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> 16gb Cf For $159.99 After Rebate
boardboyd
post May 11 2007, 06:22 AM
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Found this deal while on Makezine. It is a 16Gb Sandisk Extreme CF card for $159.99 after manufacture's rebate.

16Gb 3100/3200 Anyone?
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ZDevil
post Jun 5 2007, 12:53 AM
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Off topic a bit ...
In my case I seldom had data corruption in the swapfile when I was doing quite a bit native compilation under pdaXrom. Swap partition is to prevent file corruption and wearing from spreading all over the card.
My 16gb card has two partitions: one big root (1st partition, ~15GB) and one swap (2nd, the rest of the space). Yet I am not sure if this is a good setting or not.
Now using OpenBSD on 3200, I am a bit amazed that the swap space is often not used (checking with swapctl -l), unless when running big apps with huge overhead such as firefox. Perhaps it's because of the resource-friendliness of OBSD?
For microdrive or HDD, it is advised to put the swap partition as close to the beginning to the drive as possible to improve transfer speed. But flash memory doesn't involve any spinning, so where to put the swap partition may not be an issue. I am no hardware guru at all. Please correct me if i am wrong. smile.gif
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kopsis
post Jun 5 2007, 07:57 AM
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QUOTE(ZDevil @ Jun 5 2007, 03:53 AM)
Off topic a bit ...
In my case I seldom had data corruption in the swapfile when I was doing quite a bit native compilation under pdaXrom. Swap partition is to prevent file corruption and wearing from spreading all over the card.


Partitioning may help, but the reason why is a bit more complicated. The real key to long CF life is don't ever get all the sectors on the card "used". Wear leveling needs unused sectors to work. With wear leveling, when you write to logical sector X, the card actually picks a physical sector marked as "unused", marks it "used" and writes your data there. Next time you write to logical sector X, the card picks a different physical sector, writes your new data there, then erases the previous one and marks it "unused". As a result, writes (actually its the erase before the write that wears out flash) are spread over the whole physical flash keeping any one sector from being erased and written over and over.

CF cards start with all logical sectors "unused". The first time you write to logical sector X it becomes "used". Even if you later delete the file that was using it, it is still "used" (there will forever more be a physical sector mapped to it). The CF card doesn't know anything about your filesystem. Everything is a logical sector -- and a previously written logical sector that is back on the filesystem's free list is still "in use" as far as the CF card is concerned.

Using partitions doesn't stop your writes from being spread over the physical card (nor would you want it to), but it does stop them from being spread over all the logical sectors. Without the partitioning, when the OS needs to allocate another sector, it just pulls one off the free list. That may be one that was previously "used" or it may be an "unused" one. If it's an "unused" one, you just reduced your wear leveling pool by one. Over time, unconstrained writes will cause the number of never written sectors to asymptotically approach 0. Partitioning keeps them constrained. Once every logical sector in the main partition has been written once, every subsequent allocation from the free list is forced to grab one of these previously used logical sectors and leave the logical sectors outside the partition untouched.

Good CF cards come with a decent percentage of "spare" sectors that are invisible and are always available to the card for wear leveling. Think of it as a "hidden" partition. But if you want to prolong the life of your card even more (or if you have doubts about how much protection the manufacturer has included), create a "reserved" partition with the number of sectors that you want to forever keep available for wear leveling. Do not create a filesystem in this "reserved" partition. Use the rest of the space however you see fit. Once you have some reserved space, it doesn't really matter if you use a swap file or a swap partition.

Note that you have to do this early in the life of the CF card. Once a card has been thrashed, it's not clear if there is a way to ever get the "used" sectors back to "unused". There is a low-level ATA "format sector" command that may do the trick, but it's impossible to tell if it really has any effect (and it's tough to find a disk formatting program these days that offers a "low-level format" option). That's also why buying a used CF card is such a gamble!
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speculatrix
post Jun 5 2007, 02:26 PM
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QUOTE(kopsis @ Jun 5 2007, 04:57 PM)
Partitioning may help, but the reason why is a bit more complicated. The real key to long CF life is don't ever get all the sectors on the card "used". Wear leveling needs unused sectors to work. With wear leveling, when you ...


