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> If sda was already mirrored with sdb, you now have a triple-mirror with sda, sdb, and sdc. You probably already know this, but btrfs offers a different optio
by wtallis 5y ago
> If sda was already mirrored with sdb, you now have a triple-mirror with sda, sdb, and sdc.
You probably already know this, but btrfs offers a different option. Its "RAID1" mode would not result in the three drives storing your data in triplicate but rather still stores data in duplicate but with a usable capacity that's 1.5x that of a single driver's capacity. To get the ZFS behavior you describe, btrfs offers a "RAID1c3" mode, but that's a much less interesting feature.
- NavinF 5y agoHuh I didn’t know that. Seems like a niche feature, but it’s still pretty neat!
- rodgerd 5y agoIt's a neat feature for SOHO-type users, and takes advantage of the fact that the RAID layer knows about the FS. The first implementation that I know of is Drobo's filesystem. Asymmetric RAID is probably the only config that I'd like to see in ZFS - being able to have (say) an 8TB drive and two 4TB drives, and have 8TB of mirrored space is quite nice when you're just buying commodity kit and don't want to have to retire/match drives all the time when growing mirrors.
- wtallis 5y agoYep, SOHO use cases are where this kind of capability is really useful. ZFS is great when you buy drives by the dozen, but even with this feature it's still inconveniently inflexible if you only have the budget to be upgrading or expanding one drive at a time.
- mgerdts 5y agoSounds like the way that Windows Storage Spaces works as well.