How many drives do I need for ZFS? (2023)

How many drives does ZFS need?

You need at least two disks for a single-parity RAID-Z configuration and at least three disks for a double-parity RAID-Z configuration. For example, if you have three disks in a single-parity RAID-Z configuration, parity data occupies disk space equal to one of the three disks.

ZFS does prefer to use the raw drive so ideally this means drives of the same size. But if you have a 750GB and a 500GB you can slice the 750GB to create a 500GB slice and use that slice in the pool.

ZFS's equivalent is RAIDZ2. It is a fairly safe RAID level because it has the ability to withstand two drive failures and still rebuild, meaning if one fails you can still withstand another drive failure before or while rebuilding without losing your pool.

raidz2 requires at least four disks and will use two(2) disks of space for parity. raid7 or raidz3 distributes parity just like raid 5 and 6, but raid7 can lose three physical drives.

Using more than 12 disks per vdev is not recommended. The recommended number of disks per vdev is between 3 and 9. If you have more disks, use multiple vdevs.

Because ZFS is also the filesystem it is aware of the FS. So if I have a mirror that is 95% free space and I replace a drive ZFS knows to only copy the 5% of actual data. HW Raid controllers are blind to the FS and have no way of distinguishing free space (or, previously used but since freed space) from data.

You can add more vdevs to a zpool , and you can attach more disks to a single or mirror vdev .

A zpool contains one or more vdevs , each of which in turn contains one or more devices . Zpools are self-contained units—one physical computer may have two or more separate zpools on it, but each is entirely independent of any others. Zpools cannot share vdevs with one another.

For example, if you run a ZFS pool based on a single 3-disk RAIDZ vdev (RAID5 equivalent ²), the only way to expand a pool is to add another 3-disk RAIDZ vdev ¹. You can't just add a single disk to the existing 3-disk RAIDZ vdev to create a 4-disk RAIDZ vdev because vdevs can't be expanded.

Using 2 drives would be ideal, and in your case you could setup a mirror, which is very easy in TrueNAS. It goes without saying, that having an SSD for the TrueNAS install is the norm, ideally 2 that are mirrored (an option during the install process).

Does ZFS defrag?

Mainly because there's no notion of online defragmentation in ZFS. That's really only possible by copying the pool data to another pool or rewriting to new storage.

A minimum of 2 GB of free memory is required to run ZFS, however it is recommended to use ZFS on a system with at least 8 GB of memory.

With raidz, you can loose one drive and not loose data. a raidz2 is basically a raid6, not a raid 0+1. Instead of one disk being able to reconstruct any lost disk like in raidz, there are 2 disks that can be used. with raidz2, you can loose 2 drives and not loose data.

RAIDZ1, RAIDZ2 and RAIDZ3 are fault tolerant to a different degree - should one of the hard drives in the array fail, the data is still reconstructed on the fly and no access interruption occurs. There are some more complex layouts, which are combinations of basic RAIDZ levels.

The file system compression feature compresses the files stored on the file system automatically to save the precious disk space of your storage device. Like many other file systems, the ZFS file system also supports file system-level compression.

Pooled Storage

Unlike most files systems, ZFS combines the features of a file system and a volume manager. This means that unlike other file systems, ZFS can create a file system that spans across a series of drives or a pool. Not only that but you can add storage to a pool by adding another drive.

ZFS is a filesystem which does waaaay more than LVM does as a container. It's not just that it's "cool". Rapid filesystem snapshots, checksums, dedupe, do some research and you'll see why it's recommended. LVM does snapshots & checksums.

ZFS is a highly reliable filesystem which uses checksumming to verify data and metadata integrity with on-the-fly repairs. It uses fletcher4 as the default algorithm for non-deduped data and sha256 for deduped data.

While ext4 comes embedded on Linux, it may not be the right choice for managing your data. Consider the strengths of each system in light of your needs. On the face of it, ZFS seems better but arrives with much higher hardware requirements to run smoothly.

