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XFS vs. ZFS - A Non-Too-Tech Conversation


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Hi Guys,

 

I am hoping to start a conversation that does NOT dive too deep into extreme technical details. Something that newbs and experts alike can follow. ZFS is a little bit of a mystery to me (and I have been using unRAID for over 13 years). Since unRAID introduced cache pools, I now have 3 pools and formatted them as ZFS - but nothing beyond that.

 

  • What are the benefits of one vs. another?
  • Is one more beneficial to Cache pools as opposed to array drives?
  • Any decent tutorials? I know SpaceInvader is a big ZFS fan, and has awesome explaining videos.
  • In a nutshell, what are snapshots? Do they require a lot of additional drive space?
  • Are ZFS snapshots a better alternative to regular appdata backups?
  • What is the learning curve on snapshots (I know next to nothing about them)?
  • Is this a big-deal conversation? Just format it and forget about it - not worth the learning curve? Or is it?

 

The above are some questions to consider. Please feel free to add and provide some thoughts...

 

I'm sure there are tidbits on this topic around; feel to reference here. 

 

Thank you.

 

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1 hour ago, hernandito said:
  • What are the benefits of one vs. another?
  • Is one more beneficial to Cache pools as opposed to array drives?

Is this only about ZFS vs XFS (BTRFS excluded)? If thats the case then one of the answers is to the above is multi-drive pools vs single drive pools.

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thanks,

1 hour ago, primeval_god said:

Is this only about ZFS vs XFS (BTRFS excluded)? If thats the case then one of the answers is to the above is multi-drive pools vs single drive pools.

 

Great point...I am going to try to track all the responses and summarize at some point. I was excluding BTRFS... because I forgot about it 🙃

 

+1 Advantage for ZFS for cache pools; allows multiple drives in the pool.

 

Thanks.

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ZFS snapshots take less space because they only store the deltas

ZFS replication will be faster since it only sends the deltas

The corollary is that deleting file won't save any space until all snapshots are also deleted

ZFS replication of app data/cache drive doesn't require shutting down and restarting dockers.

ZFS doesn't have a built in file repair system

ZFS can detect bit-rot but can only repair bit-rot in a pool with redundancy(mirror/raidz, etc)

ZFS Master plugin seems to spin up and write to drives often. 

Edited by foo_fighter
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Thank you @foo_fighter.

 

Posting link for SpaceInvader on ZFS Snapshots. I have to watch it again, to refresh my memory.

 

In reading the above, can we surmise:

1 hour ago, foo_fighter said:

ZFS snapshots take less space because they only store the deltas

ZFS replication will be faster since it only sends the deltas

Sounds interesting, specially for cache pools... Question, what happens with files that are stored on cache drive and are then, via mover, moved to array?  With snapshots, does the entire drive get snapshot? Or can you pick individual folders? I really need to watch the video linked above....

 

14 hours ago, foo_fighter said:

The corollary is that deleting file won't save any space until all snapshots are also deleted

Sounds like ZFS or snapshots are not really for array drives (filled with media files).

 

14 hours ago, foo_fighter said:

ZFS doesn't have a built in file repair system

I have had to use XFS Repair dozens of times to fix issues w/ HDDs. Again sounds like ZFS is not really for array drives.

 

14 hours ago, foo_fighter said:

ZFS Master plugin seems to spin up and write to drives often. 

Does it spin the array drives if XFS is only used on cache pools?

 

Thanks again,

 

H.

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18 hours ago, hernandito said:

I was excluding BTRFS... because I forgot about it 🙃

The main reason I asked is because, generally speaking, BTRFS and ZFS offer a lot of the same advantages. Both allow multi-disk pools, both have data integrity features, both have snapshots, both offer a delta based method of sending snapshots from one fs to another. 

ZFS pools can apparently offer faster speeds at the expense of more resources. ZFS pools are less flexible in their layout and in terms of expanding them, BTRFS is more flexible (though not as much as the unRAID array) but lacks a stable raid5 or raid6 option. In the wider linux community ZFS is considered more stable than BTRFS (opinions vary on the stability of BTRFS), but in unRAID BTRFS has been integrated for longer. 

Edited by primeval_god
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4 hours ago, hernandito said:

Thank you @foo_fighter.

 

Posting link for SpaceInvader on ZFS Snapshots. I have to watch it again, to refresh my memory.

 

In reading the above, can we surmise:

Sounds interesting, specially for cache pools... Question, what happens with files that are stored on cache drive and are then, via mover, moved to array?  With snapshots, does the entire drive get snapshot? Or can you pick individual folders? I really need to watch the video linked above....

With Mover, they are treated as normal files, only the primary, most recent non-snapshotted files are moved over into the array.

With Syncoid/Sanoid you can choose individual datasets and sub datasets.

 

4 hours ago, hernandito said:

Sounds like ZFS or snapshots are not really for array drives (filled with media files).

It can be used in the array. For example, I have my cache drive as ZFS and converted 1 array drive to ZFS so I could use it as a replication target.(ZFS->ZFS) The other drives in my array are XFS. I have my app data(dockers and docker data living on cache) replicated over to the ZFS drive for backups.

 

4 hours ago, hernandito said:

I have had to use XFS Repair dozens of times to fix issues w/ HDDs. Again sounds like ZFS is not really for array drives.

It can be. RAID is not backup, so for catastrophic cases(any filesystem) that would be the recovery mechanism.

 

4 hours ago, hernandito said:

 

Does it spin the array drives if XFS is only used on cache pools?

I was only referring to the ZFS_Master plugin spinning up ZFS drives. It didn't touch any of my XFS drives. I actually set the plugin to manual refresh and it seems to have stopped the spinning up and writing.

 

4 hours ago, hernandito said:

 

Thanks again,

 

H.

 

  • Thanks 1
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