[TriLUG] Help on disk managment: LVM vs. ZFS

[Ron Kelley via TriLUG]

I think the answer depends on why your existing filesystem is not fulfilling your needs.  In other words, what do you want to get out of ZFS that can’t be delivered by LVM?

Keep in mind, while ZFS is decent, it takes lots of RAM to do the fancy stuff like de-duplication.  I personally tried ZFS on Linux (ZoL) a year back and had terrible speeds (initial config was good but the speed started to deteriorate after a while).

Ultimately, I switched to BTRFS to get snapshots, compression, logical volumes, etc.  De-duplication was not part of my requirements.  Happpily running BTRFS on a number of production servers; no problems whatsoever. 


My $0.02


-Ron






On May 24, 2017, at 11:52 AM, mr-trilug via TriLUG <trilug at trilug.org> wrote:

My system:
   Ubuntu 16.04
   LXDE installed

   HD.1    750 GB as LVM with root, home, swap sections, in Samsung RV515 laptop

       and for backup and additional storage:
   HD.2    320 GB, 4 partitions
       or    --- one at a time goes in external HD case
   HD.3    120 GB LVM with 2 sections (but not yet recognized or mountable.

Q1: Would I benefit from installing ZFS to use instead of LVM?

"ZFS is a combinedfile system <https://en.wikipedia.org/wiki/File_system>andlogical volume manager <https://en.wikipedia.org/wiki/Logical_volume_management> "Zettabyte File System"     ZFS does away with partitioning, EVMS, LVM, MD, etc. The available disks (of any size) are used to the best of their ability. Compression can be used to increase bandwidth. (q.v. Reiser 4, and cloop?)"
cf.: https://wiki.ubuntu.com/ZFS

Q2: How to progress from status, below, to a mountable status (pv and vg exist but lv does not)

fdisk outpu:

Disk /dev/sdb: 110.4 GiB, 118526284800 bytes, 231496650 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0xd389a7da

Device     Boot     Start       End   Sectors  Size Id Type
/dev/sdb1            2048 115000000 114997953 54.9G 8e Linux LVM
/dev/sdb2       115001344 231496649 116495306 55.6G 8e Linux LVM


lvm output

--- Physical volume ---
 PV Name               /dev/sdb1
 VG Name               120g-vg
 PV Size               54.84 GiB / not usable 3.34 MiB
 Allocatable           yes
 PE Size               4.00 MiB
 Total PE              14037
 Free PE               14037
 Allocated PE          0
 PV UUID               1xzJUw-vhbS-kLMc-IjtT-bLtm-WeqM-NFH4Ty

 --- Physical volume ---
 PV Name               /dev/sdb2
 VG Name               120g-vg
 PV Size               55.55 GiB / not usable 2.47 MiB
 Allocatable           yes
 PE Size               4.00 MiB
 Total PE              14220
 Free PE               14220
 Allocated PE          0
 PV UUID               fN0ide-WeXH-uJex-z4nQ-nyUo-ZSeK-VfrIJw


--- Volume group ---
 VG Name               120g-vg
 System ID
 Format                lvm2
 Metadata Areas        2
 Metadata Sequence No  1
 VG Access             read/write
 VG Status             resizable
 MAX LV                0
 Cur LV                0
 Open LV               0
 Max PV                0
 Cur PV                2
 Act PV                2
 VG Size               110.38 GiB
 PE Size               4.00 MiB
 Total PE              28257
 Alloc PE / Size       0 / 0
 Free  PE / Size       28257 / 110.38 GiB
 VG UUID               7b1yjA-MW9S-zcwX-e8MO-y7BP-YCPs-HGDqlP

===============
Michael Rulison
  919 205 9168 (mobile phone)
  3256 LEWIS FARM RD, RALEIGH  NC 27607-6723

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