Very slow boot: 4 - 5 minutes, due to SD-card problems !

[WiFi]

Hello,

I am a quite well experienced Raspi Fan - having started years ago - right from the early beginning of the Raspi - story.

But in the last days I have experienced a very strange problem - never seen before:

I am using an 8GB INTENSO SD-card - a supplier brand without any problems for me within years - in a Raspberry Pi 2 Model B Rev 1.1 with Raspbian GNU/Linux 8 (jessie)

Since some days I have realized that the boot sequence is taking minutes, instead estimated 60 seconds max. or less. I had assumed the root cause by special network problems when getting an IP-address via DHCP and in parallel spanning a seperate AdHoc wifi network - working with some bridge functionality.

But yesterday I have realized - the problem is very different:

Doing an SD-card image backup via win32DiskManager the Read-Process for 6GB (without unallocated blocks) took 60 minutes fairly !!!

Immediately I have assumed that the SD-card Hardware is damaged - also explaining the long boot sequence - and I have deployed a brand new 8GB intenso SD-card.
The RESTORE cycle to this with the before Backup image was done in a few minutes - so I was pretty sure, having detected the root cause for the slow boot period. Booting with the brand new SD-card confirmed me - done in 45 seconds for fully powering up - great. Heh - problem solved !

Now I did a Double Check:

I have restored the Backup also to the "broken" SD-card - you won't believe it - done in some minutes, same short Restore time as before with the new one.

Following another Check - I have now made a win32DiskManager Backup again from the "broken" SD-card - done in some few minutes (less than 5) ...! No problems any more!

I could have explained this "healing" process in a Backup & Restore cycle by some block reorganisation similar to in a fragmented file system or dammaged partition.
But we alle know, that win32DiskManager is just doing a stupid 1:1 Block copy - no intelligent structure reorganisation process behind.

What's going on here? Can somebody explain me, please?

Any ideas are appreciated, thanks for your help.

BR from WiFi

[pcmanbob]

May be your SD card had some memory blocks that were starting to fail , by doing the re-flash you may have trigged the SD cards own controller to swap these bad memory blocks out with some of the spares that SD cards have for this type of problem / failure.

Its only a guess of course and you may never actually know why or how it was fixed , one thing I would do is not use that SD card for anything important as it may fail at any time.

[LTolledo]

Not only to microSD cards
also happened on USB flash drive / SSD boot systems

as it did on mine,
experienced this on RPi3B and RPi3B+ with Raspbian Stretch Full Desktop
so I cloned the "current system" to another USB flash drive
then clone it back again to the original drive

booting time improved significantly, or should I say "went back to original speed"
...and got a system backup in the process as well.

[WiFi]

Your both answers before are reasonable for me - make sense!

Thanks very much!

BR WiFi