Zfs zvol blocksize. 1 with 4x20TB HDDs in raidz2 configuration.

Zfs zvol blocksize i'm creating zvols for iSCSI. these are by default created with a "block size" of ZFS defaults on proxmox are 8K blocksizes (no joke), I think your statistics primarily show that one shouldn't use those small blocksizes :P Anyhow, what is interesting:If I consider zvols with blocksize x, comparable with a ZFS + QCOW system with equal blocksize x. I don’t know what to conclude, it is harder to say when the baseline speeds are so much lower. This looks like an upstream ext[234] issue. I am using ZFS with an NTFS ZVOL instead of ZFS dataset+samba because the game can't load How does one create a zvol that uses as much of a volume as possible? (I'm aware that performance will go down due to fragmentation if I fill the zvol more than 50% and will avoid that) IE, given a specific volume size that's reported by FreeNAS, is there a way to calculate the max zvol size After using client side tools to resize the partition/filesystem (and placed to the front of the disk, of course) you can use zfs set volsize=50T r10/zvol1 to truncate your zvol. With ZFS, compression is completely transparent. Jun 24, 2024 Wenn er etwas in den ZVOL schreibt, z. 例如, 创建1G的一个块设备, 在zptest池中, 命名为disk1 : I think PE Size is the block size, but I'm not sure. Do a backup . It is important to set the ZVOL block size to match the system page size, which can be obtained by the getconf PAGESIZE command (default on x86_64 is 4KiB). You can't do this from the GUI because too many users probably would try to shrink their volume without first shrinking the client partition. Step 1: Create a volume dataset (zvol) for use as a swap device zfs create -V 4G -b $(getconf PAGESIZE) -o compression=zle \ -o logbias=throughput -o sync=always \ -o primarycache=metadata -o secondarycache=none \ -o com. For example: I gather a ZFS filesystem uses a variable block size, between ashift and recordsize, but that the block size of a zvol is fixed to volblocksize. To manually change this value, use the Block size dropdown list. bdev_block_size (and journal_block_size and rocksdb_block_size among others) For the zvol, it entirely depends on the anticipated access patterns. 创建一个给定大小的卷。The volume is exported as a block device in /dev/zvol/{dsk,rdsk}/path, where path is the name of the volume in the ZFS namespace. Creates a volume of the given size. A. I don't know if there any LVM experts here but it appears that the block size is 4MB. If you made a zvol with a volblocksize of 16k and set special_small_blocks to 16k, no data blocks from that zvol will ever end up on the special vdev no matter how tiny. e. (Where the block size is set by the recordsize hi, i have freenas box with 4 disks in RAID10 for storage. It gets to take advantage of online scrubbing, compression and data The recordsize property just defines an upper limit, files can still be created with smaller block size. For example, in the situation I have described in the question linked above, I could create a ZFS is about the most complex filesystem for single-node storage servers. In order to change the recordsize of existing files, you must actually re-write the existing files. For each machine, I created a first partition of 50 MB with an NTFS cluster size of 4k (to boot) and a second partition with 128k. No tuning at all, no jumbo frames. For media files or other large, sequential workloads, a larger recordsize (1 MB or volblocksize 4K bytes is the best fit optimal solution for mirror zpool created on top of two NVMe formatted with 4K block size. Before I populate the pool with data, it would be great to get a 3rd party “sanity check”, on whether this dataset & zvol layout looks okay. It seems that you need to keep the blocksize smaller than the page size for ext[234]. Keep in mind that the recommended ZFS zvol block size for Linux is 128k, whereas it's 8k-32k under Solaris and variants. This has a secondary benefit of being able to control which ARC does the caching. 10. ext4 with block size 4k is mounted with stripe=4. This throws me off. (ZVOL native read speeds are in the range of 300MB/s single thread) Now here comes the funny part, setting cache=writeback, DOUBLES the read speed. Jup. Speed and free space. Also, built into the ZFS spec is a caveat that you do NOT allow your ZVOL to get over 80% in use While your normal datasets behave like a partition that can be mounted and unmounted and you can directly put files onto it after mount, a zvol behaves like a raw block device. steamdb. The currently available code allows the administrator to tune the maximum block size used as certain workloads do not perform well with large blocks. while the zfs create command doesn't specify blocksize (lacks -b, I'm not sure what the default is, might also be inherited). If you use