What is ZFS?
ZFS is a file system and volume manager in one. It turns the disks in a server into a storage pool, checks everything it reads for corruption, and can copy snapshots to another machine.
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What it is
Sun Microsystems created ZFS for Solaris. After Oracle bought Sun, the open source code carried on as OpenZFS, which runs on Linux and FreeBSD and is built into Proxmox VE and TrueNAS. Because it manages the disks and the file system together, it knows which disk holds which copy of your data and can fix a bad copy from a good one.
The ideas worth knowing
- Pools, mirrors and RAID-Z: disks are grouped into a pool. A mirror keeps identical copies on two or more disks. RAID-Z uses parity and, depending on the level, survives one, two or three failed disks per group.
- Checksums: every block has a checksum, so ZFS notices when a disk silently returns damaged data and repairs it from a redundant copy. A scheduled scrub checks the whole pool.
- Snapshots: a frozen view of a file system or virtual disk, created almost instantly and using space only as the data changes.
- Send and receive: snapshots stream to another ZFS machine. After the first full copy, only changes travel.
- Compression: data can be compressed as it is written. LZ4, the usual method, adds little processor load.
- Direct disk access and memory: ZFS should see each disk directly, not through a hardware RAID volume. It caches reads in spare memory, so a server short of memory feels slow.
ZFS compared with Ceph
ZFS is storage inside one server. If that server stops, so does its pool, though a replica on a second server can take over without the latest changes. Ceph spreads storage across several servers so losing one stops nothing, at the cost of more hardware and care. Our storage service page explains when each fits. Neither replaces a backup.
How KawaConnect works with ZFS
We run Proxmox and Ceph for our own infrastructure and build Proxmox servers for clients. ZFS is the storage built into Proxmox, and for a single host or a pair it is where our design starts. When storage must keep running through the loss of a whole server, we plan Ceph.
Related services
Ceph and ZFS storage
Choosing, building and looking after business storage.
Proxmox consulting
Virtualization hosts on ZFS or Ceph.
Backup and disaster recovery
The separate copy snapshots cannot replace.
Learn more
- OpenZFS documentationThe official manual, with setup guides per operating system and command reference pages.
- OpenZFS project siteProject news, supported platforms, and how the developers work together.
- ZFS on WikipediaA neutral history from Sun to OpenZFS and an overview of the features.
- ZFS on Linux in the Proxmox VE wikiHow Proxmox VE uses ZFS, including pool layouts, memory settings and replacing a failed disk.
Planning storage for a Proxmox server
Tell us how many servers you have and what runs on them, and we will recommend ZFS, Ceph or both.
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