Re: Tuning for Compact Flash

[Christer Weinigel <christer@weinigel.se>]

jim owens wrote:
> Christer Weinigel wrote:
>> I installed Fedora 9 on the Compact Flash, with a small boot partition 
>> and then one large encrypted LVM partition where I put the swap 
>> partition and an ext3 file system.  This turned out to be bog slow, 
>> write speed to the ext3 file system seem to be about 1MByte/s which is 
>> just horrible.  Since Transcend claims 45MByte/s read bandwidth and 
>> 16MByte/s write bandwidth, this seems much too low.
> 
> CF is not an SSD.  A CF is designed and spec'd to store large images.
> Neither CF nor USB thumb drives are intended as a primary system
> hard drive.  They work great for transferring data between machines
> but no filesystem or tuning will make them perform with the same
> characteristics you expect of your primary hard drive.

Of course it won't behave like a hard drive, but it would be nice if 
there was a file system with performance that didn't suck as badly on a 
compact flash.  Plain NAND flash is nothing like a hard drive either, 
but with a file system designed for the peculiarities of NAND flash, it 
does behave decently.

And it seems that the Silicon Motion SM223 controller used for Transcend 
Compact flash is the same that is used in some models of the Asus EEE 
and in a Transcend SSD, so in this case a CF is a SSD.

Anyway, I think I'll write a couple of more test programs to explore the 
performance characteristics of my particular flash device, see how 
alignment and accesses to different areas on the flash behave (since 
Artem mentioned that they may be optimised for FAT).

But I was hoping that someone else had already done this.  I can't be 
the only person with a laptop where a SSD won't fit and who wants to run 
Linux off a common of the shelf flash disk.

   /Christer