This question may or may not be specific to Apple, so let me know if I should post to Superuser or post elsewhere.
I need external storage for three purposes:
1) To make Time-Machine backups for a 1TB MacBook Pro Retina (2015 – Yosemite)
2) I also need external storage to store media
3) I will potentially install and boot / run MACOS Mojave dual and use it at the same time as the host operating system, Yosemite
It may make economic sense to use the same external storage device for all three purposes. I understand that I would need to make a separate partition for Time-Machine backups.
I assume that the external storage advertised as 1TB is not sufficient for a Time-Machine backup because its actual disk size will be <1TB and, therefore, smaller than the internal 1TB SSD of the machine ( MBPr). Based on this, you should use at least one external 2TB disk and partition 1000GB for the Time-Machine backup.
I guess I have three options, but I'm not sure which one would be the fastest and cheapest:
A) 2TB external SSD (for example, Samsung T5)
B) An internal 2TB SSD (for example, M2, Sata III, NAND or NVME? – not sure what is best here) and then converted through (connected inside) a cart (for example, Orico / Ugreen) to an external SSD with a (USB 3.0 or and Thunderbolt 2.0 connection cable / adapter?)
C) 2TB USB 3.0 Flash
I guess option B might be the cheapest one, but I'm not sure if there is any inconvenience with respect to the other easier options. I heard that there may be a problem related to TRIM, but it seems that this can be overcome through the bash script
sudo trimforce enable according to Yosemite and SSD Trim incompatibility
There is another argument that says it makes no sense to use an SSD for a time machine backup, since it would not be accessed frequently. In this case, would it make more sense to buy a cheap external HDD with 2 or more TB (this would be much cheaper than an SSD) and buy a separate SSD to boot Mojave and store media there?
Some sources say that SSD would be faster than flash, while others say that SSD these days is flash or vice versa … Does anyone have a clear idea of this (with / without a credible source)?
I guess for option B I would not use a USB 3.0 cart with a Thunderbolt adapter, since it would limit me to USB 3.0 speeds, which means that if I want to take advantage of the Thunderbolt 2.0 speeds (10 Gbps) I should use a native Thunderbolt 2.0 caddy .
I guess I can start Mojave Guest twice from an external drive with Yosemite Host on an internal drive.