Zvol Snapshot, Use the Dataset dropdown list to select an existing ZFS pool, dataset, or zvol to snapshot. These features can save massive amounts of time dealing with storage configurations. And then make sure either child dataset replication is enabled on vol1 or create a separate replication task for your zvol. You cannot create a clone of a To list all available snapshots, run ls in the file system’s . I want to create snapshot of the ZVOL at a specific time. What is the best way to clone those snapshots from the backup pool to a new complete zvol on Pool3, do I need to first replicate the snapshots with zfssend to pool3, then promote it? Once you have the ZVOL, you have a raw block storage device to interact with – think mkfs. Ideal for beginners. Disk Space Accounting for ZFS Snapshots When a snapshot is created, its disk space is initially shared between the snapshot and the file system, and possibly with previous snapshots. As the file system changes, space that was previously shared becomes unique to the snapshot, and thus is counted in the snapshot's used property. Examples: ZFS, Ceph RBD, thin LVM, … So it seems with a large zvol I give up granular control over snapshots at the VM level? Just to add to my confusion - each vm on the PM side has a snapshot option. So far, when dealing with the ZFS filesystem, other than creating our pool, we haven't dealt with block devices at all, even when mounting the datasets. Importing a Disk: import a single disk that is formatted with the UFS, NTFS, MSDOS, or EXT2 filesystem. ZFS is licensed under the Common Development and Distribution License (CDDL). zfs/snapshot directory. 1k次。本文介绍如何利用ZFS的ZVOL特性创建块设备，并在此基础上进行分区、文件系统创建、快照及回滚等操作。ZVOL允许用户将ZFS的功能应用于裸块设备，提供快照、克隆等高级功能。 Short version: 1- I'm trying to copy a zvol used for iscsi over to a new dataset. For this to be accurate, you'd need to have created a zvol, formatted it with another filesystem (eg ext4), then put a raw file on it, then used that raw on ext4 on zvol as a backing. Hello Freenas Community I have an issue where a user has accidentally altered contents of shared directory in Windows environment. With regular ZFS datasets, I can easily restore files by browsing the snapshot files at /. Dog help you if you ask the documentation’s stupid AI assistant how to restore a VM from a zvol snapshot. There is a property called snapdev which will expose the snapshots of a volume. zfs - 配置 ZFS 文件系统 zfs 命令按照 zpool (8) 中描述的方式配置 ZFS 存储池中的 ZFS 数据集。数据集由 ZFS 名称空间中的唯一路径进行标识。例如： The correct statement is that just like normal dataset snapshots, snapshots of a zvol only take up as much space as the size of the data blocks that have changed since the snapshot. Datasets are listed, one on each line, by zfs list. To do my backups, I do a snapshot of this zvol on a Discover ZFS basics, including pools, snapshots, performance tuning, and best practices for effective system administration. 文章浏览阅读1. I'm trying to mount a snapshot of a ZFS zvol. File: Browse to an existing file. A zfs snapshot is a read-only copy of a ZFS dataset or zvol. Is it possible to restore a single file from the snapshot of a zvol? Said zvol is used by a virtual machine. 3 U3. Sorry for being verbose. A ZVOL is a "ZFS volume" that has been exported to the system as a block device. So, my question is how do I go about creating a point in time copy or a snapshot of said ZVOL, set it to RW and then attach it to my linux machine. Recovering a VM back to a specific snapshot of its zvol is an exercise left to the reader. Snapshots Creating Snapshots A zfs snapshot is a read-only copy of a ZFS dataset or zvol. The directory is served to windows server via iSCSI from a FreeNAS based ZVOL on TANK1 We do daily snapshots of the ZVOLs as well as replications w/snapshots I need to Cloud Sync a snapshot, especially a Zvol snapshot. Device: Select the unformatted disk, controller, zvol, or zvol snapshot. Therefore I also want to create a snapshot after each backup. You can also access the Snapshots screen from the Periodic Snapshot Tasks screen. TrueNAS Periodic Snapshots Task Menu Select the ZVol we created earlier under the Dataset section. [10] A ZVOL is a ZFS block device that resides in your storage pool. VM successfully booted without issue using the other volume. You are right, the snapshot size cannot (significantly) exceed the zvol size, here 100GB. I need to Cloud Sync a snapshot, especially a Zvol snapshot. Provides instructions on setting up iSCSI block shares manually or using the wizard and starting the service. To perform a quick snapshot of existing storage, go to Storage > Snapshots and click ADD. What might be a sound approach here and how are snapshots best managed Click on the Tasks menu and then click Periodic Snapshot Tasks and press ADD. 2- Reading suggests I need to take a snapshot first and actually copy that over using zfs send. On a system running Scale is it necessary to do some aditional steps to ensure ZVOL snapshots are consistent besides using the jobs we can schedule using the TrueNAS web interface? The VMs disks are ZVOLs on a ZFS tank. a zvol is fundamentally a file of a fixed size typically it backs a filesystem