hello, thank you all for the super fast answers here, once again I have a little problem, being a novice in the field of surveillance cameras, oh yes sorry for my English I take a translator, I have 2 dahua cameras with micro sd and date everything was fine, I had notifications on my iphone and I could watch but alerts directly on my iphone, I bought a dahua nvr with a good hard drive and when it is on and switch on I still receive my notifications but I can no longer see my video on my iphone I have the impression that it records more on the micro sd, my goal was to have a backup on microsd and on the nvr at the same time, my question is how do so that the nvr records and the micro sd card also survives a configuration that I did wrong on the nvr thank you again for helping me I find your site great