gorillagasil.blogg.se - Ubuntu logical volume manager 16.04 server

Parity information is spread across all physical devices in the vdev. These vdevs can be configured with single, double, or triple parity (and even more in recent versions of ZFS). If there are 4 disks in a mirror vdev, the capacity that you can use to store data is the capacity of the smallest disk in that structure.

Least amount of storage space available.

If there is at least one functional device in a mirror vdev, you can replace the failed drives and recover.

Fast resilvering (replacing a failed device and mirroring data back).

Slightly better than what you get with RAID-Z slightly worse than the previous non-redundant setup. This is because that is the maximum information that can be mirrored in such a setup. If you couple a 1TB disk with a 2TB disk, the usable space will be cut to 1TB. While expanding the pool with other types of vdevs is an option, it’s generally recommended you stick to the same kind of structures in each pool. Alternatively, you can create a new vdev that includes a new set of mirrored drives to expand the poll. Mirror two or more devices then later add another mirror to the same virtual device to increase redundancy.

No way to recover original data in case of read/checksum errors ZFS will report them but there’s nothing more it can do.

If one disk fails, your entire pool fails.

Easily increase pool capacity by adding more drives.

Using close to 100% of the storage space available.

If you group multiple such vdevs together, you get a structure similar to RAID-0, where data is striped dynamically across all the physical devices. You can create a vdev out of a single disk. This way a large, virtual disk can be formatted with the filesystem of your choice. The last are a kind of virtual block devices.įor example, you could combine two physical disks into a pool and then create a volume that spans on both of the physical devices. These can be: filesystems, snapshots, clones or volumes. These two vdevs make up the pool called testpool. The second vdev, mirror-1, is made up as well of two disks. Sdb and sdc are the block devices backed by whole disks.

Here’s an example of a pool: zpool status The block devices can be backed by partitions or whole disks/drives. text files).Ī ZFS pool is made up of one or more groups of virtual devices or vdevs. Compression also improves read and write speeds - sometimes considerably if the information is very compressible (e.g. Compression and deduplication can be turned on to save disk space.Clones can be created from snapshots and can be promoted to take over.You can take snapshots of your filesystems and rollback to them in case of need.

Devices can be grouped in RAID-Z arrays, similar to RAID 5, but more than three parity disks are supported.Most of the operations can be done online.This makes it possible to dynamically increase the pool size without worrying about partitioning and expanding the filesystem. A volume manager allows you to combine your physical storage devices into pools.Corrupted data will be reported and even automatically fixed if the storage pool has been setup with redundancy. Instead of “trusting” the storage device, itĬhecksums the data then stores it in separate blocks from the data itself. ZFS offers protection against silent data corruption. Since no errors have been reported by the filesystem, the backups contain the corrupted files so there is no way to recover. The drive will write incorrect data but report a successful operation. Silent data corruption can be caused by a controller fault, firmware bug, or microscopic flaw in the design of magnetic/flash memory. What is Silent Data Corruption? How Does ZFS Work?