But I never reached 30 MB / s, I do not know who to give the fault, the SD card or the Raspberry Pi or my SD card reader built into my very old PC (4 years).
In ext4 on my Raspberry Pi: average of 12-20 MB / s with peaks of 25 MB / s
Fat32 on my Windaube: 10-15 MB / s.
It has been 3 weeks that I have and I've never had a problem. I recommend this SD card, besides enjoying a very good price / quality ratio.