3 ms·

Also, by not duplicating, you presumably increase probability of data loss considerably. Now you lose data if either of the devices (SSD, HDD) fails. That certa

• simonh 14y ago
  But in a cache, if the main storage fails you can't just get the data off the cache anyway. On it's own it's not a filesystem the OS can read, as it's managed by the device driver. In theory the data is there, but there'd be no practical way to get at it. In a fusion drive, if one drive fails it looks like you'll still be able to recover the data on the other drive.
  • gmac 14y ago
    OK, but the probability of data loss is still worse than with a cache, because failure of (HDD or SSD) is likelier than failure of HDD alone.
    • simonh 14y ago
      But a HDD with a flash cache is still a hdd component and a flash component. Putting them in the same enclosure and using one of them as a cache for the other doesn't magically merge their combined MTBFs into a lower number.
      • mistercow 14y ago
        That is correct. While gmac is technically correct that you have a higher expected amount of data lost with the non-caching system than you would with the caching system, but that's just the trivial fact that more space = higher loss expectation.
• mistercow 14y ago
  To be fair, if either of those fails on an HHD, you're almost certainly going to lose some data anyway (whatever hasn't been written back to the HHD yet). And I would expect the HDD to fail long before the SSD anyway, which is going to cause you to lose almost everything.