Re: n800, SD, SDHC, and storage
 

I'm really diggin' the two Sandisk 4GB SDHC I've got but only thing is bugging me:
The Expresscard multi-format card reader I have in my Macbook Pro won't recognize the SDHC cards but it plays just fine with all my other SD cards. I have to use a USB SDHC/SD adapter instead. Which while being fast as all get out isn't the "carry-fewer-things" style I'm looking for.
Stupid Belkin F5U213 Expresscard. No updated OS X "drivers" for it either.

Re: n800, SD, SDHC, and storage
 

Nice cheap SimpleTech "Bonzai" SDHC card reader, $13.82 from Amazon:
http://www.amazon.com/gp/product/B00...950383-7980817

Unlike the (more expensive) Sandisk MicroMate, the narrow "snout" on this device works well with the front mounted USB ports on my Antec Sonata II case, and with the crowded port layout on my trusty old Vaio Z505.

Edit: Even cheaper from Amazon's featured merchants - lowest price is currently $5.93 plus $4.99 shipping.

Re: n800, SD, SDHC, and storage
 

I came across interesting OLPC issue related to SD read speed, looks like the 12MB/s limit is not specific to N800 http://dev.laptop.org/ticket/397

Re: n800, SD, SDHC, and storage
 

Sorry to stray from the artificial benchmarks people have been batting about, but I decided to run a few symmetrical read/write tests relating to one of my own usage patterns. Specifically, I copied a 700MB set of MP3 files (equivalent to one well packed CD-R) to and from a collection of SD and SDHC cards, using both a USB-connected N800 and a SimpleTech Bonzai USB 2.0 card reader.

The host system is a homebrew Pentium D 820 (3.0 GHz) with Intel D945GNT motherboard, running XP SP2. The hard drive used for file transfers is a 10000 RPM, 74GB WD Raptor. The target cards were freshly formatted using Panasonic SDFormatter V2.0 with the default cluster size (16KB for the 1GB card, 32KB for the others) before each write test. Windows write caching was disabled, and all cards were written and ejected before the read tests were performed.

File transfers were initiated from the Windows Explorer GUI, timed with a handheld stopwatch, and reported below in minutes:seconds followed by the average transfer rate in MB/s.

Any rankings derived from this scenario are approximate, since the timings do vary across repeated runs. No attempt was made to average results over multiple tests.

Throughput becomes much lower with smaller average file sizes (such as maemo-mapper maps) and smaller cluster sizes (which store small files more efficiently). I haven't run the corresponding tests yet, but based on experience, the effect is substantial.

Presumably, memory card write performance could be improved by enabling Windows write caching on the removable volumes (Properties -> Hardware -> Policies -> Optimize for performance). However, I have not attempted to quantify this effect.

Re: n800, SD, SDHC, and storage
 

jpj:

Thanks for this comprehensive REAL WORLD speed test! :)

Based on the results the write speed seem to cap at about 2MB/sec, regardless of the card speed. In other words if buying SDHC cards going over Class 2 is waste of money. (Assuming the use is only with N800, AND future kernel updates do not enable faster transfer modes... :rolleyes: )

Re: n800, SD, SDHC, and storage
 

I guess this is because FAT table needs to be updated more often with smaller clusters (after writing each cluster if write caching is not enabled).
Yes, if one cares to use safe device removal, it makes perfect sense to enable it. Write caching may improve speed and be much more friendly to the card, updating FAT table after each block write is not ideal.

Benchmarking with write cache enabled may give more realistic write speed numbers. Even now if the final speed is 2MB/s the real write speed is much higher (double?) since for each cluster you have FAT table write = one or more additional writes (I guess two writes: block list and file size attribute).

However this http://www.uwe-sieber.de/usbstick_e.html article claims enabling write caching does not help much unless you format the card with NTFS. It is hard to believe but with Microsoft everything is possible.

Slower card may result in even slower writes i.e. if the real writing speed is 2MB/s your visible speed may be below 1MB/s because of the FAT table updates.

Of course all this is just a theory, more benchmarks could prove me wrong.

Re: n800, SD, SDHC, and storage
 

Mara, I don't entirely agree. Some genius hacker might find a way around the bottleneck. Even if they don't, and you have no other SDHC devices (today or tomorrow), a USB card reader is still a cheap speedup for getting stuff onto the card. As you can see, it helps the writes (which suffer the most) much more than the reads.

