Mick <michaelkintz...@gmail.com> [15-08-07 20:04]: > On Friday 07 Aug 2015 04:27:15 Fernando Rodriguez wrote: > > On Thursday, August 06, 2015 6:18:59 PM meino.cra...@gmx.de wrote: > > > Hi, > > > > > > for my tablet PC I used a used 32GB FAT32 formatted SDcard. The > > > formatting was already done by the manufacturer. > > > Then I screwed it up and had to do the partioning and formatting > > > myself again. "No big deal", I thought -- and was wrong. > > > Yes, the "thing" I got could be read and written. But it was > > > DAMN slow in comparison to the original formatting. > > > > > > I googled and found a description, which described exactly, > > > what I wanted: An optimal formatting for one big FAT32 partion. > > > I did it again ;) and: TADA! The speed was back. > > > LINK:http://zero1-st.blogspot.de/2012/05/formatting-fat32-volumes-larger-> > > > > than.html > > > > > > Now I need the something identical but explained in a way > > > that it can be successfully applied to any partion layout > > > and any SDcard size. > > > Currently the new SDcard has 64GB (yes, the tablet eats that size > > > well :) and needs at least two partions: One FAT32 and one ext4. > > > May be that I need a different layout later. > > > > > > To what aspect and "logic" do I have to keep my eyes on, when > > > it comes partioning/formatting any SDcard size with any partion > > > layout and any filesystem? > > > > > > Thank you very much in advance for any help! > > > Best regards, > > > Meino > > > > I wrote a long reply to this and it appears to have been swallowed by > > /dev/null. > > > > SD cards don't have 128K blocks. Except for the very early ones (standard > > capacity), they are divided in allocation units (AU) that are 1MB to 4MB > > for SDHC and even larger for SDXC. The only way to get that value is by > > reading a register in the card (so you can't do it in usermode on linux). > > > > The AUs are divided into Recording Units (RUs). The size of these can be > > deduced from the card speed class (that's the number inside the C on the > > label), and the card capacity. For class 2 and 4 if the card is less than > > 1GB it's 16KB, otherwise it's 32KB. For class 6 it is 64KB, and for class > > 10 it's 512KB. > > > > After an AU is erased you can write to any of the free RUs in any order in > > blocks of 512 bytes sequentially (the block size is configurable by the > > driver but 512 is the most common). But if you write to a nonfree RU then > > all non- free RU get copied to a new AU. So the performance hit depends on > > how many non-free RUs are in the AU when this happens. > > > > So to get the best performance you need to align the first FAT cluster on > > an AU boundary and that the RUs used by the reserved sectors after the FAT > > are free. This is not so easy from usermode because you can't get the AU > > size and you can't erase the AU to make sure reserved sectors are free. > > The Windows 7 and later format utility will do it if you don't partition > > the card. The next best thing is to align it to an RU which should be > > pretty easy. > > > > You could guess the AU size by writting blocks of RU size from the start of > > the card and timing it. Every time you hit the AU boundary there will be a > > longer delay. > > > > For more details see the SD specification (chapter 4.13). > > > > https://www.sdcard.org/downloads/pls/ > > > > They also have formatter tools for Windows and OSX. I tried the Windows > > version years ago but had problems with it (can't remember what). > > Excellent information Fernando, thank you! > > So there is no tool for me to use to read the AU/RU on the chip? > > -- > Regards, > Mick
Hi, sorry for being a little late...was too busy and my sdcard is still not formatted... ;) Thank you very much for the help and all the informations. Currently I start to understand the problems and solutions in formatting ONE partition with a FAT32 filesystem on a sdcard the correct way, but when it comes to more the one partition and filesystems for example like ext4fs I still dont know how to... Just a few minutes before I found this: http://www.bradfordembedded.com/2014/05/flashbenching/ http://wiki.laptop.org/go/How_to_Damage_a_FLASH_Storage_Device https://github.com/bradfa/flashbench http://wiki.laptop.org/go/SDCard_Testing https://lists.linaro.org/pipermail/flashbench-results/ https://blogofterje.wordpress.com/2012/01/14/optimizing-fs-on-sd-card/ I am still in the process of reading and hopefully understanding this... Best regards, Meino
