Enterprise Deployment

ZFS is commonly deployed in enterprise environments due to its scalability and advanced features for managing data. When deploying ZFS in production, particularly in enterprise contexts, two important considerations are high availability (HA) configurations and the use of ZFS in virtualized environments like VMware and KVM.

High Availability Configurations

High availability (HA) ensures that services remain operational during hardware or software failures, minimizing downtime. In ZFS, high availability is achieved through clustering, redundancy, and automatic failover setups.

Clustered ZFS Storage with Failover

A common approach to achieving HA with ZFS is through a cluster setup. Multiple nodes are connected to shared storage, and one node is active at a time. In case of a failure, another node can take over the storage pool and continue serving data.

ZFS pools are placed on shared storage accessible by multiple nodes, often using iSCSI, Fibre Channel, or a NAS over NFS. The nodes access the same storage, but only one node actively mounts and serves the pool at a time.

Cluster management tools such as Pacemaker and Corosync detect node failures and automatically switch the pool and services (such as NFS or SMB) to the backup node. Pacemaker triggers failover when the active node becomes unavailable, allowing the backup node to take over with minimal downtime. Nodes communicate via Corosync to detect failures.

Here’s a basic example of configuring ZFS clustering with Pacemaker:

# Configure ZFS resource for Pacemaker
$ sudo pcs resource create zfspool ocf:heartbeat:ZFS pool=myzpool
$ sudo pcs resource group add zfs_group zfspool

For remote failover, ZFS replication keeps the backup node in sync with the active node. Periodic replication can be set up using zfs send and zfs receive:

# Incremental replication
$ sudo zfs send -i mypool@prevsnap mypool@currsnap | ssh backup_node sudo zfs receive remotepool

Here’s an ASCII diagram illustrating a simple two-node HA cluster:

+---------------+         +---------------+
|     Node 1    |         |     Node 2    |
|  Active ZFS   |         |  Standby ZFS  |
+---------------+         +---------------+
      |                          |
      |  Pacemaker + Corosync    |
      +--------------------------+
           | Shared Storage |
           +----------------+
                [myzpool]

Mirroring and RAID-Z for Redundancy

For smaller deployments that do not use clustered setups, ZFS’s built-in redundancy features provide high availability through mirroring or RAID-Z configurations.

In a mirrored configuration, data is written to multiple disks simultaneously. If one disk fails, the system continues to operate using the remaining disk(s). The mirrored pool can be created with the following command:

# Create a mirrored pool
$ sudo zpool create mypool mirror /dev/sda /dev/sdb

RAID-Z1, RAID-Z2, and RAID-Z3 configurations provide redundancy by distributing parity across disks. For example, RAID-Z2 allows two disks to fail without data loss:

# Create a RAID-Z2 pool
$ sudo zpool create mypool raidz2 /dev/sda /dev/sdb /dev/sdc /dev/sdd /dev/sde

After a disk failure, ZFS starts resilvering, which rebuilds data on the replacement disk. The resilvering progress can be monitored using the zpool status command:

# Check resilvering progress
$ sudo zpool status

Regular scrubbing ensures data integrity by checking for errors and correcting them using redundant data. Scrubs can be scheduled with cron:

# Schedule a scrub every Sunday at 2 AM
0 2 * * 7 sudo zpool scrub mypool

ZFS in Virtualized Environments

ZFS is often used as the underlying storage for virtual machines in environments like VMware and KVM. Its features, such as snapshots, cloning, and compression, help manage virtual machine data effectively.

ZFS with VMware

VMware typically uses NFS as a shared storage protocol. ZFS can act as the backend storage for NFS datastores. To configure ZFS as NFS storage for VMware, export the ZFS dataset over NFS:

# Share a ZFS dataset over NFS for VMware
$ sudo zfs set sharenfs=on mypool/vmstorage

VMware hosts can mount the ZFS NFS share as a datastore. ZFS snapshots provide point-in-time copies of VM data, allowing quick backups and restores. To take a snapshot of a VM storage dataset:

# Take a snapshot of a VM storage dataset
$ sudo zfs snapshot mypool/vmstorage@vmbackup

ZFS cloning allows multiple VMs to be created from a single base image. This reduces storage overhead and improves efficiency:

# Create a clone of a VM base image
$ sudo zfs clone mypool/vmstorage@vmbackup mypool/vmclone

ZFS with KVM (Kernel-based Virtual Machine)

ZFS integrates well with KVM as the storage backend for virtual machines using ZVOLs, which are block storage devices that support ZFS features such as compression and snapshots. A ZVOL can be created and presented to KVM as a virtual block device:

# Create a 50GB ZVOL for KVM VM
$ sudo zfs create -V 50G mypool/kvmvol

ZFS’s thin provisioning allocates space only as data is written, optimizing storage usage. Snapshots of ZVOLs can be taken before major changes to KVM virtual machines. To take a snapshot of a ZVOL:

# Take a snapshot of a ZVOL
$ sudo zfs snapshot mypool/kvmvol@preupdate

If needed, the ZVOL can be rolled back to this snapshot:

# Rollback to the snapshot
$ sudo zfs rollback mypool/kvmvol@preupdate