this is right after closing qemu-kvm

  • 3rat@lemmy.world
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    7 months ago

    What are the differences between swap a cache file? Why do you prefer the last one?

    • LordOfTheChia@lemmy.world
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      7 months ago

      Another reason for going with a swap file vs partition (if you need either) are nvme and SSD drives.

      A partition that’s only a few GB and written to constantly will wear out a solid state drive quickly.

      Using a swap file in a larger partition that has other data allows the drive to even out the wear across more storage cells.

    • Chewy@discuss.tchncs.de
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      7 months ago

      I prefer swap files over swap partitions, because it makes it my partition layout simpler to manage.

      If your using a swap partition, make sure it’s located on an encrypted partition, else it exposes data stored in RAM (encryption keys etc). With SSD’s it’s difficult to make sure this data is actually deleted, even after overwriting.

      My preferred setup for a long time was LUKS with btrfs on top. Then subvolumes for /, /home and the swap file (+ /var/cache, /var/log etc.). This gives me peace of mind nothing is unencrypted except /boot.

      Nowadays I simply use zram, which allows for a small part of RAM to be compressed for swap. It’s great, simple to setup and performs well. Imo it should be default for all desktops.

    • henfredemars@infosec.pub
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      7 months ago

      I believe there’s a language or terminology barrier and the user is really referring to a swap file versus swap partition. Swap files are much more flexible.

    • the_weez@midwest.social
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      7 months ago

      https://wiki.archlinux.org/title/swap#Swap_file

      I call them swap files but either is correct.

      A swap partition is a part of your storage disk that is formatted for swap use. It could also be it’s own disk for high performance systems, but mostly for HPC.

      A swap file is basically an empty disk image file that you mount as swap, the OS will use it just like a swap partition.

      I prefer swap files because I find them easier to manage. I can easily delete, move, or enlarge the swap file whereas the partition will take a bit more work and is a bit riskier to change. Changing partition layouts can get very messy.

      I always recommend a swap file be created when setting up a new Linux machine, even if you have loads of RAM. Some applications will use swap space to help performance, but I also like the fact that if I do something really dumb and fill up the root partition I can delete my swap file to free up space immediately, fix the full disk problem, and then recreate the swap file.

      • Luna@lemmy.catgirl.biz
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        7 months ago

        I was wondering if the extra layer of whatever filesystem the swap file is created on creates overhead? Also i think some filesystems that do COW can negatively impact performance or something? Kind of remember reading that.

        • Chewy@discuss.tchncs.de
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          7 months ago

          For swap files on btrfs COW and features like compression have to be disabled. I believe for btrfs the swap file even has to sit on a subvolume with those features disabled, so it’s not enough to only disable them for the swap file.

    • ricecake@sh.itjust.works
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      7 months ago

      So, swap is when the computer writes used memory to slow, long term storage because of memory pressure.
      Cache is when the OS sticks random bits of files into unused memory to they can be used faster.

      Using swap is a sign you need more ram. Using cache is harmless, and the OS will try to fill all free memory with cached files, because worst case scenario there’s no cost.

      • PrefersAwkward@lemmy.world
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        7 months ago

        Using swap isn’t always a sign you need more RAM. Typically, if you use a computer for a while or have a lot of IO operations going on, Linux will decide to swap some things to make more room for cache.

        Sometimes Linux just finds that you have a bunch of inactive app memory and it can swap that out to cache way more stuff. That’s just good memory management, but it’s not worth buying more RAM over