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From: David Bolt on 25 Jan 2010 06:49 On Monday 25 Jan 2010 02:24, while playing with a tin of spray paint, Stephen Horne painted this mural: > On Sun, 24 Jan 2010 09:57:15 +0000, David Bolt > <blacklist-me(a)davjam.org> wrote: > >>It depends. The memory cards I have were, up until last year, used >>quite frequently in my cameras. And not wanting to lose pictures, I >>would move the images off the card as soon as possible. That sometimes >>meant emptying a card several times in a day. > > OK - so lets assume that means a maximum of 2000 writes per year to > any one block (365 days per year, averaging 5/6 erase/write cycles per > day) which seems a big much to put on one memory card (a lot of going > back to the computer to save and wipe) but what the hell. The problem is that most cards are formatted with a FAT16 file system. What this means is that every time you write to a card, not only does the memory block that stores the actual image get written, but so does a block in FAT. Well, two blocks get written in the FAT, since there's two FATs, one duplicates the other. End result is that one series of blocks will be written to with every single write cycle. And as for how often the write/read/erase cycle occurs, that all depends on the size of the card. When used in any of my cameras, and I share the same cards between three of them, taking two pictures will result in a write to two specific blocks in the FAT twice each. And then there's the directory entries. Those can move about, but writing a picture means updating the block containing those entries at least 14 times, because of the . and .. entries, and 16 times after that. Interestingly, this taught me that it's much better to read the contents off the card and then wipe it in one go, rather than to move the files off one by one. It reduces the number of writes to these blocks by close to half. It also suggests that it would actually be better to leave the pictures on the card until it is quite literally full, as this would mean the directories would be created in various places across the card, and so reduce the chances of a specific area of blocks being constantly written to. > http://en.wikipedia.org/wiki/Flash_memory#Memory_wear > > "Most commercially available flash products are guaranteed to > withstand around 100,000 write-erase-cycles, before the wear begins to > deteriorate the integrity of the storage." > > So you have "only" 50 years before you need to start worrying ;-) Except that it we already know that, with a hard drive and it's 50,000 hour, or whatever, MTBF[0], it doesn't mean that it'll be 50,000 hours before a drive fails. Some fail quickly, just being a few 10s of hours old, while others go on to exceed that 50,000 by quite some way. > To me, 100,000 cycles only seems low when thinking in terms of a main > drive - especially something like a swap partition, though you're no > doubt right to worry about last-access time stamps. A friend has an eePC. When installing Linux on it, it was recommended to not have a swap partition, and to make sure all file systems were mounted with noatime, just to minimise the number of writes to any particular block. It was also recommended to make sure that /home was mounted on a separate memory card, again to minimise the writes to the SSD. [0] While looking up the MTBF for my newest drive, I see WD have stopped using that as a way of estimating the lifetimes. Now they give a design lifetime for the components of 5 years, and an annual failure rate of 0.8%. Of course, they don't say if that 5 year lifetime has a usage of 24 hours per day, just a few minutes per day, or somewhere in-between. I'm hoping it's 24/7 since my machines are extremely rarely powered down. Regards, David Bolt -- Team Acorn: www.distributed.net OGR-NG @ ~100Mnodes RC5-72 @ ~1Mkeys/s openSUSE 11.0 32b | | | openSUSE 11.3M0 32b openSUSE 11.0 64b | openSUSE 11.1 64b | openSUSE 11.2 64b | TOS 4.02 | openSUSE 11.1 PPC | RISC OS 4.02 | RISC OS 3.11
From: JT on 25 Jan 2010 12:03 On 25/01/10 17:33, David Bolt wrote: <snipppppp> > >> Standard Linux answer: You have the code, so do it yourself. :-D >> > Hmm, I wonder why I had the feeling that you'd say something like that > :-) > Mm, can't resist that on: a) experience b) experience :) > > Regards, > David Bolt > > -- Kind regards, JT
From: David Bolt on 25 Jan 2010 12:28 On Monday 25 Jan 2010 17:03, while playing with a tin of spray paint, JT painted this mural: > On 25/01/10 17:33, David Bolt wrote: > <snipppppp> >> >>> Standard Linux answer: You have the code, so do it yourself. :-D >>> >> Hmm, I wonder why I had the feeling that you'd say something like that >> :-) >> > Mm, can't resist that on: > a) experience > b) experience And there was me thinking it was just previous experience :-) Regards, David Bolt -- Team Acorn: www.distributed.net OGR-NG @ ~100Mnodes RC5-72 @ ~1Mkeys/s openSUSE 11.0 32b | | | openSUSE 11.3M0 32b openSUSE 11.0 64b | openSUSE 11.1 64b | openSUSE 11.2 64b | TOS 4.02 | openSUSE 11.1 PPC | RISC OS 4.02 | RISC OS 3.11
From: JT on 25 Jan 2010 12:46 On 25/01/10 18:28, David Bolt wrote: > On Monday 25 Jan 2010 17:03, while playing with a tin of spray paint, > JT painted this mural: > > >> On 25/01/10 17:33, David Bolt wrote: >> <snipppppp> >> >>> >>>> Standard Linux answer: You have the code, so do it yourself. :-D >>>> >>>> >>> Hmm, I wonder why I had the feeling that you'd say something like that >>> :-) >>> >>> >> Mm, can't resist that on: >> a) experience >> b) experience >> > And there was me thinking it was just previous experience :-) > > > Regards, > David Bolt > > I knew I forgot to mention one. That _and_ new experiences of course. So that 'll make 4 then? -- Kind regards, JT
From: script||die on 25 Jan 2010 13:42
On 01/24/2010 03:30 PM, houghi wrote: > script||die wrote: >>> http://www.flickr.com/photos/19428171(a)N00/2446994680/ >>> http://www.flickr.com/photos/19428171(a)N00/2446992282/ >> >> Why oh why would a body spend 1500 just to place a FF fox icon where the >> only morally acceptable one is the old netscape one? > > I have no idea. Perhaps to make it clear that that button starts > firefox and not Netscape? > > I could see some use for this kind of keyboard. If you run Emacs, you > could program it to show what kind of things you can do. But as Emacs s > evil, who really cares. > > houghi Evil? Like earthquakes or just "I hit return yet it wouldn't kiss me"? |