of a different type (like ntfs or ext4). Currently the only option for snapshot in Freenas is periodic snapshot which is handy but not what I am looking for. You should then be able to copy any and all files you want from the snapshot where ever you want. Just make sure you have enough available space in the zvol to accommodate the change rate of the data in said zvol. ext4 /dev/zvol/poolname/zvolname, for example – but you still get all the normal ZFS features along with it, like data integrity, compression, snapshots, and so forth. These are two things you can’t do with ext4 natively. I have a zvol shared through iSCSI which is formatted as NTFS by the client. I just want to validate that, conceptually, if everything falls into place a VM’s zvol snapshot clone, could be shared as an iSCSI LUN and be booted off from another hypervisor. The zvol should have a ext2 partition on it (as evidenced by the CentOS VM to which the zvol is currently shared by iSCSI): [root@test-vm ~]# file Hi, I use ZVol to export an iSCSI device target to a linux host which creates a dm-crypt with ext4 onto it. The TrueNAS software displays a suggested name that you can override with any custom string. The linux host stores daily backups on it via rsync. I have three FreeNAS Servers (all up2date with 11. If I clone a snapshot and add it in iSCSI as an extent, assign it a target and then try and mount it from a windows machine, the extent is found but it cannot recognise the format and still thinks it is read only. Similar to VMware where you can build trees of snapshots and decide from which to start. Mar 18, 2022 · For everything on a daily/weekly scale I would use BPS "snapshot" mode backups. Disks: view and manage disk options. This means that the single block device gets to take advantage of your underlying RAID array, such as mirrors or RAID-Z. Only displayed when Type is set to Device. ZFS also includes a mechanism for dataset and pool-level snapshots and replication, including snapshot cloning, which is described by the FreeBSD documentation as one of its "most powerful features" with functionality that "even other file systems with snapshot functionality lack". I was thinking in term of comparing the parent dataset used size and the snapshot used size. 1): Supermicro X9DRi-LN4F, Dual E5-2620v2, 64 GB RAM, 4 vdevs with 6x6 TB RAIDZ-2 (some datasets for SMB), Chelsio N320 Card My plan was to create a ZVOL - not VBox snapshots for each Server instance. Each ZVOLS has daily schedule snapshots and replication to another pool on the same system AND to another server. 4- Probably due to my misprovisoning Hi, I have a running system with Virtualbox and one of its disk is a zvol (type dev) attached to it. Snapshots are created almost instantly and initially consume no additional disk space within the pool. Snapshots: manage local snapshots. How can I access these snapshots? I expected I can mount a specific I use ZFS on my laptop on a single disk, because I still have snapshot feature, easy ZFS to ZFS backup and ARC cache available that way. A 100GB zvol can use much less than 100GB and then be smaller than its snapshot if the latter is less compressed. May 22, 2025 · You would need to setup a clone iSCSI share pointing at the snapshot. 本文主要是讲如何把ZFS当作块设备使用–主要是通过ZFS卷（ZVOLS）。使用ZVOLS还可以享受底层ZFS带来的好处，比如有ZFS的数据清理，压缩，去重等等特性。 ZVOL是作为块设备导出到系统的“ZFS卷”。到目前为止，在处理ZFS文件系统时，除了创建池之外，我们根本没有处理块设备，甚至在挂载数据集时也 The USED size of a snapshot (in contrast to my first understanding) does not reflect the amount of data which was written to the ZVOL since that snapshot has been taken, before the next snapshot has been taken. Is there any way to do this form the CLI? Short version: 1- I'm trying to copy a zvol used for iscsi over to a new dataset. (running zvol snapshots on truenas just daily as a secondary security layer) (I guess for clean migration I would in any case have to set it first as cli (iscsi+ext4) in proxmox and in a second step create another iscsi share for copying over the vm image files . Difference between ZVOL Replication and dataset snapshot replication? I really have a hard time understanding the speeds of my replications. Set it on the zvol itself. So there are valid use cases for non-redundant ZFS pools. The Cloud Sync feature offers the possibility to sync from a Snapshot, as far as I understand the option, so it should be possible to do it in another context. Read the article today! There's 3 types of datasets in ZFS: a filesystem following POSIX rules, a volume (zvol) existing as a true block device under /dev, and snapshots thereof. A ZVOL is a ZFS block device that resides in your storage pool. If you have a 15G zvol with 10G of data in it, and you snapshot that, you aren't going to consume 10G or 15G of additional space. . What is the best way to clone those snapshots from the backup pool to a new complete zvol on Pool3, do I need to first replicate the snapshots with zfssend to pool3, then promote it? Hi - I ran into a problem today having deleted some files within one of my Ubuntu VM's running inside of FreeNAS. Is there any way to do this form the CLI? Thanks for the suggestion. Multipaths: View multipath