[Date Prev][Date Next] [Thread Prev][Thread Next] [Date Index] [Thread Index]

Re: run debian off usb flash drive

Russell Coker <russell@coker.com.au> writes:

> On Sun, 28 Mar 2004 13:32, Goswin von Brederlow 
> <brederlo@informatik.uni-tuebingen.de> wrote:
> > > Single...what?  I suppose I wasn't clear in that this is 250 block
> > > erases for a given block.  If the erase block is 128 KiB and you have
> > > only one free block (heaven forbid) that would require writing 32 MiB
> > > of data every day for a year before that block was unable to accept
> > > another write.
> >
> > Writeing one single byte of that block is enough. Thats 250 bytes.
> Are you sure?  From a brief skim read of the JFFS2 documentation I didn't get 
> the impression that it worked like that.  JFFS2 blocks are smaller than file 
> system blocks, so 250 one-byte writes would need 250 JFFS2 blocks to be 
> written.

Hopefully the abstraction layers above the hardware gather, combine
and scatter writes so you won't get 250 one byte writes to the same
block when you write single bytes.

Point is that a one byte write still needs a 128K erase. Unless some
higher level ensures against one byte writes 250 bytes could mean 250

> Of course that just changes the problem to having only one JFFS2 block free.
> But you are right that things get worse as free space decreases.  The more 
> space you can keep free on JFFS2 the better.
> Also one thing that's noteworthy is that in what I consider to be fairly 
> typical use of an iPaQ type device, the machine is periodically refreshed to 
> the latest distribution.  This means that many files which almost never get 
> changed get put at the first blocks of the flash.  This is a minor impediment 
> to flash life.


Reply to: