Hi,

Where and how can I check what is the transfer speed between the n800 and it's installed SD card. (I didn't buy it yet)

In case I put in the n800 a X60 speed SD card that can read and write at about 10 Mb per second (which is more than twice faster from a normal SD card), can the n800 gain from it, or the bottle neck of the data storage is on the n800 itself, so it is a waste buying a faster card?

Thanks

Hi tori, I just bought my N800 from a friend on Monday, I had my Transcend 8GB Class 6 SD card arrive yesterday. Intrigued by your post I decided to test the speed.

I managed to get a sustained write speed of 4.45MB/s to my SD card, heres how I tested it:

1) Install x-term and run these commands:

2) cd /media/mmc1
(to change the directory to where the SD card is mounted, in my case the external SD slot)

3) time dd if=/dev/zero of=deletethisfile bs=1M count=512
(what this does, is create a 512MB file, and times how long it takes to do it)

in my case, it took 1m 55s (115s). 512MB/115s = 4.45MB/s

You want to ensure that the file you create is roughly 2x the amount of ram the device has so that you know it's actually written the file to disk.

class 6 devices are supposed to be able to sustain 6MB/s IIRC, so I guess buying a faster SD card won't help.

Evan.

It may give marginally better performance, but nothing big. In any case, it is debateable whether high-speed cards are worth the expense. My class 6 card has 5.3MB/s write performance, while a not particularily specified 1GB Transcend from a bargain bin still manages about 3MB/s.

If any, it is a waste to bother with expensive "high speed" cards that lack a specified sustained rate - pre SDHC "fast" cards are often tuned towards photo applications, and can write chunks of the size of an image at the advertised rate (which often is considerably higher than the 6MB/s of the top SDHC spec), but deliver average or even worse performance (with noticeable stalls) once you exceed their internal cache size. If they stall when getting beyond their cache, you'd better not use them for the swap file, or the performance of the whole IT will get abysmal.

Sevo

With stock nokia kernel read speed tops at approx. 7MB/s, with bus speed raised to 48MHz it goes to ~11MB/s. Writes are a bit slower.

Check this http://intr.overt.org/blog/?p=54

Wow! What a difference in my cards.
External
Patriot 8GB class 4
2.46MB/s

Internal
PNY 8GB class 4
5.0MB/s

Notice that they are both Class 4 cards. So what's with the speed difference? Could it be fragmentation (on that small a card?). My internal doesn't get used nearly as much as my external, but it does have more of the space used, 80% vs. 55%.

I could be wrong, but I don't think fragmentation is really an issue on memory cards. Theres no heads to re-locate for each seek for one thing.

Correct. Fragmentation isn't an issue for memory cards. Cell access time is the same for all cells, there's no chain of sectors that have to pass by a head serially like it's for a track on a disk.

someone have tryed this kernel ?
how to flash it on my n800 ?

thanks!

Has anyone ported mdadm yet? a software stripe of the memory cards would be interesting...

Dunno why your Patriot result looks so bad... the same card (Patriot 8GB Class 4) on my N800 with OS2008 (stock kernel) on internal slot finished in 59 seconds. That makes it 8.6MB/s write speed? Somehow this seem too good to be true...

EDIT: I found the problem.. I forgot to cd to the memory card... now I got 4min 39sec, which translates just little over 1.8MB/s write speed... Not too impressive...