this seemed to make sense, but I think that the logic breaks down. Lets say you have a digital camera fitted with huge 16GB CF card, and only ever write 4GB to it before "emptying". It will only take four lots before you'll have marked every sector as used?
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Posts in this topic
boardboyd   16gb Cf For $159.99 After Rebate   May 11 2007, 06:22 AM
InSearchOf   QUOTE(boardboyd @ May 11 2007, 10:22 AM)Found...   May 11 2007, 06:32 AM
ShiroiKuma   Could somebody buy this card for me, as it's o...   May 12 2007, 08:48 AM
ztep   QUOTE(ShiroiKuma @ May 12 2007, 06:48 PM)Coul...   May 15 2007, 08:16 AM
Cresho   oh MAN! I just updated to a 8gb cf card. To ...   May 12 2007, 10:05 PM
ZDevil   Great! I will be in US soon. The offer is real...   May 16 2007, 07:05 AM
ZDevil   Aaargh. The rebate form says it's for "US...   May 16 2007, 07:09 AM
Cresho   I can help anybody who wants to buy it. my email...   May 16 2007, 08:21 AM
ZDevil   Cool! Cresho, just PMed you.   May 16 2007, 08:33 AM
speculatrix   flash memory prices are dropping fast in Europe to...   May 16 2007, 10:15 AM
Cresho   sorry all! sorry, zdevil has first bids and I...   May 16 2007, 09:42 PM
ShiroiKuma   What a shame, I missed out, came second after Zdev...   May 16 2007, 09:43 PM
ZDevil   Sorry, ShiroiKuma. I guess there should be some ot...   May 17 2007, 12:01 AM
Cresho   a small update, the card works. I took a screensh...   May 21 2007, 11:35 PM
speculatrix   QUOTE(Cresho @ May 22 2007, 08:35 AM)a small ...   May 22 2007, 02:09 AM
Cresho   I did nothing to it. I just poped it in, checked ...   May 22 2007, 05:54 AM
kurochka   QUOTE(Cresho @ May 22 2007, 05:54 AM)I did no...   May 22 2007, 11:15 AM
Cresho   I just came accross a 16gb sandisk for 109 after r...   May 22 2007, 01:05 PM
ZDevil   I guess what Cresho is talking about is this one: ...   May 22 2007, 01:44 PM
ZDevil   Cool, so Cresho now has got his own 16gb card, whi...   May 23 2007, 01:16 AM
kurochka   So, what will it take to replace the internal hard...   May 25 2007, 10:46 AM
Capn_Fish   QUOTE(kurochka @ May 25 2007, 01:46 PM)So, wh...   May 25 2007, 11:24 AM
ZDevil   Finally I got the card from Cresho! Thanks...   May 29 2007, 04:30 PM
Capn_Fish   Good luck. Hope to hear reports on speed/battery l...   May 29 2007, 04:37 PM
ZDevil   I've created a slideshow of the swapping surge...   Jun 3 2007, 08:41 AM
ShiroiKuma   QUOTE(ZDevil @ Jun 3 2007, 05:41 PM)I've ...   Jul 16 2007, 10:06 PM
adf   fwiw I've been using the a-data 40x 16g for ab...   Jul 16 2007, 11:45 PM
Capn_Fish   Nice!   Jun 3 2007, 08:48 AM
speculatrix   I've seen cheap MLC cards in UK now (use froog...   Jun 3 2007, 01:25 PM
ZDevil   QUOTE(speculatrix @ Jun 3 2007, 11:25 PM)I...   Jun 3 2007, 01:40 PM
speculatrix   QUOTE(ZDevil @ Jun 3 2007, 10:40 PM)Surprised...   Jun 4 2007, 02:10 PM
adf   [there are A-Data 16 Gb cards available for @160 u...   Jun 4 2007, 04:25 PM
Capn_Fish   QUOTE(adf @ Jun 4 2007, 07:25 PM)[there are A...   Jun 4 2007, 04:32 PM
Meanie   QUOTE(Capn_Fish @ Jun 5 2007, 10:32 AM)QUOTE(...   Jun 4 2007, 05:11 PM
ZDevil   QUOTE(Meanie @ Jun 5 2007, 03:11 AM)QUOTE(Cap...   Jun 4 2007, 09:34 PM
adf   I wasn't sure about how partitioning works on ...   Jun 5 2007, 12:34 AM
ZDevil   Off topic a bit ... In my case I seldom had data c...   Jun 5 2007, 12:53 AM
kopsis   QUOTE(ZDevil @ Jun 5 2007, 03:53 AM)Off topic...   Jun 5 2007, 07:57 AM
speculatrix   QUOTE(kopsis @ Jun 5 2007, 04:57 PM)Partition...   Jun 5 2007, 02:26 PM
kopsis   QUOTE(speculatrix @ Jun 5 2007, 05:26 PM)this...   Jun 5 2007, 04:00 PM
ShiroiKuma   So concretely speaking, how does that work? If y...   Jun 6 2007, 01:16 AM
adf   and on another note entirely, I was thinking more ...   Jun 6 2007, 04:48 AM
kopsis   QUOTE(ShiroiKuma @ Jun 6 2007, 04:16 AM)If...   Jun 6 2007, 05:36 AM
ZDevil   Thanks for the precise explanation. This forum is ...   Jun 5 2007, 09:17 AM
Cresho   I just grabed this infro from the wikipedia. It t...   Jun 6 2007, 04:40 AM
wsuetholz   Not to get off topic, but does switching from the ...   Jun 28 2007, 07:12 AM
ZDevil   Okay, here is the much belated mini-benchmarking r...   Sep 19 2007, 12:30 PM


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