Freenas advise please: RAID array ? vdev ? what are my options ?

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DrStein99

If it does not exist ? I am probably building it.
Feb 3, 2018
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New Jersey, USA
I have a NAS (freenas) server, bank of 6 drives in a raid-5 array. I have to expand the size of the array. In order to do that, I have to offload the data - then break the array to add drives to it, then copy the data back. Not a big deal of course, just somewhat inconvenient.

I do not know all the options of Freenas, I know they probably made some updates into data handling between the vdev or zvol or how to go about building a stable storage bank.

My question is;

Should I rebuild the raid-5 array to add the drives? Is there another type of array with the same safety as raid-5 with option for me to add drives to expand in the future without having to offload all the existing data?
 

ttabbal

Active Member
Mar 10, 2016
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There has been talk about in-place upgrades, but I don't think anything has come of it. It's a difficult problem and it's very high risk.

You can make a striped mirror raid-10 style array. You can upgrade those 2 drives at a time. Downside is 50% usable space.

You can make another raidz and add it to the pool. Downside is you need a full set of drives to add all at once. It also leaves the array unbalanced, which doesn't hurt anything, just lowers max performance.

You can upgrade each drive one at a time. Takes forever, but it does maintain uptime. And you still need a full replacement set all at once.

Other than that, you break it and re-build.

Depending on the individual disk size, you might want to consider raidz2. Once drives get big enough, the rebuild time leaves you open to a second failure. There are lots of detailed articles out there about it, but at the end of the day it's your data and you have to decide how much risk you can tolerate.
 

DrStein99

If it does not exist ? I am probably building it.
Feb 3, 2018
115
4
18
50
New Jersey, USA
I have 450gb sas 10k rpm drives. (5) in the array + (1) hot spare. I will be adding (2) drives to the array, give me (7) total with (1) hot spare.

raidz2 ? I will read about this thank you.
 

kapone

Well-Known Member
May 23, 2015
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The above are all the reasons, I don't run ZFS at home. Actually I don't run it for my business either. I find it too limiting, not very performant, and I'm exchanging one set of issues (raid cards etc etc) for another (software bugs, more hardware needed, difficult HA setups etc).

I'm STILL running plain-jane HW raid cards, raid arrays, windows (not that, that matters) and NTFS. Critical things are replicated in realtime, with a tiered backup strategy. This is for my business and hasn't failed me for over 15 years.
 

Ray

Member
Apr 24, 2016
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If you continue to add Vdevs then you never have to break the pool and reload. IOW, you can add another Vdev of 5 drives and hot spare without affecting the current data. This is true for TrueNas Core 12 which is what FreeNas has morphed into. As mentioned, another option would be to add larger drives one at a time and resilver them each. Once all the drives have been replaced the larger total will automagically appear. This would give you another Vdev worth of drives you could add as needed in the future.

I also agree that if yo do rebuild then going to raidZ2 is a better way to go.