ZFS with zvols, you may have discovered they can be slow. Is the ZVOL 8 kB block size the most performant option (iSCSI+ZFS) with a VMFS-5 volume? The ZVOL Block Size Modifier is here to facilitate this transformation, but with a twist: it creates a second copy of your chosen ZVOL with the new block size. And ZFS stores multiple copies of metadata so lowering the block size would make the the data to metadata ratio even worse. This dual-copy I set my zvol block size to 128k. Actually I have a second question with Actually, don’t try to match the iSCSI block size itself to everything else; it can cause problems that are really weird and difficult to debug if you’re using non-512 byte iSCSI block sizes (VMware for example hangs left and right with a 4k iSCSI block size, regardless of the zvol block size). But could be higher. In situations like this the only option is to remove layers & verify. Lots of small IO (think databases)? use a similarly small block size. The overhead is still quite large with a block size of 16K and 32K, but becomes 0 once I reach 128K. DESCRIPTION zfs create [-Pnpuv] [-o property=value]filesystem Creates a new ZFS file system. When using zfs destroy pool/fs ZFS is recalculating the whole deduplication. Today I had a need to create a zvol for doing a data recovery job. Nope, because due to the parity and padding overhead of 100% a 305GiB zvol requires 610GiB of raw disk space to store, and our array is only 600GiB. also interesting - nvme 512 versus 4096 sectors on zfs: 512b NVME block size: ~46k IOPS, ~1700MB/s bandwidth 4k NVME block size: ~75k IOPS, ~1800MB/s bandwidth blocksize is the actual size of a given block in a ZFS pool (whether dataset or zvol). 00G - Notice the used space for the zvol immediately became 1G larger, even though I 我们需要对ZFS的几个基本概念有所了解： Record Size Record Size 也就是通常所说的文件系统的block size。ZFS采用的是动态的Record Size，也就是说ZFS会根据文件大小选择*适合*的512字节的整数倍作为存储的块大小，最大的RecordSize为128KB。通常没有必要手工设 What is the recommended "Block Size" for ZFS utilizing Windows Server 2019/2022 Clients (KVM)?? Determine your guest blocksize, create the zvol with the correct volblocksize and align the partitions in your guest on this boundary and use the aforedetermined blocksize. what would be the recommended block size for my current setup? my use case is a mix of linux and windows VMs, and some VMs would be running mssql. I'll do more tests if I get extra network cards to do multipath. info is amazing! Increasing a zvol requires adding another vdev to your zvol vdev consists of another storage group, and should contain the same redundancy of the first group. If ZFS is set to a record size of 128k, the zvol is default to 8k, which one is actually used? - some others databases use bigger block size (16 k mysql/percona/maria, 32-64 k mssql) Bigger block = better performance in zfs pools even for non Descriptions of ZFS internals that have an effect on application performance follow. Hi all, I’ve just created my first ZFS pool in TrueNas Scale Electric-Eel-24. For information about using ZFS volumes in a global zone, see Adding ZFS Volumes to a Non-Global Zone. g. In the following example, a 5GB ZFS volume, system1/vol, is created: $ zfs create -V 5gb system1/vol. I am curious how the performance would scale with a ZFS recordsize and qcow2 cluster size of 128k and 1M. is the name of the volume in the ZFS namespace. Unlike many other file systems, ZFS has a variable record size, meaning files are stored as either a single block of varying sizes, or multiple blocks of recordsize blocks. -o property=value Sets the specified property as if the command zfs set property=value was invoked at the same time the dataset was created. C. Whether you see a difference in the real world, who knows. The zvol is set to either 32k or 64k volblocksize. Describe how to reproduce the problem. IO is read and write in the block size (this is just a simplification). A ashift of 12 defines that 4k is the smallest block size ZFS can work with, no matter what your disk would support. You'll reclaim all the free space on the zvol, get a faster block size and compress the whole thing. ZFS Blocksize. On OpenIndiana the other blocksizes give 150-200 MB/s while 8k blocksize zvol attains 250-400 MB/s. The steps. img file be snapshottable if it is stored "as-is" in a zfs dataset? Well, yeah. Block size could have an effect on sequential speeds but it's limited by the network here. In a dataset, the blocksize is either equal to the recordsize (for a file too large to be stored in a single block) or equal to the filesize (for a file small enough to be stored within a single block). Similar to a disk you can find under /dev/disk/by-id/ , just stored under /dev/zvol/pool/. I don't know if ZFS compresses at the block level or record level though. The logical blocksize of a zvol seems to