Upon reboot, use your user credentials to log in with. Then verify the install with the command below. As an advanced, next-generation filing system, ZFS has a lot to offer. Some of the features that newer versions have are:.
I am a freelancing software project developer, a software engineering graduate and a content writer. I love working with Linux and open-source software. These are the minimum specs, and you should definitely allot more resources to your ZFS. Then type in the hostname for your system, and click OK. Just leave it as is and click select.
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Thread starter patovm04 Start date Jun 7, Tags dual boot gpt root on zfs uefi. Important notes: 1 This tutorial assumes you have the OS you want to dual-boot with already installed on your drive, and that you already have freed up some disk space. As always, make sure to disable Secure Boot and Fast Boot. Change it according to your setup, if needed. Run gpart show to be sure. I personally recommend rEFInd, but I won't detail how to install it here. Just gonna show you how the respective entries should look like in each case.
This tutorial is not an unsafe procedure if you understand what you're doing especially in regards to selecting the correct disk where you want to install. Anyway, do it at your own risk! Proceed installing as usual, until you reach the "Partitioning" stage. Here I share some sample entries to guide you a bit. Last edited: Feb 12, What can i do? Displaying both the dataset and the snapshot together reveals how snapshots work in COW fashion.
They save the changes delta made and not the complete file system contents all over again. This means that snapshots take little space when making changes. Observe space usage even more by copying a file to the dataset, then creating a second snapshot:. The second snapshot contains the changes to the dataset after the copy operation. This yields enormous space savings.
ZFS provides a built-in command to compare the differences in content between two snapshots. This is helpful with a lot of snapshots taken over time when the user wants to see how the file system has changed over time. For example, zfs diff lets a user find the latest snapshot that still contains a file deleted by accident.
Doing this for the two snapshots created in the previous section yields this output:. The first column shows the change type:. Comparing two snapshots is helpful when using the ZFS replication feature to transfer a dataset to a different host for backup purposes.
A backup administrator can compare two snapshots received from the sending host and determine the actual changes in the dataset. See the Replication section for more information. When at least one snapshot is available, roll back to it at any time. Most often this is the case when the current state of the dataset is no longer and if preferring an older version.
Scenarios such as local development tests gone wrong, botched system updates hampering the system functionality, or the need to restore deleted files or directories are all too common occurrences. To roll back a snapshot, use zfs rollback snapshotname. If a lot of changes are present, the operation will take a long time. During that time, the dataset always remains in a consistent state, much like a database that conforms to ACID principles is performing a rollback.
This is happening while the dataset is live and accessible without requiring a downtime. Once the snapshot rolled back, the dataset has the same state as it had when the snapshot was originally taken.
Rolling back to a snapshot discards all other data in that dataset not part of the snapshot. Taking a snapshot of the current state of the dataset before rolling back to a previous one is a good idea when requiring some data later.
This way, the user can roll back and forth between snapshots without losing data that is still valuable. In the first example, roll back a snapshot because of a careless rm operation that removes too much data than intended. At this point, the user notices the removal of extra files and wants them back.
ZFS provides an easy way to get them back using rollbacks, when performing snapshots of important data on a regular basis.
To get the files back and start over from the last snapshot, issue the command:. The rollback operation restored the dataset to the state of the last snapshot. Rolling back to a snapshot taken much earlier with other snapshots taken afterwards is also possible. When trying to do this, ZFS will issue this warning:.
This warning means that snapshots exist between the current state of the dataset and the snapshot to which the user wants to roll back. To complete the rollback delete these snapshots.
ZFS cannot track all the changes between different states of the dataset, because snapshots are read-only. ZFS will not delete the affected snapshots unless the user specifies -r to confirm that this is the desired action. If that is the intention, and understanding the consequences of losing all intermediate snapshots, issue the command:. The output from zfs list -t snapshot confirms the removal of the intermediate snapshots as a result of zfs rollback -r.
