Add a drive to existing vdev

hammer8

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May 18, 2019
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Hi, I’m trying out FressNAS for the first time since it’s so neat to be able to run it as a vm and do away with my Areca RAID cards. However, I can’t seem to find a way to add a new hard drive to an existing vdev; something like RAID expansion that’s available on Areca RAiD cards and ReadyNAS devices (the other storage system I’ve used). I’ve tried searching, and it seems I can add vdevs to an existing pool, but I can’t seem to find a way to add new disks one at a time to increase storage capacity. Maybe I just don’t have the terminology correct, but basically, I have a 5 x 4 TB RAIDz2 vdev and I have created a pool with it, now, I would like add a new disk to make it 6 x 4 TB. This will allow me to not “waste” additional disks for redundancy. Thank you.
 

styno

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Apr 11, 2016
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ZFS allows you to add an additional vdev, it doesn't allow you to grow an existing vdev.
This means that if you add a single disk, you will expand your RAIDz2 vdev with a vdev containing the single disk. In creating a stripe like this you will essentially throwing away the redundancy of your pool.
Here is the section of the docs that covers this -> https://www.ixsystems.com/documentation/freenas/11.2-U4.1/storage.html#extending-a-pool
 

hammer8

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Thank you...is that a feature that’s being developed? In my search, I found a thread which seems to suggest it’s an upcoming feature, but that was back in 2015.
 

anmnz

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samyboy

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But this also means that I can not invest small amount in say 4 disks with Raidz2 initially and as my needs grow keep adding the disks. Essentially I have to put all disk-money up front to get best results.. like 8 disk in Raidz2.. Somehow difficult for me to diagest it.

( As you can guess I am totally toally new to FreeNAS and come from Synology world. Wanting not to purchase Synos but build my own FreeNAS ). Is there a way to achieve slow growth?
 

styno

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Not entirely true. While you have to do some upfront planning before using a zfs based solution you are able to expand your pool. The only downside is that you have to expand it in a way that the redundancy is not lost. If you for example start with 6 drives in raidz2, you would likely expand with another 6 drives in raidz2. Or you start with a single mirror and add mirrored vdevs to the pool when you need more capacity/performance.
 

samyboy

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Thanks for your reply Styno.. but approach above does add lot of inefficiency. 6 with disk in Raidz2 will have 2 parity.. and adding another 6 will put 2 more in Parity.. ideally out of 12 disks - I would love to have total 2 in parity not 4.. Did I get this right or am I missing the point? I am in country where disks are super expensive.. I mean super expensive.
 

Chris Moore

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Thanks for your reply Styno.. but approach above does add lot of inefficiency. 6 with disk in Raidz2 will have 2 parity.. and adding another 6 will put 2 more in Parity.. ideally out of 12 disks - I would love to have total 2 in parity not 4.. Did I get this right or am I missing the point? I am in country where disks are super expensive.. I mean super expensive.
More vdevs gives you more IOPS, so there are advantages. I did that. I have two vdevs of six drives each, with each vdev being RAIDz2. Yes, there are four disks worth of space (roughly) dedicated to parity, but that makes my data even safer, which is what ZFS is all about.
Being able to expand a RAIDz2 vdev by simply adding additional drives, which appears to be what you want, is still more than a year away because the development team is focused on other tasks currently.
 

Chris Moore

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FressNAS for the first time since it’s so neat to be able to run it as a vm
If you are going to run FreeNAS as a VM, there are some things you need to do, or you risk loosing all your data. We have seen it happen time and time again. Please read the guides thoroughly before putting data in a virtaul instance of FreeNAS:

"Absolutely must virtualize FreeNAS!" ... a guide to not completely losing your data.
https://www.ixsystems.com/community...ide-to-not-completely-losing-your-data.12714/

Virtually FreeNAS ... an alternative for those seeking virtualization
https://www.ixsystems.com/community...ative-for-those-seeking-virtualization.26095/

FreeNAS 9.10 on VMware ESXi 6.0 Guide
https://b3n.org/freenas-9-3-on-vmware-esxi-6-0-guide/

Also very useful:

Slideshow explaining VDev, zpool, ZIL and L2ARC
https://www.ixsystems.com/community...ning-vdev-zpool-zil-and-l2arc-for-noobs.7775/

Overview of ZFS Pools in FreeNAS from the iXsystems blog:
https://www.ixsystems.com/blog/zfs-pools-in-freenas/

Terminology and Abbreviations Primer
https://www.ixsystems.com/community/threads/terminology-and-abbreviations-primer.28174/
 

samyboy

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Dec 11, 2019
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More vdevs gives you more IOPS, so there are advantages. I did that. I have two vdevs of six drives each, with each vdev being RAIDz2. Yes, there are four disks worth of space (roughly) dedicated to parity, but that makes my data even safer, which is what ZFS is all about.
Being able to expand a RAIDz2 vdev by simply adding additional drives, which appears to be what you want, is still more than a year away because the development team is focused on other tasks currently.

Point taken Chris.. need to to save a bit more before I pull the trigger. Many thanks for your reply.
 
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