always be 512 byte, despite the fact that volblocksize is set to 4 KB: # zfs get volblocksize data/iscsi NAME PROPERTY VALUE SOURCE data/vol1 volblocksize 4K - # lsblk -o name,min-io,opt-io,phy-se zfs create [-ps] [-b blocksize] [-o property=value] -V size volume. Part of me just wants to blast it out and start over with ext4/LVM, but I do want to learn to use ZFS, and will be using it when I deploy TrueNAS at some point, so I might as well learn it now. The default blocksize TrueNAS automatically recommends a space-efficient block size for new zvols. zfs create [-ps] [-b blocksize] [-o property=value] -V size volume. Proxmox VE (Deutsch/German) . Feb 22, 2023 94 2 13. But the rest of my VMs are on zvols instead of raw disks on a dataset so I want to keep it consistant. It shows that with blocksize x, NTFS allocation size 4K (default) outperforms NTFS allocation size x. If the zvol is ZFS zvol does not unallocate discarded blocks. If data compression (LZJB) is enabled, variable block sizes are used. This will likely lead to write amplification, as a single 4k EC block write will cause a 16k zvol copy/write. The default blocksize for ZFS is 128KiB, meaning ZFS will dynamically allocate blocks of any size from 512B to 128KiB depending on the size of file being written. Alvin2k8 Member. (Trying to learn ZFS while also learning Proxmox/my first hypervisor has been fun. This may take a while, but would give the most accurate answer possible. In the second case, the block may be as small It looks to me that ZFS recordsize = 64k and qcow2 cluster size = 64k performs the best in all the random performance scenarios while the ntfs block size has a much lesser impact. . 78T 1. A ZFS volume is a dataset that represents a block device. Understanding ZFS and its recordsize + compression properties : zfs. chrcoluk $ zfs set volsize=2G rpool/dump $ zfs get volsize rpool/dump NAME PROPERTY VALUE SOURCE rpool/dump volsize 2G - Example 6-11 Resizing the Swap Volume for Immediate Use This example shows how to adjust the size of the swap volume. Since at the very least I'd need to either set the new Value for volblocksize and do a zfs send | zfs receive (or possibly even creating a new ZVOL with the correct Value, then dd it to the new ZVOL), I was wondering if there was also something to be done inside the Guest VM, particularly with regards to mkfs. If a block can be compressed to fit into a smaller block size, the There are examples for databases (block size 4-8 postgres mysql), there are examples for operating systems (block size 16 ext ntfs), for network storage with small files (block size 4), for large file storage (block size 1M). Each entry in the hash table is a record of a unique block in the pool. ) Pool: “elephant” [raidz2, no pool-level encryption] Dataset/Zvol AFAIK <blockio physical_block_size='16384'/> lets the guest know that writes are best with 16k, but it still can write in 512 byte sectors. Test if the performance is good. " After some research I see that messing with the recordsize is hardly ever worth it (unless your workload is # For a ZVol sudo zfs set compression=lz4 poolname/compressedzvol # For a dataset sudo zfs set compression=lz4 poolname/compresseddataset. The ZVOL stores game assets (some compressable, some not at all) and provides it to a Windows machine via iSCSI using tgt. sun:auto-snapshot=false rpool/swap FreeNAS appears to be pulling the logical sector size of 512 and using it as the physical sector size if done via the gui (fdisk reports a 512 sector size for all HDDs used for storage (All are AF HDDs with physical sector sizes of 4k; OS is on a separate SSD, and FreeNAS partitioned it with 512 logical and 512 physical UFS partition) [I've never utilized an I did get confused on the recordsize of the root dataset being a factor; thanks for pointing that out. Here's a more elaborate guide, copied from the zfsonlinux wiki:. But I will go with your assumption that the UI's Block Size is actually volblocksize. As for determining the ZVOL Tests. "Running a ZFS pool on top of a zvol ashift is the minimum (4k = 12) block size that zfs will try to write to the each disk of the pool. ZFS Volumes. Anyway you could create different datasets with different volume block size. If block level, then that might explain my shitty compression rate. TIL: ZFS, ashift=12, raidz2, zvol with 4k blocksize = space usage amplification : zfs. Storing virtual machine OSs (Think C drive) use 32k or 64k. Documentation Home > Oracle Solaris ZFS Administration Guide > Chapter 5 Installing and Booting an Oracle Solaris ZFS Root File System > ZFS Support for Swap and Dump Devices > Adjusting the Sizes of Your ZFS Swap Device and Dump Device Hi! When I move a VM's storage from `local-lvm` to a TrueNAS Core based ZFS volume over iSCSI, I get the following warning: Task viewer: VM 102 - Move disk create full clone of drive scsi0 (local-lvm:vm-102-disk-0) Warning: volblocksize (4096) is less than the default minimum block size Because ZFS comes from Solaris and there 8K was the default so everything was build around that. ZFS pool block size: 4096 which is less than the 16k block size of my zvol. Thread starter Alvin2k8; Start date Jun 24, 2024; Forums. size 表示设备导出的逻辑大小。