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linux:fs:zfs:draid [2023/02/08 10:47] – created niziaklinux:fs:zfs:draid [2025/08/03 07:39] (current) – niziak
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-====== draid ======+====== dRAID ====== 
 +declustered RAID 
 + 
 + 
 +From [[https://pve.proxmox.com/wiki/ZFS_on_Linux#sysadmin_zfs_raid_considerations|ZFS RAID Level Considerations]] 
 +<code> 
 + 
 +In a ZFS dRAID (declustered RAID) the hot spare drive(s) participate in the RAID. Their spare capacity is reserved and used for  
 +rebuilding when one drive fails. This provides, depending on the configuration, faster rebuilding compared to a RAIDZ in  
 +case of drive failure. More information can be found in the official OpenZFS documentation. [1] 
 +Note: dRAID is intended for more than 10-15 disks in a dRAID. A RAIDZ setup should be better for a lower amount of disks in most use cases. 
 +Note: The GUI requires one more disk than the minimum (i.e. dRAID1 needs 3). It expects that a spare disk is added as well. 
 + 
 +    dRAID1 or dRAID: requires at least 2 disks, one can fail before data is lost 
 + 
 +    dRAID2: requires at least 3 disks, two can fail before data is lost 
 + 
 +    dRAID3: requires at least 4 disks, three can fail before data is lost 
 +</code> 
 + 
 +From [[https://openzfs.github.io/openzfs-docs/Basic%20Concepts/dRAID%20Howto.html|dRAID Introduction]] 
 + 
 +<code> 
 +dRAID is a variant of raidz that provides integrated distributed hot spares which allows for  
 +faster resilvering while retaining the benefits of raidz. A dRAID vdev is constructed from multiple  
 +internal raidz groups, each with D data devices and P parity devices. These groups are distributed  
 +over all of the children in order to fully utilize the available disk performance. This is known as  
 +parity declustering and it has been an active area of research. The image below is simplified, but  
 +it helps illustrate this key difference between dRAID and raidz. 
 +</code> 
 + 
 + 
 +<code> 
 +We especially caution storage newbies to be careful with draid—it's a significantly more complex 
 +layout than a pool with traditional vdevs. The fast resilvering is fantastic—but draid takes a hit in 
 +both compression levels and some performance scenarios due to its necessarily fixed-length stripes. 
 +</code> 
 + 
 +<code> 
 +draid2:2d:14c:1s 
 +     |  |  |  | 
 +     |  |  |  L-> one spare 
 +     |  |  | 
 +     |  |  L-> total number of disks to use 
 +     |  | 
 +     |  L-> number of data disks per disk group 
 +     | 
 +     L-> number of parity disks per disk group 
 +</code> 
 + 
 +===== Usage ===== 
 + 
  
 Create DRAID with 1 parity and 2 redundancy (on 3 disks): Create DRAID with 1 parity and 2 redundancy (on 3 disks):
 +
 +<code bash>
 +zpool create backup draid1:2d:3c <disk1> <disk2> <disk3>
 +</code>
 +
 +Create DRAID with 1 parity and default redundancy (on 5 disks):
 +
 <code bash> <code bash>
-zpool create backup draid1:2d <disk1> <disk2> <disk3>+zpool create backup draid1:5c <disk1>..<disk5>
 </code> </code>