Snapshots live in a hidden directory under the parent dataset:. By default, these directories will not show even when executing a standard ls -a. The property named snapdir controls whether these hidden directories show up in a directory listing. Setting the property to visible allows them to appear in the output of ls and other commands that deal with directory contents.
Restore individual files to a previous state by copying them from the snapshot back to the parent dataset. The directory structure below. The next example shows how to restore a file from the hidden. Even if the the snapdir property is set to hidden, running ls. The administrator decides whether to display these directories. This is a per-dataset setting. Copying files or directories from this hidden. Trying it the other way around results in this error:.
The error reminds the user that snapshots are read-only and cannot change after creation. Copying files into and removing them from snapshot directories are both disallowed because that would change the state of the dataset they represent. Snapshots consume space based on how much the parent file system has changed since the time of the snapshot.
The written property of a snapshot tracks the space the snapshot uses. To destroy snapshots and reclaim the space, use zfs destroy dataset snapshot. Adding -r recursively removes all snapshots with the same name under the parent dataset. Adding -n -v to the command displays a list of the snapshots to be deleted and an estimate of the space it would reclaim without performing the actual destroy operation.
A clone is a copy of a snapshot treated more like a regular dataset. Unlike a snapshot, a clone is writeable and mountable, and has its own properties. After creating a clone using zfs clone , destroying the originating snapshot is impossible.
Promoting a clone makes the snapshot become a child of the clone, rather than of the original parent dataset. This will change how ZFS accounts for the space, but not actually change the amount of space consumed. Mounting the clone anywhere within the ZFS file system hierarchy is possible, not only below the original location of the snapshot.
A typical use for clones is to experiment with a specific dataset while keeping the snapshot around to fall back to in case something goes wrong. After achieving the desired result in the clone, promote the clone to a dataset and remove the old file system. Removing the parent dataset is not strictly necessary, as the clone and dataset can coexist without problems. Creating a clone makes it an exact copy of the state the dataset as it was when taking the snapshot.
Changing the clone independently from its originating dataset is possible now. The connection between the two is the snapshot. ZFS records this connection in the property origin. Promoting the clone with zfs promote makes the clone an independent dataset. This removes the value of the origin property and disconnects the newly independent dataset from the snapshot. This example shows it:. After making some changes like copying loader.
Instead, the promoted clone can replace it. To do this, zfs destroy the old dataset first and then zfs rename the clone to the old dataset name or to an entirely different name. The cloned snapshot is now an ordinary dataset.
It contains all the data from the original snapshot plus the files added to it like loader. Clones provide useful features to ZFS users in different scenarios. For example, provide jails as snapshots containing different sets of installed applications.
Users can clone these snapshots and add their own applications as they see fit. Once satisfied with the changes, promote the clones to full datasets and provide them to end users to work with like they would with a real dataset. This saves time and administrative overhead when providing these jails. Keeping data on a single pool in one location exposes it to risks like theft and natural or human disasters. Making regular backups of the entire pool is vital. ZFS provides a built-in serialization feature that can send a stream representation of the data to standard output.
Using this feature, storing this data on another pool connected to the local system is possible, as is sending it over a network to another system. Snapshots are the basis for this replication see the section on ZFS snapshots. The commands used for replicating data are zfs send and zfs receive. The pool named mypool is the primary pool where writing and reading data happens on a regular basis. Using a second standby pool backup in case the primary pool becomes unavailable.
Note that this fail-over is not done automatically by ZFS, but must be manually done by a system administrator when needed. Use a snapshot to provide a consistent file system version to replicate.
After creating a snapshot of mypool , copy it to the backup pool by replicating snapshots. This does not include changes made since the most recent snapshot. Now that a snapshot exists, use zfs send to create a stream representing the contents of the snapshot.
