#Openzfs format disk full#
Imagine the following case: You create a RAIDZ with 3 identical disks, each of them is 4 TB and you always use the full disk. One reason for not using the whole disk is that disk sizes do vary. And if it is doing well with entire disk, it would do equally well with just single partitions. If your ZFS setup is too slow, it will still be too slow if you only use entire disks.
While this statement is technically true, the speed difference is so tiny that it is entirely neglectable. People here claim that disk access is faster if you give it the whole disk. So it's not a requirement to use whole disks getting write cache advantages, it only safes you the work to enable disk write cache yourself. However, even if you just give it a single partition, nobody stops you from enabling the disk write cache yourself, in which case ZFS will detect that and honor it exactly the same was as if it had enabled the cache itself. What is true is that ZFS will try to enable the disk write cache for you if you give it the whole disk. People here claim you need to use whole disks to get disk write cache advantages, but that's not true. This will basically kill the performance, as ZFS will slice the data between the vdevs and sequential iops will turn into seek-nightmare. Don't create more partitions for ZFS per disk and if you decide to ignore the advice above, never ever build vdevs from them in same zpool. Nothing stopping you from setting it manually. With ZoL, the only difference I am aware are is that ZoL will switch the disk scheduler to noop when whole disk was given to the vdev. So once the partition is correctly aligned to the physical sector boundary, there is no reason for it to behave differently than whole block device. The overhead to translate the position on the partition to the position on the actual device is negligible. That's what Solaris automatically does, that's what FreeNAS does ( ) and that's what ZoL does when you give it a whole disk ( it will partition it). That way if you ever need to replace a drive and the replacement is 10 sectors smaller, you'll still be able to do it ( ). Use one slice/partition dedicated for ZFS per physical disc and leave some space unpartitioned.
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