Messages in this thread | | | Date | Mon, 13 Oct 2008 14:38:34 -0400 | From | Chris Snook <> | Subject | Re: Filesystem for block devices using flash storage? |
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Jörn Engel wrote: > On Mon, 13 October 2008 13:30:29 -0400, Chris Snook wrote: >>>> logfs tries to solve the write amplification problem by forcing all write >>>> activity to be sequential. I'm not sure how mature it is. >>> Still under development. What exactly do you mean by the write >>> amplification problem? >> Write amplification is where a 512 byte write turns into a 128k write, >> due to erase block size. > > Ah, yes. Current logfs still triggers that a bit too often. I'm > currently working on the format changes to avoid the amplification as > much as possible. > > Another nasty side effect of this is that heuristics for wear leveling > are always imprecise. And wear leveling is still required for most > devices. See http://www.linuxconf.eu/2007/papers/Engel.pdf > >> Intel is claiming a write amplification factor of 1.1. Either they're >> using very small erase blocks, or doing something very smart in the >> controller. > > With very small erase blocks the facter should be either 1 or 2, not > 1.1. Most likely they work very much like logfs does, essentially doing > the whole log-structured thing internally. > > Jörn >
As I understand it, they mean that in a real-world workload that writes 1x data, a total of 1.1x is written on flash. Real-world writes are usually, but not always, larger than a single sector. Of course, the validity of this number depends greatly on the test.
If someone has more info on the Intel devices, please clue me in.
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