SOLVED Growing a Pool by Replacing Disks

SlackerDude

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Feb 1, 2014
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I am currently running a TrueNAS server (v12.0-U8.1) with a single storage pool (see full hardware list at the bottom). I am not completely new to TrueNAS, but inexperienced enough in this area to have the following questions.

This RAIDZ2 pool consists of 6 identical WD Red WD40EFRX 4TB drives which have been in service since 2013 (I know, I have more than got my money's worth from these drives). I want to replace these 4TB drives with 10 or 12TB drives, and this thought led me to question the procedure of changing, adding, and removing drives from this pool. Specifically:

1. If I replace all smaller drives successively with bigger ones? Will the overall storage size increase once the last smaller drive is replaced? I found this reference in the FreeNAS v11.3-U5 user guide, which seems to indicate this true (see link below),
https://www.ixsystems.com/documentation/freenas/11.3-U5/storage.html#replacing-disks-to-grow-a-pool

but I have not found anything in the TrueNAS v120-U8.1 documentation that addresses this topic (see link below)
https://www.truenas.com/docs/core/coretutorials/storage/disks/diskreplace/

So I am reaching out to the more knowledgeable among you, to see if this process of replacing disks to grow a pool is still supported.

Thanks in advance!


Case: LIAN LI PC-Q25B
Power Supply: CORSAIR CX430M 430W 80 PLUS BRONZE
Motherboard: ASRock FM2A88X-ITX+
CPU: AMD A6-5400K
CPU Cooler: ZALMAN CNPS8900
RAM: 16GB DDR3
Boot Drive: 2 x SanDisk SDCZ36-016G-B35 16G
Storage Drive: 6 x WD Red WD40EFRX
Intel EXPI9301CTBLK 10/100/1000Mbps
TrueNAS-12.0-U8.1
 

Samuel Tai

Never underestimate your own stupidity
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Yes, this is still supported. I grew my RAIDZ2 pool the same way in TrueNAS 12.
 

SlackerDude

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Yes, this is still supported. I grew my RAIDZ2 pool the same way in TrueNAS 12.
This is encouraging to know. A follow-on question now seems appropriate to ask. Since I have no available SATA ports but do have an available (albeit slower) USB port available, is it reasonable to assume I could attach a USB SATA dock for the purpose of offlining and replacing/drives one at a time?
 

Samuel Tai

Never underestimate your own stupidity
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Unless it's a USB3 port, I wouldn't recommend this, as USB2 would be too slow for the resilvers, and there's a good chance the resilvers would kill the port or the SATA adapter.
 

SlackerDude

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Unless it's a USB3 port, I wouldn't recommend this, as USB2 would be too slow for the resilvers, and there's a good chance the resilvers would kill the port or the SATA adapter.
So, better to utilize only the SATA port by simply downing the drive, swapping it out with the new drive, and initiating the resilver process? I had not considered the possibility of causing a resilver failure due to the speed of the USB interface. Thanks for that!
 

Scharbag

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So, better to utilize only the SATA port by simply downing the drive, swapping it out with the new drive, and initiating the resilver process? I had not considered the possibility of causing a resilver failure due to the speed of the USB interface. Thanks for that!
Yeah, avoid USB connections. SATA or SAS is the way to go for reliability.
 

danb35

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So, better to utilize only the SATA port by simply downing the drive, swapping it out with the new drive, and initiating the resilver process?
Yes, presuming you have sufficient redundancy in your pool. If your pool is RAIDZ1, once you offline a disk, you have no redundancy, and any data error on any other disk will cause a data error in the pool (since ZFS won't be able to fix it). If it's RAIDZ2, you'll still have one disk's worth of redundancy.
 

SlackerDude

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Yes, presuming you have sufficient redundancy in your pool. If your pool is RAIDZ1, once you offline a disk, you have no redundancy, and any data error on any other disk will cause a data error in the pool (since ZFS won't be able to fix it). If it's RAIDZ2, you'll still have one disk's worth of redundancy.
I am in fact using RAIDZ2, as I am a belt & suspenders type of person. :smile: I should receive the new drives today and will begin the process of replacing them one-at-a-time.
 

Chatskiy

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Sep 15, 2020
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I am in fact using RAIDZ2, as I am a belt & suspenders type of person. :smile: I should receive the new drives today and will begin the process of replacing them one-at-a-time.
One other option is to get SATA PCI-E controller or even mSATA to SATA passive adapter ($5 or so) and just hang a new drive off it - it doesn't have to be pretty, but the pool would be healthy throughout.
Although given that you are on RAIDZ2 that's probably not necessary.
 
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