I don’t immediately see the connection in your comment to what I was saying, which implies that I didn’t express my point clearly enough.
To rephrase: I interpreted FeepingCreature’s comment to suggest that 2.5 petabytes feels implausibly large, and that it to be implausible because based on introspection it doesn’t feel like one’s memory would contain that much information. My comment was meant to suggest that given that we don’t seem to ever run out of memory storage, then we should expect our memory to contain far less information than the brain’s maximum capacity, as there always seems to be more capacity to spare for new information.
I recall reading an anecdote (though don’t remember the source, ironically enough) from someone who said they had an exceptional memory, saying that such a perfect memory gets nightmarish. Everything they saw constantly reminded them of some other thing associated with it. And when they recalled a memory, they didn’t just recall the memory, but they also recalled each time in their life when they had recalled that memory, and also every time they had recalled recalling those memories, and so on.
I also have a friend whose memory isn’t quite that good, but she says that unpleasant events have an extra impact on her because the memory of them never fades or weakens. She can recall embarrassments and humiliations from decades back with an equal force and vividity as if they happened yesterday.
Those kinds of anecdotes suggest to me that the issue is not that the brain would in principle have insufficient capacity for storing everything, but that recalling everything would create too much interference and that the median human is more functional if most things are forgotten.
EDIT: Here is one case study reporting this kind of a thing: