Should I use a CoW filesystem on my PC if I only wanted snapshot capabilities ? Post: 303044797

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Top Forums UNIX for Beginners Questions & Answers Should I use a CoW filesystem on my PC if I only wanted snapshot capabilities ? Post 303044797 by stomp on Wednesday 4th of March 2020 05:42:58 AM

03-04-2020

Registered User

Another comment:

A con against zfs is the inability to remove VDEVs. A VDEV is a subpart of a volume.

Example:

Say you have a data volume consisting of a single disk(=vdev, 1 TB). You decide to replace your vdev of a single disk with a raid-1 vdev(1 TB), since you want add redundancy to be safe in case of a disk crash. That's possible. Over the years, you add another 2 vdevs(2x2TB,2x4TB) with raid-1 arrays. So you then have 3 vdevs making up your volume consisting of 2 disks each with an overall capacity of 7 TB.

You now decide you want to increase your storage again and simultaneously reorganize your 3 x raid1(6 disks=>7 TB usable) to 1 x raidz2(5x6 TB =>18 TB usable) to be able to cope with more simulateous disk crashes(2 disk crashes without data loss here) and at the same time reduce the number of active disks(6->5).

With zfs this is only possible by reformatting, since device removal is not fully supported by now. So you have to copy all the data, which must be done offline. ZFS top level device removal is in development at the moment, but i expect some years to pass until even raidz vdevs can be removed.

With LVM you can just add the new underlying disks and remove the old disks. No problem. All is possible to be done online. Btrfs can do that to and is even flexible to do more advanced migrations.

And Here are some experience reports about btrfs and zfs from users:

ZFS Vs BTRFS : linux

Some not to long gone data loss stories about btrfs are also there. I assume the cause may be lacking knowledge about file system operation. But of course that's only a suspicion.

Last edited by stomp; 03-04-2020 at 06:52 AM..

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LEARN ABOUT DEBIAN

mkfs.btrfs

MKFS.BTRFS(8)						      System Manager's Manual						     MKFS.BTRFS(8)

NAME

       mkfs.btrfs - create an btrfs filesystem

SYNOPSIS

       mkfs.btrfs [ -A alloc-start ] [ -b byte-count ] [  -d data-profile ] [  -l leafsize ] [	-L label ] [  -m metadata profile ] [  -n nodesize
       ] [  -s sectorsize ] [  -h ] [  -V ]  device [  device ... ]

DESCRIPTION

       mkfs.btrfs is used to create an btrfs filesystem (usually in a disk partition, or an array of disk partitions).	device is the special file
       corresponding  to  the  device  (e.g  /dev/sdXX	).   If  multiple   devices  are specified, btrfs is created spanning across the specified
       devices.

OPTIONS

       -A, --alloc-start offset
	      Specify the offset from the start of the device to start the btrfs filesystem. The default value	is  zero,  or  the  start  of  the
	      device.

       -b, --byte-count size
	      Specify the size of the resultant filesystem. If this option is not used, mkfs.btrfs uses all the available storage for the filesys-
	      tem.

       -d, --data type
	      Specify how the data must be spanned across the devices specified. Valid values are raid0, raid1, raid10 or single.

       -l, --leafsize size
	      Specify the leaf size, the least data item in which btrfs stores data. The default value is the page size.

       -L, --label name
	      Specify a label for the filesystem.

       -m, --metadata profile
	      Specify how metadata must be spanned across the devices specified. Valid values are raid0, raid1, raid10 or single.

       -n, --nodesize size
	      Specify the nodesize. By default the value is set to the pagesize.

       -s, --sectorsize size
	      Specify the sectorsize, the minimum block allocation.

       -V, --version
	      Print the mkfs.btrfs version and exit.

AVAILABILITY

       mkfs.btrfs is part of btrfs-progs. Btrfs is currently under heavy development, and not suitable for any uses other  than  benchmarking  and
       review.	Please refer to the btrfs wiki http://btrfs.wiki.kernel.org for further details.

SEE ALSO

       btrfsck(8)

																     MKFS.BTRFS(8)