You can dynamically add disk space to a pool by adding a new top-level virtual device. This disk space is immediately available to all datasets in the pool. The virtual device that you add should have the same level of redundancy as the existing virtual device.

How do I replace ZFS drive?

Sad as it makes me, as of 2017, ZFS is the best filesystem for long-term, large-scale data storage. Although it can be a pain to use (except in FreeBSD, Solaris, and purpose-built appliances), the robust and proven ZFS filesystem is the only trustworthy place for data outside enterprise storage systems.

ZFS filesystems are built on top of virtual storage pools called zpools. A zpool is constructed of virtual devices (vdevs), which are themselves constructed of block devices: files, hard drive partitions, or entire drives, with the last being the recommended usage.

Using more than 12 disks per vdev is not recommended. The recommended number of disks per vdev is between 3 and 9. With more disks, use multiple vdevs. Some older ZFS documentation recommends that a certain number of disks is needed for each type of RAIDZ in order to achieve optimal performance.

Mirror vdevs

As mirrors keep identical copies of the data in several disks, they can provide the best IOPS, the number of read and/or write operations that can be performed per second. ZFS distributes the writes amongst the top level vdevs, so the more vdevs in the pool, the more IOPS that are available.

However, accumulating all the associated pros and cons of external hard drives, there should be at least one external hard drive in the minimum scenario. But in a much better case, there should be two external hard drives.

With 8GiB of RAM, you'll have enough to run your system and the jails - plex, owncloud, and a small Debian VM. Just. Barely. You won't have RAM left in any meaningful capacity for read cache, and that'll slow you down.

You can install and run TrueNAS without any data device, but we strongly discourage it. TrueNAS does not require two cores, as most halfway-modern 64-bit CPUs likely already have at least two. For help building a system according to your unique performance, storage, and networking requirements, read on!

How often should you scrub ZFS?

It's best practice to schedule at least one scrub a month, and some may want to do it as often is even one time a week, although this isn't completely necessary.

The scrub examines all data in the specified pools to verify that it checksums correctly. For replicated (mirror, raidz, or draid) devices, ZFS automatically repairs any damage discovered during the scrub.

ZFS is a COW(copy on write) file system. Data is fragmented all over the disks as part of the design of the file system. Every write is a new "fragment". The "frag" has to do with the free space on the drive and should be ignored.

ZFS is the only filesystem option that is stable, protects your data, is proven to survive in most hostile environments and has a lengthy usage history with well understood strengths and weaknesses. ZFS has been (mostly) kept out of Linux due to CDDL incompatibility with Linux's GPL license.

There is no OS level support for ZFS in Windows. As other posters have said, your best bet is to use a ZFS aware OS in a VM.

1 Answer. ZFS is great on servers with lots of ram, lots of cpu, and lots of disks. It does very well on large disks and joining multiple disks, and has nice features like software implementation of hybrid spinning rust + SSD cache raid volumes for extra performance.

raidz1 is fine as long as you have scrubs set to run on any kind of schedule, and get a notice if the scrub finds anything. All other knocks against raidz1 are from people who don't understand the difference between RAID and raidz.

ZFS works in 128kb blocks, generally. So ZFS writes a 128kB block - to a 16-drive RAID6 array. In the configuration you're proposing, that means the RAID controller needs to read almost 7 MB from the array and recompute the parity across those 7 MB. Then rewrite that entire 7 MB back to disk.

RAID 6, also known as double-parity RAID (redundant array of independent disks), is one of several RAID schemes that work by placing data on multiple disks and allowing input/output (I/O) operations to overlap in a balanced way, improving performance.

RAID 7 is a trademarked RAID level owned by the now defunct Storage Computer Corp. It is a non-standard RAID level that requires proprietary hardware. RAID 7 is based on RAID 3 and RAID 4, but adds caching.

Is Unraid better than RAID?

In a direct Unraid vs Raid comparison, Unraid may not be as performant as traditional RAID, but it's far more efficient. There is a massive reduction in power consumption because all the drives aren't spinning to read and write data. Unraid is also efficient in how you can expand the size of the array.

