Expanding Capacity via extra drives

Pabs

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Jan 18, 2017
Messages
52
Hi,

In a QNAP I am able to add more drives to an existing Array and then just expand the Array's capacity.

To confirm, is this not supported within FreeNAS/ZFS?

Asking as I started with a 4 Bay server, now have an 8 Bay one and would love to start using my remaining Bays and so far haven't been able to find a straight answer other than creating another pool and putting disks over there and what not...

Thanks,
 

blueether

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Aug 6, 2018
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Last edited:
Joined
Oct 18, 2018
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Asking as I started with a 4 Bay server, now have an 8 Bay one and would love to start using my remaining Bays and so far haven't been able to find a straight answer other than creating another pool and putting disks over there and what not...
Hi @Pabs. Check out the User Guide for Extending a Pool by either resilvering each drive in a vdev with a larger drive or adding a vdev to a pool.

EDIT: Or read the post above by @blueether. I let my browser go stale and missed the reply above.
 
Joined
Oct 18, 2018
Messages
969
@Pabs I think either you are misunderstanding us or we are not understanding your issue. You are correct, you cannot expand a vdev once made. But you CAN extend a pool.

For example, if you start as follows
Code:
pool1
  raidz1-0
    disk0
    disk1
    disk2
    disk3


You can stripe another vdev as follows

Code:
pool1
  raidz1-0
    disk0
    disk1
    disk2
    disk3
  raidz1-1
    disk4
    disk5
    disk6
    disk7


I believe the User Guide covers this some place.
 

Pabs

Explorer
Joined
Jan 18, 2017
Messages
52
@Pabs I think either you are misunderstanding us or we are not understanding your issue. You are correct, you cannot expand a vdev once made. But you CAN extend a pool.

For example, if you start as follows
Code:
pool1
  raidz1-0
    disk0
    disk1
    disk2
    disk3


You can stripe another vdev as follows

Code:
pool1
  raidz1-0
    disk0
    disk1
    disk2
    disk3
  raidz1-1
    disk4
    disk5
    disk6
    disk7


I believe the User Guide covers this some place.

Thanks, if I stripe it wouldnt it then be like a RAID0 and if one of the vdevs fail, would it take the whole pool down?
Maybe it's a silly question, can vdevs fail?

Thanks,
 

colmconn

Contributor
Joined
Jul 28, 2015
Messages
174
If one of your vdevs fail you'd loose the entire pool. Vdevs being made of drives fail when you loose more than the level of redundancy provided by an vdev. In your case with RAIDZ1 you'd need to loose two drives in one vdev for the vdev to fail.
 
Joined
Oct 18, 2018
Messages
969
Thanks, if I stripe it wouldnt it then be like a RAID0 and if one of the vdevs fail, would it take the whole pool down?
Maybe it's a silly question, can vdevs fail?
Yes, vdevs can fail because, as @colmconn said, they are made of disks. RAID0 is most like 1 pool with 2 vdevs and each vdev contains 1 drive. ZFS is quite different than traditional raid though; even when they seem very similar.

Do keep in mind that using zfs and redundant vdevs does not replace a backup. Any data you really cannot live without you should keep at least one backup.
 

Pabs

Explorer
Joined
Jan 18, 2017
Messages
52
Yes, vdevs can fail because, as @colmconn said, they are made of disks. RAID0 is most like 1 pool with 2 vdevs and each vdev contains 1 drive. ZFS is quite different than traditional raid though; even when they seem very similar.

Do keep in mind that using zfs and redundant vdevs does not replace a backup. Any data you really cannot live without you should keep at least one backup.
yes, do back it up to my old QNAP
 

sretalla

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Jan 1, 2016
Messages
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Just to help you to read what the forum is telling you... It's not recommended generally to run large drives in RAIDZ1 due to concerns about long resilvering in the case of one drive failure and being without fault tolerance during that resilver process (losing a second one during that and your whole pool is dead).

Having said that, you're already taking that risk today, and if you understand it and are OK with it, no problem to effectively duplicate that in a second VDEV... with the further understanding that it's an "all eggs in one basket" story.

You seem to have understood the concept of a separate backup and that, together with a clear understanding and acceptance of the risks you'll be taking possibly make it OK to go ahead with what you initially asked about. It's really up to you.
 
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