information for systems with compatible hardware. ) Snapshots: manage local snapshots. It is possible to create another file system on it (including swap) or use it as storage device for virtual machines, like any other block device. Since we have limited space in our Zpool, we are going to change the Snapshot Lifetime to 1 week, but leave the schedule set to daily at midnight. VMware-Snapshots: coordinate OpenZFS snapshots with a VMware datastore. For example, to see the snapshot taken: The USED size of a snapshot (in contrast to my first understanding) does not reflect the amount of data which was written to the ZVOL since that snapshot has been taken, before the next snapshot has been taken. Any idea how There is a property called snapdev which will expose the snapshots of a volume. Also keep in mind that PVE only allows you to rollback to the latest zfs snapshot. Then from windows connect to it, and you would be looking at the iSCSI drive at the point in time of the snapshot. Did you mean that it's a raw file on a dataset? Functionality like snapshots are provided by the storage layer itself. As the file system changes, disk space that was previously shared becomes unique to the snapshot, and thus is counted in the snapshot's used property. 3- I'm stuck not able to take a snapshot (not enough space error). Just keep in mind if you have a lot of snapshots this can result in an explosion of device nodes being created. The new dataset is the same type (for example, file system or volume) as the snapshot from which the clone was created. This works great and snapshots are taken of the zvol daily. Enter the desired size of the zvol in Size. If Create New is selected, use the browser to select an existing pool or dataset to store the new zvol. trying to read the zvol while it's in use is not going to work. What is the best way to clone those snapshots from the backup pool to a new complete zvol on Pool3, do I need to first replicate the snapshots with zfssend to pool3, then promote it? ZFS has massive amounts of utility to Linux users - ZVols, LZ4 Compression support, ARC/L2ARC and ZIL caching, and much more. To clone a zvol from an existing snapshot, select the zvol on the Datasets tree table, then click Manage Snapshots on the Data Protection widget to open the Snapshots screen. Wouldn't the snapshots only contain recent changes to the data and not everything required for a complete restore? EDIT: Never mind, I just tested moving a recursive snapshot from one volume to another and rolling it back. Either enable recursive snapshots on vol1, or create a new snapshot for the zvol. Snapshots of the zvol however are taken daily of the Zvol. Wait, what? A zvol is a simple block/character device, not a filesystem. When a snapshot is created, its space is initially shared between the snapshot and the file system, and possibly with previous snapshots. Copy-on-write, snapshots, data integrity verification and automatic repair (scrubbing), RAID-Z, a maximum 16 exabyte file size, a maximum 256 quadrillion zettabyte storage with no limit on number of filesystems (datasets) or files [1]. I use ZFS on my laptop on a single disk, because I still have snapshot feature, easy ZFS to ZFS backup and ARC cache available that way. Creating a ZFS Clone To create a clone, use the zfs clone command, specifying the snapshot from which to create the clone, and the name of the new file system or volume. 4- Probably due to my misprovisoning In this guide, you can learn about the management of Zpools, which are the basic structure of the ZFS-based data storage systems. You probably didn’t notice, but you just enabled transparent compression and took a snapshot of your ext4 filesystem. The new file system or volume can be located anywhere in the ZFS hierarchy. Its about 500gb of data, I verified the snapshots are there for the date needed on my backup pool. They are a valuable tool both for system administrators needing to perform backups and other users who need to save the state of their file system at a particular point in time and possibly restore it ZVOL is a kind of block device whose space is allocated from the pool. zfs/snapshot/, but zvols, I can't even see them in the virtual_machines dataset where they're Its about 500gb of data, I verified the snapshots are there for the date needed on my backup pool. Aug 5, 2025 · To clone a zvol from an existing snapshot, select the zvol on the datasets tree table, then click View Snapshots on the Data Protection widget to open the Snapshots screen. How do I roll back a snapshot of the zvol? The snapshots for zvols I thought were stored within the zvol. Bottom line: if you need to take a snapshot of a zvol, you need to take a snapshot of a zvol. Jan 29, 2018 · So the answer to the question is: You can access the snapshots using the devices in /dev/zvol/zfspool or those in /dev, provided you have made them visible by setting the snapdev property for the ZVOL in question to visible. Select Create New for options to create a new zvol. Restore. Tutorials for configuring ZFS snapshot replication tasks in TrueNAS. y3gdy, bsp6o, m2djl, m2ple, x5nks, ajjiws, okhdx, hxddj, 4rqw3, 7qo1,