There is no direct path from RAIDZ1 to RAIDZ2. You can add a new VDEV of the same configuration to the existing pool as you said* or you will have to back up your data, destroy the existing pool, create a new pool with a RAIDZ2 VDEV with the old and new drives on the new server and then restore your data.

Copy-on-write in ZFS isn't only at the filesystem level, it's also at the disk management level. This means that the RAID hole—a condition in which a stripe is only partially written before the system crashes, making the array inconsistent and corrupt after a restart—doesn't affect ZFS.

The deduplication feature of the ZFS filesystem is a way of removing redundant data from ZFS pools/filesystems. Simply put, if you store a lot of files on your ZFS pool/filesystem, and some of these files are the same, only one copy of these files would be kept on the ZFS pool/filesystem.

Using 2 drives would be ideal, and in your case you could setup a mirror, which is very easy in TrueNAS. It goes without saying, that having an SSD for the TrueNAS install is the norm, ideally 2 that are mirrored (an option during the install process).

While ext4 comes embedded on Linux, it may not be the right choice for managing your data. Consider the strengths of each system in light of your needs. On the face of it, ZFS seems better but arrives with much higher hardware requirements to run smoothly.

Sad as it makes me, as of 2017, ZFS is the best filesystem for long-term, large-scale data storage. Although it can be a pain to use (except in FreeBSD, Solaris, and purpose-built appliances), the robust and proven ZFS filesystem is the only trustworthy place for data outside enterprise storage systems.

ZFS redundancy is at the vdev level, not the zpool level. There is absolutely no redundancy at the zpool level—if any storage vdev or SPECIAL vdev is lost, the entire zpool is lost with it.

However, accumulating all the associated pros and cons of external hard drives, there should be at least one external hard drive in the minimum scenario. But in a much better case, there should be two external hard drives.

Can you run TrueNAS with 8gb RAM?

With 8GiB of RAM, you'll have enough to run your system and the jails - plex, owncloud, and a small Debian VM. Just. Barely. You won't have RAM left in any meaningful capacity for read cache, and that'll slow you down.

You can install and run TrueNAS without any data device, but we strongly discourage it. TrueNAS does not require two cores, as most halfway-modern 64-bit CPUs likely already have at least two. For help building a system according to your unique performance, storage, and networking requirements, read on!

Have enough memory: A minimum of 2GB of memory is recommended for ZFS. Additional memory is strongly recommended when the compression and deduplication features are enabled. Improve performance by setting ashift=12: You may be able to improve performance for some workloads by setting ashift=12 .

You must not use it on a dual boot system though because it will erase the entire disk.

StorNext is Officially the Fastest File System in the World for Video Workloads.

Pooled Storage

Unlike most files systems, ZFS combines the features of a file system and a volume manager. This means that unlike other file systems, ZFS can create a file system that spans across a series of drives or a pool. Not only that but you can add storage to a pool by adding another drive.

There is no OS level support for ZFS in Windows. As other posters have said, your best bet is to use a ZFS aware OS in a VM.

To complicate matters, ZFS offers features found in few production-ready Linux file systems. The only file system that comes close is Btrfs, which has been often maligned as not being stable enough for production systems.

ZFS is a highly reliable filesystem which uses checksumming to verify data and metadata integrity with on-the-fly repairs. It uses fletcher4 as the default algorithm for non-deduped data and sha256 for deduped data.

ZFS is actually not just a filesystem; it's a suite of tools and a volume manager with RAID capabilities. Instead of mixing ZFS RAID with hardware RAID, it is recommended that you place your hardware RAID controller in JBOD mode and let ZFS handle the RAID.

Is synology a ZFS?

Synology is on BTRFS, Qnap has ZFS.... but their software has the worst security record. ( Arguably worst than Western Digital ) And TrueNAS mini isn't really a consumer NAS at all. The closet thing would be something like a Helios64 [1] from Kobol. But they dont seems to ship things anymore.