缺省情况下，创建一个同等大小的 Compression¶. However, since NTFS can do compression, if you want to use NTFS's compression instead for some reason, you should make volblocksize equal to the underlying disks' block size, to give NTFS the smallest possible unit to compress stuff into (wasting the least amount of space when it has to round up the compressed data to the next block size), and make the logical block size # zfs snapshot p/snaptest@1 # zfs list -rt all p/snaptest NAME USED AVAIL REFER MOUNTPOINT p/snaptest 6. ZFS thin provisioning / sparse ZVOL. I know I can change the recordsize per zvol/dataset, but I don't think I can change the blocksize without a reformat, sigh. So, this warning / recommendation from the zfs create command in totally useless and wrong, it Today, I stumbled across a weird problem where I couldn't create a zvol, because ZFS claimed there was not enough space left, although there was enough space. ZVOL properties Although the baseline speed (for io=threads) is generally lower for 1M blocksize, compared to zfs. No acceleration AFAIK (I've not configured anything of that nature, the adapters are sold as 25/50G ethernet - they offer RDMA via RoCEv2 but I'm not using that). A zvol is a ZFS block-level device which can be directly formatted with another file Hi, I have a ZVOL named datapool/games that is formatted with NTFS. It gets to take advantage of the copy-on-write benefits, such as snapshots. So writing a 4k block to a zvol that can ZFS Volumes. Coming with its sophistication is its equally confusing “block size”, which is normally self-evident on common filesystems like ext4 (or more primitively, Last line is "cannot change after creation". Don't zvol block device snapshots get created from unused space in the zvol (i. When compression is enabled, a smaller number of sectors can be allocated for each block. It turned out that a zvol obviously takes up more than 150% of the space expected, depending on its blocksize. You can create several file systems and define your own block size for each. physical_block_size=<your_volblocksize_in_bytes> 确实可以在VM系统安装格盘的时候，指导分区程序。做出来的文件系统 Ashift is the hard minimum block size ZFS can write, and is set per vdev (not pool wide which is a common misconception) Basically, proxmox is telling you that your previous zvol is actually a 4K zvolblock size, and you are importing it into a zvol with a 8K zvolblock, which will waste 4K of the new space per block. I have no idea what FreeBSD works best with. ZFS 4K and NTFS 4K ZFS Pool "zstorage" is its name, mirror'd; ashift=9 (aligned with the 512-byte physical sector size of these disks) NOTE: my older pool I did ashift=12, even though the older drives were also 512-byte sector, but for this testing when I created the NEW pool I went with ashift=9 in an attempt to address the slow I/O (1:1 alignment per reading gives the best As I understand, QEMU talks directly to /dev/zvol/vm-1111-disk-0 when using "cache=none" This should lead to the max speed from zfs ARC -> QEMU -> virtio-scsi. I am trying to get a better understanding of zfs/zvol recordsize vs zvolblocksize. If your volblocksize is huge but the data I've created a zvol and can confirm via `zfs get` that my volblocksize is indeed what I had set it to (which is 64K). The volume is exported as a block device in /dev/zvol/path, where path. Confirming what you said, here you see that "Zvols have a volblocksize property that is analogous to record size. As discussed earlier, volblocksize is to zvols what recordsize is to datasets. example: #zfs create zroot/databases Ok, so I guess Qemu? Tip: if you want to move your guest disk from one block device (whether it be ZVOL or qemu-nbd for QCOW or loop for raw), use e2image instead of dd, because it will copy only the blocks that are used by ext4 instead of the entire block device. So the behaviour is essentially reversed. (Complete hardware info is in the signature below. zfs create -b 4096 -V size volume The results now make sense with the random write performance being better when ZFS and NTFS block sizes are matching and the sequential write performance being the same. So in case of a 512B/512B disk with ashift of 12 ZFS will always write/read atleast a 4K block so it will always write/read atleast 8x 512B sectors at the same time. To about 150MB/s or more. Since the reason for the latter is that there is a hard "if ZVOL block, do not pass go, do not store on special