Store this stream as a file or receive it on another pool. Write the stream to standard output, but redirect to a file or pipe or an error appears:. To back up a dataset with zfs send , redirect to a file located on the mounted backup pool. Ensure that the pool has enough free space to accommodate the size of the sent snapshot, which means the data contained in the snapshot, not the changes from the previous snapshot.
The zfs send transferred all the data in the snapshot called backup1 to the pool named backup. To create and send these snapshots automatically, use a cron 8 job. Instead of storing the backups as archive files, ZFS can receive them as a live file system, allowing direct access to the backed up data.
To get to the actual data contained in those streams, use zfs receive to transform the streams back into files and directories. The example below combines zfs send and zfs receive using a pipe to copy the data from one pool to another. Use the data directly on the receiving pool after the transfer is complete.
It is only possible to replicate a dataset to an empty dataset. This saves disk space and transfer time. For example:. Create a second snapshot called replica2. This second snapshot contains changes made to the file system between now and the previous snapshot, replica1. Using zfs send -i and indicating the pair of snapshots generates an incremental replica stream containing the changed data.
This succeeds if the initial snapshot already exists on the receiving side. The incremental stream replicated the changed data rather than the entirety of replica1.
Sending the differences alone took much less time to transfer and saved disk space by not copying the whole pool each time. This is useful when replicating over a slow network or one charging per transferred byte. Specifying -P copies the dataset properties including compression settings, quotas, and mount points. Specifying -R copies all child datasets of the dataset along with their properties.
Automate sending and receiving to create regular backups on the second pool. Sending streams over the network is a good way to keep a remote backup, but it does come with a drawback. Data sent over the network link is not encrypted, allowing anyone to intercept and transform the streams back into data without the knowledge of the sending user.
This is undesirable when sending the streams over the internet to a remote host. Use SSH to securely encrypt data sent over a network connection. To keep the contents of the file system encrypted in transit and on the remote system, consider using PEFS. Change some settings and take security precautions first. ZFS requires the privileges of the root user to send and receive streams.
This requires logging in to the receiving system as root. Use the ZFS Delegation system to allow a non- root user on each system to perform the respective send and receive operations. On the sending system:. To mount the pool, the unprivileged user must own the directory, and regular users need permission to mount file systems.
The unprivileged user can receive and mount datasets now, and replicates the home dataset to the remote system:. Create a recursive snapshot called monday of the file system dataset home on the pool mypool. Then zfs send -R includes the dataset, all child datasets, snapshots, clones, and settings in the stream. Pipe the output through SSH to the waiting zfs receive on the remote host backuphost. Using an IP address or fully qualified domain name is good practice. The receiving machine writes the data to the backup dataset on the recvpool pool.
Adding -d to zfs recv overwrites the name of the pool on the receiving side with the name of the snapshot. Using -v shows more details about the transfer, including the elapsed time and the amount of data transferred. Use Dataset quotas to restrict the amount of space consumed by a particular dataset. Reference Quotas work in much the same way, but count the space used by the dataset itself, excluding snapshots and child datasets.
Similarly, use user and group quotas to prevent users or groups from using up all the space in the pool or dataset. The following examples assume that the users already exist in the system. This will properly set owner and group permissions without shadowing any pre-existing home directory paths that might exist.
User quota properties are not displayed by zfs get all. To remove the quota for the group firstgroup , or to make sure that one is not set, instead use:. As with the user quota property, non- root users can see the quotas associated with the groups to which they belong.
A user with the groupquota privilege or root can view and set all quotas for all groups. To display the amount of space used by each user on a file system or snapshot along with any quotas, use zfs userspace.
For group information, use zfs groupspace. For more information about supported options or how to display specific options alone, refer to zfs 1. Reservations guarantee an always-available amount of space on a dataset. The reserved space will not be available to any other dataset. This useful feature ensures that free space is available for an important dataset or log files.
ZFS provides transparent compression. Compressing data written at the block level saves space and also increases disk throughput. Compression can also be a great alternative to Deduplication because it does not require extra memory.
