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I have an external SSD 1 TB plugged in to Linux-Laptop. I have created a small new partition - 10 GB size on it, so now I have 2 partitions on that SSD. Both partitions are formatted with ext4 file system.

I download a lots of videos from youtube on that small 10-GB-partition every day.

If a bad sector/bad block appears on the small 10-GB-partition will it affect the other partition so that the files on it will be corrupted/broken/unreadable/lost?

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  • AFAIK, no. SSDs, like HDDs, have spares they'll swap in that aren't assigned to any partition, with the bad block being marked as so and not used again. Depending on the size of the videos and how many accumulate on the 10GB partition, the small partition size may result in rewriting blocks unnecessarily if there's not enough free space to move data around on the partition from the firmware's point of view (there are writeups that explain why this is)
    – JW0914
    Commented Jun 16 at 11:49

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No. Any bad sectors/cells affects only data stored in that sectors/cells. With multiple bad sectors on drive/partition your OS could starting complain about damaged filesystem. However it complaints mostly for filesystem on which bad sectors are stored.

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The partitions are just a thing from our perspective, at the logical block level. The physical blocks assigned to a partition, take for example the 10GB partition, change over and over as you keep saving data to it.

The partitions are red herrings in this question, sort of. Due to how SSDs handle memory, the LBA layer is separate from the physical layer and their connection is a dynamic mapping table (FTL).

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If the drive would run into a bad block and it decided to reallocate it, it has no effect on any particular partition other than data in the block could be lost (and thus the partition the block is correctly assigned to), but does on the overall drive's health. After all, after eventually the drive 'runs out' of spares, the drive may declare it's unsafe to continue using the drive.

Some notes ..

  • An underlying cause for the bad sectors could affect the whole drive and other partitions, for example degrading NAND.
  • One LBA block is only a subset of a 'physical block', (LBA block = subset of Page = subset of Erase Block). SSD can write per page, but can only erase per erase block.
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  • Some more considerations though: a "physical block" could be bad without the controller being aware of the fact and got unmapped from logical block(s) belong to one partition and mapped to some other that belong to another; also a "physical block" (whatever that refers to in terms of SSD; just not the "PB" in the reported "PBS") is always larger than a logical block, meaning that one could be mapped to multiple logical blocks that belong to different partitions.
    – Tom Yan
    Commented Jun 16 at 19:31
  • @TomYan - Yes, physical block could be bad without controller being aware. It's always a good idea to run some surface scan to make it aware. If it was unmapped due to for example TRIM it will find out when it starts actually erasing the block. Yes, true, LBA block is subset of a physical block / erase block. Thank you, I'll see how to add that.
    – Joep van Steen
    Commented Jun 16 at 19:36

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