Comment by poisonborz

5 days ago

Way better data security, resilience against file rotting. This goes for both HDDs or SSDs. Copy-on-write, snapshots, end to end integrity. Also easier to extend the storage for safety/drive failure (and SSDs corrupt in a more sneaky way) with pools.

19 comments

poisonborz

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wil421  5 days ago

How many of us are using single disks on our laptops? I have a NAS and use all of the above but that doesn’t help people with single drive systems. Or help me understand why I would want it on my laptop.

  • ryao  5 days ago

    My thinkpad from college uses ZFS as its rootfs. The benefits are:

      * If the hard drive / SSD corrupted blocks, the corruption would be identified.
  * Ditto blocks allow for self healing. Usually, this only applies to metadata, but if you set copies=2, you can get this on data too. It is a poor man’s RAID.
  * ARC made the desktop environment very responsive since unlike the LRU cache, ARC resists cold cache effects from transient IO workloads.
  * Transparent compression allowed me to store more on the laptop than otherwise possible.
  * Snapshots and rollback allowed me to do risky experiments and undo them as if nothing happened.
  * Backups were easy via send/receive of snapshots.
  * If the battery dies while you are doing things, you can boot without any damage to the filesystem.

    That said, I use a MacBook these days when I need to go outside. While I miss ZFS on it, I have not felt motivated to try to get a ZFS rootfs on it since the last I checked, Apple hardcoded the assumption that the rootfs is one of its own filesystems into the XNU kernel and other parts of the system.

    • rabf  5 days ago

      Not ever having to deal with partitions and instead using data sets each of which can have their own properties such as compression, size quota, encryption etc is another benefit. Also using zfsbootmenu instead of grub enables booting from different datasets or snapshots as well as mounting and fixing data sets all from the bootloader!

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  • yjftsjthsd-h  5 days ago

    If the single drive in your laptop corrupts data, you won't know. ZFS can't fix corruption without extra copies, but it's still useful to catch the problem and notify the user.

    Also snapshots are great regardless.

    • Polizeiposaune  4 days ago

      In some circumstances it can.

      Every ZFS block pointer has room for 3 disk addresses; by default, the extras are used only for redundant metadata, but they can also be used for user data.

      When you turn on ditto blocks for data (zfs set copies=2 rpool/foo), zfs can fix corruption even on single-drive systems at the cost of using double or triple the space. Note that (like compression), this only affects blocks written after the setting is in place, but (if you can pause writes to the filesystem) you can use zfs send|zfs recv to rewrite all blocks to ensure all blocks are redundant.

jeroenhd  5 days ago

The data security and rot resilience only goes for systems with ECC memory. Correct data with a faulty checksum will be treated the same as incorrect data with a correct checksum.

Windows has its own extended filesystem through Storage Spaces, with many ZFS features added as lesser used Storage Spaces options, especially when combined with ReFS.

  • _factor  5 days ago

    This has nothing to do with ZFS as a filesystem. It has integrity verification on duplicated raid configurations. If the system memory flips a bit, it will get written to disk like all filesystems. If a bit flips on a disk, however, it can be detected and repaired. Without ECC, your source of truth can corrupt, but this true of any system.

  • abrookewood  5 days ago

    Please stop repeating this, it is incorrect. ECC helps with any system, but it isn't necessary for ZFS checksums to work.

  • BSDobelix  5 days ago

    On zfs there is the ARC (adaptive read cache), on non-zfs systems this "read cache" is called buffer, both reside in memory, so ECC is equally important for both systems.

    Rot means changing bits without accessing those bits, and that's ~not possible with zfs, additionally you can enable check-summing IN the ARC (disabled by default), and with that you can say that ECC and "enterprise" quality hardware is even more important for non-ZFS systems.

    >Correct data with a faulty checksum will be treated the same as incorrect data with a correct checksum.

    There is no such thing as "correct" data, only a block with a correct checksum, if the checksum is not correct, the block is not ok.

  • mrb  5 days ago

    "data security and rot resilience only goes for systems with ECC memory."

    No. Bad HDDs/SSDs or bad SATA cables/ports cause a lot more data corruption than bad RAM. And ZFS will correct these cases even without ECC memory. It's a myth that the data healing properties of ZFS are useless without ECC memory.

    • elseless  4 days ago

      Precisely this. And don’t forget about bugs in virtualization layers/drivers — ZFS can very often save your data in those cases, too.

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