ZFS offers different compression algorithms, each with different trade-offs. The introduction of LZ4 compression in ZFS v enables compressing the entire pool without the large performance trade-off of other algorithms. The biggest advantage to LZ4 is the early abort feature. If LZ4 does not achieve at least For details about the different compression algorithms available in ZFS, see the Compression entry in the terminology section.
The dataset is using GB of space the used property. Without compression, it would have taken GB of space the logicalused property. This results in a 1. Compression can have an unexpected side effect when combined with User Quotas. User quotas restrict how much actual space a user consumes on a dataset after compression.
If a user has a quota of 10 GB, and writes 10 GB of compressible data, they will still be able to store more data. If they later update a file, say a database, with more or less compressible data, the amount of space available to them will change. This can result in the odd situation where a user did not increase the actual amount of data the logicalused property , but the change in compression caused them to reach their quota limit.
Compression can have a similar unexpected interaction with backups. Quotas are often used to limit data storage to ensure there is enough backup space available. Since quotas do not consider compression ZFS may write more data than would fit with uncompressed backups.
OpenZFS 2. Zstandard Zstd offers higher compression ratios than the default LZ4 while offering much greater speeds than the alternative, gzip. Zstd provides a large selection of compression levels, providing fine-grained control over performance versus compression ratio. One of the main advantages of Zstd is that the decompression speed is independent of the compression level.
For data written once but read often, Zstd allows the use of the highest compression levels without a read performance penalty. Even with frequent data updates, enabling compression often provides higher performance. One of the biggest advantages comes from the compressed ARC feature. This allows the same amount of RAM to store more data and metadata, increasing the cache hit ratio.
ZFS offers 19 levels of Zstd compression, each offering incrementally more space savings in exchange for slower compression. The default level is zstd-3 and offers greater compression than LZ4 without being much slower. Levels above 10 require large amounts of memory to compress each block and systems with less than 16 GB of RAM should not use them.
ZFS supports zstd-fast-1 through zstd-fast , zstd-fast through zstd-fast in increments of 10, and zstd-fast and zstd-fast which provide minimal compression, but offer high performance. If ZFS is not able to get the required memory to compress a block with Zstd, it will fall back to storing the block uncompressed.
This is unlikely to happen except at the highest levels of Zstd on memory constrained systems. When enabled, deduplication uses the checksum of each block to detect duplicate blocks. When a new block is a duplicate of an existing block, ZFS writes a new reference to the existing data instead of the whole duplicate block. Tremendous space savings are possible if the data contains a lot of duplicated files or repeated information. Warning: deduplication requires a large amount of memory, and enabling compression instead provides most of the space savings without the extra cost.
Deduplicating only affects new data written to the pool. Merely activating this option will not deduplicate data already written to the pool.
A pool with a freshly activated deduplication property will look like this example:. A value of 1. The next example copies some system binaries three times into different directories on the deduplicated pool created above. Detecting and deduplicating copies of the data uses a third of the space. The potential for space savings can be enormous, but comes at the cost of having enough memory to keep track of the deduplicated blocks.
Deduplication is not always beneficial when the data in a pool is not redundant. ZFS can show potential space savings by simulating deduplication on an existing pool:.
After zdb -S finishes analyzing the pool, it shows the space reduction ratio that activating deduplication would achieve. In this case, 1. Activating deduplication on this pool would not save any amount of space, and is not worth the amount of memory required to enable deduplication.
If the data is reasonably compressible, the space savings may be good. Good practice is to enable compression first as compression also provides greatly increased performance. Enable deduplication in cases where savings are considerable and with enough available memory for the DDT.
Use zfs jail and the corresponding jailed property to delegate a ZFS dataset to a Jail. To control the dataset from within a jail, set the jailed property. ZFS forbids mounting a jailed dataset on the host because it may have mount points that would compromise the security of the host.
