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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
Old 03-04-2020
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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vxpfto(1M)																vxpfto(1M)

NAME
vxpfto - set Powerfail Timeout (pfto) SYNOPSIS
vxpfto -g diskgroup -t timeout vxpfto [-g diskgroup] -t timeout volume_list vxpfto [-g diskgroup] -o pftostate={enabled|disabled} vxpfto [-g diskgroup] -o pftostate={enabled|disabled} volume_list DESCRIPTION
Powerfail Timeout is an attribute of a SCSI disk connected to an HP-UX host (see the pfto(7) man page). The vxpfto command sets the Power- fail Timeout interval on a set of Volume Manager disks, either all disks in a disk group, or all disks underlying the volumes listed. The first form of the command sets the same PFTO value for all the disks in the specified VxVM diskgroup. In the second form, all disks underlying the given list of volumes are selected, optionally restricted by the disk group specified with the -g option. If you specify a diskgroup, any volume in the list not belonging to the diskgroup is ignored. Use the -o pftostate option to disable or enable PFTO. By default, PFTO is enabled. You can enable PFTO either on all disks in a disk group, or on all disks underlying the volumes listed. If you invoke vxpfto without arguments, it displays a usage message. OPTIONS
-g diskgroup Specifies the disk group for the operation, either by disk group ID or by disk group name. -o pftostate={enabled|disabled} Enables or disables the use of PFTO for IO. -t timeout Specifies the PFTO value in seconds. The value must be zero or a positive integer. Zero represents the system default PFTO value. The default value depends on the disk driver controlling the disk device. volume_list A list of VxVM volume names. List items must be separated by white-space. EXIT CODES
vxpfto returns a zero if successful. If it encounters an error, vxpfto exits and displays a message on standard error. Defined exit codes are: 0 Success. 1 No PFTO value specified. 2 No diskgroup or volume list specified. 3 Illegal PFTO value specified. EXAMPLES
Set the PFTO value on all disks in disk group testdg to 100 seconds: vxpfto -t 100 -g testdg Set the PFTO value to 50 seconds on all disks underlying volume01 and volume02 in disk group testdg: vxpfto -t 50 -g testdg volume01 volume02 Set the PFTO value to 300 seconds on all disks underlying volume01 and volume02, even though they are not in the same disk group: vxpfto -t 300 volume01 volume02 Disable PFTO on all disks in disk group testdg: vxpfto -g testdg -o pftostate=disabled Enable PFTO on all disks underlying volume01 and volume02i in disk group testdg: vxpfto -g testdg -o pftostate=enabled volume01 volume02 SEE ALSO
vxdisk(1M), pfto(7) VxVM 5.0.31.1 24 Mar 2008 vxpfto(1M)
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