Re: n800, SD, SDHC, and storage
 

fanoush, thanks for your comments and for the article link. I intend to run some comparative tests with small files, and will also investigate the effects of cluster size and write caching. Probably not with all cards at first, as the test matrix gets pretty large. But my curiosity is piqued, so I may as well carry on...

Re: n800, SD, SDHC, and storage
 

I was thinking that if I buy some SDHC cards I may as well format them as ext2 or ext3.. I have many SD-compatible devices but none of them are SDHC compatible (with the exception of the N800+new kernel). What happens to the card reader then? Is the filesystem (FAT) known by the card reader, or is that the responsibility of the OS (say, of my linux laptop)? This has never been entirely clear to me.. I would imagine the card reader would still work but a confirmation would be nice.

Re: n800, SD, SDHC, and storage
 

TA-t3, I couldn't resist firing up my Ubuntu/maemo VMWare Appliance for a quick test. File Browser shows an entry for Generic1 Card Reader1 but is "Unable to mount the selected volume" (FAT formatted ATP 1GB SD). The error detail says "could not execute pmount."

That's all I have time for right now.

Re: n800, SD, SDHC, and storage
 

I just received my 8GB Class 4 SDHC Patriot card today and did run some quick speed test: I just copied a 327MB file from PC to the card mounted on N800, and back to PC.

The write speed was 3119kB/sec.

The read speed was 12596kB/sec.

These were taken with a stopwatch so some error margin is expected...

It looks like the Class 4 is being utilized with N800. Luckily I did not go and get the cheapest Class 2 card. :D

Re: n800, SD, SDHC, and storage
 

lol like Milhouse did.

Re: n800, SD, SDHC, and storage
 

Those read speeds are pretty similar to my Class 2 to be honest (I'd wager identical once you eliminate the variance introduced by the stopwatch timing) and the write speed I observed (6.4Mb/s) is significantly better than the Class 4 card.

All in all, I'm very happy with a cheap Class 2 device in my N800 thanks euchprof - but feel free to blow your cash on a Class 4 if you think it justified! :) I certainly don't think it is - the only benefit of Class 4 over Class 2 is when using the card in a PC card reader and performing bulk transfers where you should see improved write performance.

Re: n800, SD, SDHC, and storage
 

I didn't expect much difference in read speed, but wanted to make sure the write speed is reasonable. The Class 4 was only $5 more expensive than a Class 2 thus it was almost no brainer... :rolleyes:

Re: n800, SD, SDHC, and storage
 

In that case at $5 difference, fair enough - you can't argue with that! :)

Re: n800, SD, SDHC, and storage
 

While at it... anybody has any suggestions about PC card reader? Are all/any SDHC compatible USB card readers able to utilize Class 4 or even 6 speeds? How about bigger cards than 8GB?

In Ebay I see some but suspiciously they seem to limit up to 8GB size and talk about supporting 150X max speed and/or Class 2... :confused:

Maybe I need to search some Brand Name products and see if they publish specifications where these are defined properly...

Re: n800, SD, SDHC, and storage
 

a standard SD card reader doesnt seem to read SDHC. i got sucked into buying a 4GB SDHC card at CompUSA when i got my n800, from SanDisk and it came with a usb-2-sdhc reader. it ran $129 for the card, but the reader makes up for the ghastly price.

you can connect the n800 to a pc via usb, and read any card that is mounted in the n800.

Re: n800, SD, SDHC, and storage
 

Also, not all SD readers will read non-HC 4 GB cards. I have two that work normally in my N800, but only the built-in card reader in my pc recognizes them. A second, USB reader keeps insisting there's nothing there.

Fortunately, my cards also came with little USB readers; they're now essentially USB flashdrives with the low-capacity cards I've been accumulating over the years (well -- months...).

Re: n800, SD, SDHC, and storage
 

Replying to my own post... jpj did test multiple different cards using SimpleTech Bonzai USB 2.0 reader. In those results the Patriot 8GB Class 4 card (that I have) did get over 5MB/sec write speed, thus seem a good choice? It is also pretty cheap... :cool:

I think I'm going to get that one...

Re: n800, SD, SDHC, and storage
 

Need help, maybe i do something wrong.
I want to use with n800 Kingston 4Gb SDHC.
I'm trying to patch my n800 with sdhc kernel patch from device itself, but after string "./kernel_flasher/kernel_flash sdhc.bin" it asks "Are you ready to flash? (yes/no)" and then message appears:
"Nothing flashed.
Cleaning up... done."
After reboot n800 can't find card.
Sorry for terrible English.