CF cards as storage - wear leveling

[Jon Elson]

On 03/19/2017 11:06 AM, Jules Richardson via cctalk wrote:
>
> I just bought an IDE-CF adapter the other day with the 
> intention of replacing the spinning rust in my disk 
> imaging system (which is some early/mid-90s 80486-based 
> thing).
>
> However, the CF entry on Wikipedia says:
>
> "Most CompactFlash flash-memory devices limit wear on 
> blocks by varying the physical location to which a block 
> is written. When using CompactFlash in ATA mode to take 
> the place of the hard disk drive, wear leveling becomes 
> critical because low-numbered blocks contain tables whose 
> contents change frequently. Current CompactFlash cards 
> spread the wear-leveling across the entire drive. The more 
> advanced CompactFlash cards will move data that rarely 
> changes to ensure all blocks wear evenly."
>
> ... I'm a little wary about the way it says "most CF 
> cards", implying that there are some out there which don't 
> do any wear-leveling at all. So, the obvious question: is 
> there a way of knowing which cards are going to be good 
> and which are useless as IDE replacements? Maybe by age, 
> capacity, manufacturer? I'd prefer not to invest time into 
> setting software up only to find that the card fails in a 
> matter of weeks.
>
I have several systems that have the old Beagle Board 
computer in them.  They are not run continuously, but have 
been run for months at a time.  These use regular-size SD 
cards as the "disk" for a Linux OS.  I did set the noatime 
flag on the file system.  They are still running on the 
original SD cards.

I have a Beagle Bone running LinuxCNC under a Debian-based 
distro, and I fire it up at various times to text boards I 
make, and it is still running the original micro-SD card.

I don't think anybody is actually using real CF cards 
anymore, they are about a decade out of date.

Jon