OK, it might is not senseless, sorry for the wording. :-)
-- Best Regards, Artem Bityutskiy (Артём Битюцкий) -- 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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