08-03-2018, 08:26 AM
(08-02-2018, 02:28 PM)jovval Wrote: I have already searched the forum for RAID. If I missed something pertinent my questions, please let me know.
I do not know whether the following data are correct; regardless, I am more concerned with outliers of failure. I include these details for general information.
eMMC lifespan - https://electronics.stackexchange.com/qu...mc-is-dead - "The optimistic estimation would be based on the assumption that your system accumulates data until it can fill one complete erase block, then writes all the data in one go. In that case, your eMMC will live 4'000'000 * 3'000 / (4*20) = 150'000'000 seconds That's about 4.75 years."
microSD lifespan - https://superuser.com/questions/17350/wh...an-sd-card - "My experience with FLASH is integrity begins to falter in as little as 5 years."
1a. Can I compose a RAID1 using eMMC and microSD?
1b. How may I set the boot priority? - https://forum.armbian.com/topic/4583-rock64/ tells me how to disable, but I do not necessarily want to do so.
2. What is the performance of eMMC? (I gather that the microSD will operate at ~23MB/s, and will set the rate determining step for RAID.) The closest answer I found to my question seems to be only theoretical - https://forum.pine64.org/showthread.php?tid=4881
And, if applicable
3. How may I use /usr/local/sbin/resize_rootfs.sh on the RAID? Must I disassemble it to do one element at a time?
4. How may I use an/the store's USB adapter(s) to repeat the entire RAID1 installation (including my subsequent addition and configuration of servers)?
My question is why? if its for boot/work speed you lose a lot of speed because the system is going to wait for the slowest media to finish in writes (IIRC) (microsd in this case) or its not going to be faster than the faster media, if its for security microsd is super unreliable in any case (specially if you write to it a lot, if you are so worried about losing info im guessing its info that change a lot), a better solution is to do some automated backup externally, being a usb hdd or ssd or some cloud service...i know that this is not what you ask for but personally i wouldnt trust a microsd neither for speed nor for security not to mention that for security you also forget that both medias are inside the same device, in the case of a major tragic failure (fire, power surge) you can lose both at the same time, on the other hand if the device backup externally to a different location you can recover it...