[s]Well, it seems that none of recoveris I found here worked on my phone. First of all, I tired to make backup on internal storage (works fine and fast) and USB-OTG (also works fine and fast).
There's a date of post where I downloaded it and the name of creator. I tried all of those recoveries. Two of them didn't show my sd card at all (0MB, twrp-220.127.116.11-peregrine-20140917-throttle and twrp-18.104.22.168-peregrine-20140818-somcom3x).
I found 5 builds and named it like this:
On one build (twrp-22.214.171.124-peregrine-20140802-somcom3x) "data" backup was OK. Then I tried to make "system" and "data" backup and it didn't worked. The same problem was with two other builds (2.8 with no throttle and 2.7 by darkshado). 2.8 with no throttle shows error that build failed. 2.7 version worked very slwoly and md5sum of system partition never ended (at least, I can't wait). I made error logs, may be it will help to developers. If it will help, I can make test and make another logs.
I tried two of my sd cards, Sandisk 16Gb and 8Gb class 10. I will try another one soon and will write the result.
I checked some things.
First of all, 16GB Sandisk is class 10 (I bought it specially for phone), Sandisk 8GB (which worked on my old LG P500 a lot of time) is UHS I.
I also tried Transcend class 6 8GB and backup was OK (on 2.8 no throttle)
And I checked files created by different version of backups and it seems that the best version that really worked and created big files was twrp-126.96.36.199-peregrine-20140802-somcom3x.img. md5 for system.img wasn't created (I think it was because of low speed, I just turned off the phone). Other 2.7 version didn't created full backup,but showed that backup was created (the progress bar (files and percent displayed normally, only 2.8 no throttle shoed that it failed to make backup and card wasn't available). But all files was less than 100MB (system.img).
Sorry for my English. Sadly that my class 10 Sandisk don't work properly. I think that they also don't work properly on stock ROM (at least on .46, didn't check .56 OTA update).[/s]
I'm sorry that I'm writing too much. Well, again, I've made some tests and saved all logs that I found. Here's the result.
1. TWRP 2.7 by somcom3x from 18 Aug and 2.8 with throttle didn't detect any sd card.
2. None of my Sandisk cards worked on 2.8 - backup failed
3. Again, Sandisk: it worked with issues on 188.8.131.52 (by darkshado from 17 Jul and by somcom3x from 2 Aug) - md5 of system generated too much time
4. Transcend class 6 worked fine on builds where SD card detected.
As I understand, this is the kernel problem. Every time it's the same issue, but results on 2.7 and 2.8 are different. I attach the logs and the file with description of results. I hope it could help developers. I'm ready to test new builds and provide log files.