SFS Filesystem and CF cards, wise choice?

Ed.D

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Just been reading about SFS on Wiki (can't sleep :coffee:).

Apparently SFS has built in self defragmentaton. I am wondering if this is a good filesystem to use with a CF card given the finite number of writes these card apparently have, or is self defragging a configuable parameter?

Any thoughts anyone?
 
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Rixa

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My gut feeling is that fragmentation doesn't matter that much at all with a flash memory device, since it doesn't have a physical head that needs to move back and forth to get all the bits from here and there. If that is right, defragmentation doesn't help and can only hurt.

I'm not sure how quickly those devices wear out, it depends on whom you ask. If you ask the card manufacturers they basically tell you how many millions of times they can be written deduce that that even with heavy use they're right on par with hard disks. A couple of years ago I was being advertised some blade server cards, and noticing that they had a CF slot on board I asked the tech what it's good for. His opinion was that it should be used only for storing mainly static configuration data and not as the system disk, because it would be broken in no time. He was of the opinion that those cards are being made for cameras, people just fill them a couple of times and end up losing them or getting new ones before they break.

The truth is probably somewhere in between.
 

rkauer

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SFS is good as any other file system, like PFS2 or 3. I still prefer the old and reliable FFS for my Amiga partitions on flash media.

SFS, PFS and AFS are faster, but they have the horrible habit of messing up the partition when you less wait for it. And they don't have tools to recover the data when it happens.
 

Tomse

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I once asked a professional photographer about the usage of her flash memory and she told me that they replaced them every year or so..

this was a newspaper photographer..

now the flash technology has gotten better and they don't wear as much as before (some say they can last infinitiv).

but like with anything else, I'd recommend you to take a backup of your drive every now and then as minimum.
 
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Rixa

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I also use FFS on my Amiga internal CF card. It is a very good point that since it has been common it is well supported by recovery tools and whatever. I don't know how reliable it is, but my experience has been good. I'm using FastFileSystem 45.13 from OS3.9 BB2 with an unofficial patch for a memory leak from Aminet.

In theory a journaling filesystem should be more reliable in some situations, for example a poweroff during a write; you would still lose the file but the filesystem should remain unbroken. In practise, I don't know - it also means increased complexity which brings more places where something can go wrong. All software has bugs. Journaling is also doing more writes, which is of issue here.

There are other considerations that affect those writes. Does the filesystem keep a 'last accessed' time for each file, like POSIX-compliant file systems do? This means every time you read a file, you also write a block. Is the filesystem metadata kept in the same place on the disk at all times? Every time the filesystem contents change, this spot is getting more and more worn and when it finally does break your entire filesystem is in big trouble. What about when you repeatedly edit a file, will it overwrite the same blocks every time? There's probably more, that's just all I can think of off the top of my head. I don't know the answers to these questions either, even for FFS.

The flash cards are doing some hardware level wear leveling themselves, but I don't know if how exactly they do this is public information. Seeing that they are usually intended to carry a VFAT file system that does no wear leveling itself, it is probably doing something or they would break much sooner.
 

Zetr0

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SFS has quite a few tools to help repair any damage done by a failure in the OS/FileSystem

I have had a very good success rate with SFS - when compared to FFS (even the patched one).

I will note that there some instances with FFS (patched version) where the supposed tool have broken the FileSystem further. (either there not 64 bit complient or a combination of a bad disk) - however with SFS there was no problems at all.


Now, to turn this on its head, I have a CF card here (64MB) that WONT take an SFS format on it... on FFS - freaky eh?


For me the only draw-back is that SFS can only be used on an 020 cpu or higher - I long for the release of PFS2/3 to the community - thus I can finally get a 20GB HDD on my A500+
 

wurzel

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SFS is good as any other file system, like PFS2 or 3. I still prefer the old and reliable FFS for my Amiga partitions on flash media.

SFS, PFS and AFS are faster, but they have the horrible habit of messing up the partition when you less wait for it. And they don't have tools to recover the data when it happens.

I can`t comment much about this, except to say that PFS3 does have tools to recover lost data. I`ve only needed them when I do something wrong - PFS3 has been very reliable for me.

I especially like the fact you can recover up to 1000 "deleted" files - many`s the time I deleted somthing by accident, but was able to recover it in a few mouse clicks ;)
 

rkauer

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PFS3 is now freeware, I think I posted that before. A public keyfile will be released soon, probably on Aminet.

But surely on Amiga.org
 
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