[mythtv-users] boot off compact flash

Tim Small tim at buttersideup.com
Sat Apr 21 19:39:11 UTC 2007


Mitch Gore wrote:
> I want to build a ultra quiet front end.  I was thinking about using a 
> LiveUSB version of linux but than I ran across this device.
>
> http://www.newegg.com/Product/Product.asp?item=N82E16822998003
>
> From what I understand it just plugs into the IDE port and then you 
> connect a CF disk.  Has anyone ever tried this?  If so how is the 
> speed compared to a regular IDE drive?
I've used these plenty of times, and have been happy with the 
performance.  Being flash, random access performance is good, but 
sequential is poor, similarly, reads are a lot faster than writes.

They can be got on ebay even cheaper, I think (also in other 
formfactors, e.g. 2.5" 44pin IDE connectors, and ).  The adaptor is 
pretty simple, as CF cards impersonate IDE drives as one of their 
personalities (they also do PCMCIA, and some do USB natively as well).  
CF cards theoretically implement wear-levelling, but there are anecdotal 
reports of at least some not actually implementing this.  There is a lot 
of performance variation between different models of CF card (e.g. some 
support newer EIDE transfer modes, such as UDMA).

As you have no access to the native flash layout (unlike SD cards, I 
think), you can't use any of Linux's flash-aware filesystems.  Some 
people have reported wear-out (but I've never seen this myself), and as 
a result, you might want to consider a non-journalling filesystem, such 
as ext2. 

Same problems apply for USB sticks, I should think....

Native flash (with native flash file systems) are a much better idea, 
but more difficult to implement (at least on x86).

Tim.


p.s. Years ago, I did have one CF card die when there was a 
power-failure during writes.  I got it back with an IDE low-level 
format, but the data was lost...


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