A comprehensive permission delegation system allows unprivileged users to perform ZFS administration functions. A user performing backups can get permission to use replication features. ZFS allows a usage statistics script to run with access to only the space usage data for all users.
Delegating the ability to delegate permissions is also possible. Permission delegation is possible for each subcommand and most properties. A caveat: creating a new dataset involves mounting it. That requires setting the FreeBSD vfs. Another restriction aimed at preventing abuse: non- root users must own the mountpoint where mounting the file system.
If a user has the snapshot permission and the allow permission, that user can then grant the snapshot permission to other users. Use a lower value if the system runs any other daemons or processes that may require memory. The default is one fourth of vfs. Increasing this value will improve performance if the workload involves operations on a large number of files and directories, or frequent metadata operations, at the cost of less file data fitting in the ARC.
The default is one half of vfs. Adjust this value to prevent other applications from pressuring out the entire ARC. The total amount of memory used will be this value multiplied by the number of devices. The value is a power of two. To avoid write amplification and get the best performance, set this value to the largest sector size used by a device in the pool.
Common drives have 4 KB sectors. Using the default ashift of 9 with these drives results in write amplification on these devices. Data contained in a single 4 KB write is instead written in eight byte writes. ZFS tries to read the native sector size from all devices when creating a pool, but drives with 4 KB sectors report that their sectors are bytes for compatibility. Setting vfs. Forcing 4 KB blocks is also useful on pools with planned disk upgrades.
Future disks use 4 KB sectors, and ashift values cannot change after creating a pool. In some specific cases, the smaller byte block size might be preferable.
When used with byte disks for databases or as storage for virtual machines, less data transfers during small random reads. This can provide better performance when using a smaller ZFS record size. A value of 0 enables and 1 disables it.
Prefetch works by reading larger blocks than requested into the ARC in hopes to soon need the data. If the workload has a large number of random reads, disabling prefetch may actually improve performance by reducing unnecessary reads. Adjust this value at any time with sysctl 8. This ensures the best performance and longevity for SSDs, but takes extra time.
If the device has already been secure erased, disabling this setting will make the addition of the new device faster. A higher value will keep the device command queue full and may give higher throughput. A lower value will reduce latency. Limits the depth of the command queue to prevent high latency.
The limit is per top-level vdev, meaning the limit applies to each mirror , RAID-Z , or other vdev independently. This tunable extends the longevity of SSDs by limiting the amount of data written to the device. The granularity of the setting is determined by the value of kern.
Changing this setting results in a different effective IOPS limit. Recent activity on the pool limits the speed of scrub , as determined by vfs. ZFS determins the granularity of the setting by the value of kern. Returning the pool to an Online state may be more important if another device failing could Fault the pool, causing data loss. A value of 0 will give the resilver operation the same priority as other operations, speeding the healing process.
Other recent activity on the pool limits the speed of resilver, as determined by vfs. ZFS disables the rate limiting for scrub and resilver when the pool is idle. The current transaction group writes to the pool and a fresh transaction group starts if this amount of time elapsed since the previous transaction group.
A transaction group may trigger earlier if writing enough data. The default value is 5 seconds. A larger value may improve read performance by delaying asynchronous writes, but this may cause uneven performance when writing the transaction group. Some of the features provided by ZFS are memory intensive, and may require tuning for upper efficiency on systems with limited RAM.
As a lower value, the total system memory should be at least one gigabyte. This expands the kernel address space, allowing the vm. To find the most suitable value for this option, divide the desired address space in megabytes by four. In this example for 2 GB. Increases the kmem address space on all FreeBSD architectures. More than a file system, ZFS is fundamentally different. ZFS combines the roles of file system and volume manager, enabling new storage devices to add to a live system and having the new space available on the existing file systems in that pool at once.
By combining the traditionally separate roles, ZFS is able to overcome previous limitations that prevented RAID groups being able to grow. ZFS file systems called datasets each have access to the combined free space of the entire pool.
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