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more info about zpool and vdevs

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eater 2020-10-23 18:40:02 +02:00
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data/posts/pre-flight-nas-checklist.md
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@ -94,9 +94,10 @@ First there's ARC, ARC will eat your memory, worse than a webbrowser does, BUT i
Then there's how ZFS internally works, if you're planning to expand over time, this is _very_ important.
ZFS works with `zpool`'s and `vdev`'s.
A `zpool` is basically the mount or disk™ you'll be seeing inside your OS, while a `vdev` is a set of disks in a particular RAID setup.
Now this is an important distinction because a `vdev` is immutable (except for replacing disks), this means you're unable to remove (yes, removing a disk is Very Hard resulting in me calling `zfs` a poison) or add disks to a vdev.
A `zpool` is basically the mount or disk™ you'll be seeing inside your OS and is basically a bunch of `vdev`'s together (kind of a bunch of `vdev`'s in RAID0), while a `vdev` is a set of disks in a particular RAID setup, acting as a single (virtual, yes that's where the `v` comes from) device.
Now this is an important distinction because a `vdev` is immutable (except for replacing disks), this means you're unable to remove (yes, removing a disk is Very Hard resulting in me calling `zfs` a poison) or add disks to a `vdev`.
So if you chose ZFS, be aware that you need to add disks in pairs, this means if you're using RAID1/mirror, you need to add 2 disks at a time, if you're using RAIDZ you need to add 3 disks at a time etc.
Everytime you add a new pair of disks to your pool, you'll be adding a new `vdev` in that RAID setup, you can also technically mix and match, but uhh. I don't recommend that.
If you're just throwing a portion of your income to your NAS this can be very frustrating since you might need to wait for a few months to add new storage, while you have the disks laying around for a while.