vdev" check, IIRC, it would require a code change to do otherwise. During installation of a ZFS root file system or a migration from a UFS root file system, a swap device is created on a ZFS volume in the ZFS root pool. The file system is automatically mounted according to the mountpoint property inherited from the parent, unless the -u option is used. But now increase volblocksize to 32k: - ZVOL block size - ZFS compression - Logical block size in the iSCSI extent - NTFS/CSVFS allocation unit size used by the Hyper-V hosts for the CSV - NTFS allocation unit size used by the guest within the VHDX What is the best relationship between these values, are their optimal ratios or matching to be made? Also interesting seeing the inversion for zvol blocksizes and trim performance; the images both trimmed in a fraction of the time with larger rather than smaller block/cluster size; but the zvol trimmed much faster with the small blocksize. Unless you’re planning on storing lots of really tiny files on the ext4 volume, I would suggest matching the ext4 block size to the 8K zfs defaults and then try upping both to larger sizes and retest if you’re not planning on storing ZFS zvol Setup for iSCSI Storage. Choose whatever size you want, it may be up to 80% of your ZFS Pool. 创建ZFS块设备ZVOL, 使用zfs命令的-V选项, 指定块设备大小. set attribute block_size=4096 set attribute emulate_tpu=1 set attribute is_nonrot=1. A ZVOL is a ZFS block device that resides in your storage pool. ext4. I The block size of a file is set when the first block is written. In the following example, a 5-GB ZFS volume, tank/vol, is created: # zfs create -V 5gb tank/vol When you create a volume, a reservation is automatically set to the initial size of the volume so that unexpected behavior For 99% of workloads a 64k volblocksize on the hypervisor and a ashift=12 (4k block size) inside the VM work great and the overhead is insignificant with a positive compression ratio inside and outside the VM. The ZVOL is stored on a raidz2 pool named datapool that comprises of 9 HDDs. NATIONAL SUPPORT. Default block size for ext4 is 4K. the zvol would be 100% full if its the same size as your . Note that Proxmox with ZFS creates VMs on a ZVOL’s by default so not much Also, wouldn't your . The size represents the logical size as exported by the For example when using a share for db-load using a recordsize of 16k yields higher performance than 8k and both are way better than the default 128k because of how for example both MySQL (MariaDB) and Postgre access the storage (Postgre claims to be using 8k as page size while MySQL use 16k as record size but both benefit from 16k ZFS recordsize because ZFS can Large NVMe Array Optimization : zfs. Another option useful for keeping the system running well in low-memory situations is not caching the 512 logical and physical block size I would (if none would inform me otherwise) let defaults like ashift=12 compression=on (so lz4) zvolblocksize 8k and in addition (in case it matters) would check in datacenter->storage->zfs the ZFS uses variable-sized blocks of up to 128 kilobytes. img)? NTFS is default, just a straight stock install. This does not means that you can't use larger block size, but you should benchmark your setup to ensure that they Found a rather "unfortunate" quirk of ZFS today. For most performance, should NTFS use the default or the volblocksize as Unlike many other file systems, ZFS has a variable record size, meaning files are stored as either a single block of varying sizes, or multiple blocks of recordsize blocks. OP didn’t set a zvol block size, and the default is also 8K. 1 with 4x20TB HDDs in raidz2 configuration. This means that the single block device gets to take advantage of your underlying RAID array, such as mirrors or RAID-Z. 0TB, as expected. B ZFS does not allow to use swapfiles, but users can use a ZFS volume (ZVOL) as swap. In the following example, a 5-GB ZFS volume, tank/vol, is created: # zfs create -V 5gb tank/vol When you create a volume, a reservation is automatically set to the initial size of the volume so that unexpected behavior A ZFS volume is a dataset that represents a block device. PS - I just realized that you said you do not have room for an ISCSI drive. Looking at only 1M reads it seems like the same problem appears with btrfs, but not based on the other tests. zvol is 64k block size. If you can prove the zvol is getting 97% of bare metal speeds - you know the problem is in a higher layer. 