Hi, I have an old Dell server I want to repurpose as a storage server and I decided to use zfs. I have read that gradual increases are best done with mirrored vdevs and only if I want to max out, I can choose Z2. What are your experiences in practice?
I like to go the gradual increase route because I cannot afford to maximize from the beginning. I like to start with ~10TB usable space. The server has at least 8 free drive bays. Should I go with a mirror as my first vdev or go 6x3TB with Z2? Ideally I want to be able to add more vdevs to the same pool in the future.
I am also curious whether it is a bad idea to have an uneven pool with mixed vdev types, the first being mirror and the second Z2. Will the vdevs eventually even out over time because zfs is a CoW filesystem?
@poinck Once you add a raidz vdev to a pool, you can’t remove the mirror. You’d be stuck with the mismatch until the whole pool is destroyed and rebuilt. This isn’t a technical problem, but it makes maintenance more painful (which two drive bays are the mirror, again?). If you want raidz, you should really start with it to save yourself future pain.
You also can’t increase the fault tolerance of a raidz vdev. That is, you can’t take a raidz1 and add a drive to make it a raidz2.
I personally don’t trust single-fault-tolerant vdevs. Resilvering takes long enough I want double fault tolerance for all spinning disks bigger than maybe 4 TB. That means raidz2 or three-member mirrors.