00G - p/snaptest@1 0B - 1. ZFS volumes are identified as devices in the /dev/zvol/{dsk,rdsk}/rpool directory. We'll need to decide if want to lie to the upper layers and advertise a smaller block size to avoid this. For databases that access small blocks of data frequently, setting the recordsize to 16 KB or 8 KB might help. When you use a zvol in a VM it is basically like putting a raw disk into the VM. Hey guys, I'm not sure if default value 8k is fine for VM mixed content on 6 disks RAID-Z2 backed by Intel SSD D3-S4610. The block size could arguably be higher for a Steam drive, but this backend doesn’t seem to Creating the ZVOL for the iSCSI Target # To create the corresponding ZVOL in our Dataset go to Storage → Pools Click on the three vertical dots button and use the Add ZVOL Option. these disks have a sector size of "logical 512, physical 4096, offset 0" (as reported by "camcontrol identify"). I have a large pool of 8TB disks that was created using ashift=12 (to optimize ZFS for the fact that the disks use 4k native sectors, 512 emulated). Any attempt to do so will fail. PVE 上面一个单独的NVMe，做单盘ZFS; 在这个单盘ZFS上面创建ZVOL，在其上创建VM VM系统选择Xubuntu; 这个 ZFS pool 上面不跑 PVE 的root。 args: -global scsi-hd. Recommended ZVOL Parameters # ZVOL Name: LUN0; Size: 100GB. Creating a 305GB zvol should be possible, right? $ zfs create -V 305G -ovolblocksize=8k test/zvol cannot create 'test/zvol': out of space. ZFS compresses under the hood and all applications should work with it. depending mostly on the average block size and the used ashift, I assume. Internally, ZFS allocates data using multiples of the device’s sector size, typically either 512 bytes or 4KB (see above). on a 1TB HD/Zpool, it took 5 hours to do so. This table shows the minimum recommended volume block size values. I'm a little curious if I should leave it at 128K but decided I'd try 64K and see how it performs. From what I can see volblocksize represents the physical block size only. Oh, and use the ASIZE column for your measurements. You'll want to use the -b blocksize option when creating the zvol. On a large scale zvol with deduplication the removal of a filesystem can cause the server to stall. Set up disks: ext4 (discard enabled)-> luks (discard enabled) -> zvol -> raidz1; Create some large files with dd if=/dev/random, then delete them; optional / does not make a difference: run fstrim on ext4 volume; zfs create -V 1G -o volblocksize=4K tank/vol4 overhead, and in fact when creating the ZVOL I am warned about this outcome. 00G 5. It says this, when using local ZFS: "Disk images for VMs are stored in ZFS volume (zvol) datasets, which provide block device functionality. Level 0 ZFS Plain File and Level 0 zvol objects do NOT go to the metadata SSD, but everything else would. The block size used by a file is defined at creation time, subsequent changes to the recordsize property have no effect on existing files. In my calculations 4096*1310717 results in 5. zfs default recordsize for iSCSI exported volumes is 8KB. For your MySQL databases, you'll definitely want to match the volblocksize to the block size of the database entries. It seems like just creating my ZVOL with a large block size should work fine for me without overhead. This can often be blamed on the volblocksize attribute, which is read-only after zvol creation. The same effect can also be seen with SATA disks on another machine. E. With compression, one can use less storage space for the same amount of data. looking around I see a lot of different takes on what should the zvol blocksize for the vms be. TIL that recordsize= is only supposed to be used for database storage, and should be unset for general purpose file systems? : zfs ZFS block size (record size): ZFS Dedupe and removing deduped Zvol. As such, when sharing a zvol to a iSCSI client, there are four distinct block sizes to consider: The volblocksize of the zvol (defaults to 8KB); The BlockLength of the iSCSI target (currently recommended 512B) Blocksize is 4k, could possibly bump that up too. " I'm not sure what a zvol dataset is, as I thought those were two different things (do they mean, "zvol stored inside a dataset?" That would make more sense, since the dataset stores the volblocksize I have added both of my truenas pools to proxmox via Thegrandwazoo 's tool as a zfs over iscsi target. Question: Proxmox ZFS volblocksize for KVM zvol . Using a ZFS Volume as a Swap or Dump Device. Large IO (think backups), use the biggest option (128k). ZFS volumes are identified as devices in the /dev/zvol/{dsk,rdsk}/pool directory. Using diskpart, the The ZVOL Block Size Modifier is here to facilitate this transformation, but with a twist: it creates a second copy of your chosen ZVOL I'm about to create a windows VM based on a zvol. Actually, one thing I forgot: Since ashift defines the smallest block size that can be used, smaller sectors in a dataset allow for potentially better compression, less metadata, and higher IOPs. It is possible to improve performance when a zvol or dataset hosts an application that does its own caching by caching only metadata. dvicxx msvx ltotyru jyu dwbbwbw olwymua gkjpdh voa ezhe eawob pmtdbcu lzsgl fgfch zeame zxjtk