New System with different hdd disk size - Which raid type should i use?

[teqqyde]

Hello,
i just bought a new system to migrate from my old two synology nas systems to a new freenas. One of the advantages of synology where the SHR, so you can mix different sizes of disks in one pool.

Not i have
2 x 4 TB Seagate Ironwolf
4 x 3 TB Seagate (dont not the type)
2 x 2 TB WD Red

Yesterday i tried to google the best practises to create a pool with similar kind of disks, but i did not found a good anwser. As far as i understood i have two acceptable versions:

1. different mirrored vdevs
I Create four mirrored vdevs with the same size of disks and combine them into one pool. Problem: The FreeNAS Storage Guide (i installed freenas in a test vm) told me, that i should not mix different vdev sizes...

2. One RaidZ2 vdev
The other way where be to create one RaidZ2 vdev. Now the pool size would be dramatically smaller then with the other possibility. But with that the chance to have a complete failure of my hole pool is smaller (of course i have a backup!)

To buy new disk is not possible at the moment. But i will replace the 2 TB disk in the next few month, because they aren't the newest anymore.

I hope you can give me a good recommendation which type of pool i should use. Thank you.

 

[garm]

First of all you need to burn in the drives.

Second, you can play around with pool layout in this calculator https://www.wintelguy.com/zfs-calc.pl

What you need to consider is the future storage need. Even if it costs you some net storage right now it’s easier not to have to rebuild the pool later.

Increase in vdev count gives you increases IOPS. Larger vdevs give you better net storage.

With an 8 drive system I would not go for 4 mirror vdevs as you probably won’t have need to the IOPS and that would give you a net storage quota of less then 40% raw storage.

A single RAIDZ2 will give you a net storage quota of 65% but the IOPS of a single drive. (And the pool will consider all drives to be the size of the smallest drive)

For a home setup one or two vdevs should be enough given 1GbE network and nothing fancy like ISCSI.

 

[teqqyde]

Thank you for your recommendations.

That i cannot migrate my disks directly to freenas was allready clear. But thanks for the advice.

At first time i thought i would use this system also for a proxmox shared storage, but i dont want to do this anymore. So it will be just a network share for two persons and plex (transcoding on other system). I will play arount with the calc and see what i will get.

 

[sretalla]

If you take the RAIDZ2 option and upgrade the 2TB disks to 4TB, you will see an increase in pool capacity... then if you replaced the 3TB with 4TB, the capacity should increase again.

Clearly that means that in the initial phase, you can't get to all of your raw storage capacity (it seems you understood that well though).

 

[teqqyde]

yes i know. but thanks for clarity.

I opened this thread because i like to know which of both ways are the less bad ones. :) But it seems i got my anwser. Thank you.

 

[pschatz100]

Hello,
i just bought a new system to migrate from my old two synology nas systems to a new freenas. One of the advantages of synology where the SHR, so you can mix different sizes of disks in one pool.

Not i have
2 x 4 TB Seagate Ironwolf
4 x 3 TB Seagate (don't not the type)
2 x 2 TB WD Red

Yesterday i tried to google the best practises to create a pool with similar kind of disks, but i did not found a good anwser. As far as i understood i have two acceptable versions:

1. different mirrored vdevs
I Create four mirrored vdevs with the same size of disks and combine them into one pool. Problem: The FreeNAS Storage Guide (i installed freenas in a test vm) told me, that i should not mix different vdev sizes...

2. One RaidZ2 vdev
The other way where be to create one RaidZ2 vdev. Now the pool size would be dramatically smaller then with the other possibility. But with that the chance to have a complete failure of my hole pool is smaller (of course i have a backup!)

To buy new disk is not possible at the moment. But i will replace the 2 TB disk in the next few month, because they aren't the newest any more.

I hope you can give me a good recommendation which type of pool i should use. Thank you.

You didn't say what your priorities are: redundancy versus performance, or how much storage space you need in the near term. There are several ways you could configure storage that will make sense.

Personally, I like RaidZ2 because I prefer two disks of redundancy when working with disks larger than 2TB. However mirrors yield greater performance.

At the end of the day, there is no requirement for all the disks to be configured into one large pool.

1) You could create two four-disk RaidZ2 pools: 2x4TB +2x2TB, and 4x3TB. This would give you 10TB raw capabity and approximately 7TB usable storage (assuming 80% of formatted capacity.) After upgrading the 2TB disks to 4TB (or greater), your raw capacity would be 14TB yielding approximately 10TB of usable storage.

2) You could create two pools: one six disk RaidZ2 of 2x2TB + 4x3TB, plus one mirror of 2x4TB. This would give you 12TB raw capacity yielding about 8.5TB usable. After upgrading the 2TB disks to 3TB you would have 16TB raw capacity (approx 11.5TB usable.)

3) Two pools: one six disk RaidZ2 of 2x4TB + 4x3TB, plus one mirror of 2x2TB. This would give you 14TB raw capacity to start with, about 10TB usable. You could upgrade the 2TB disks for additional capacity at will.

Option 1 gives you the smallest capacity but also the most redundancy - a safe and reliable setup.
Option 3 gives you the most capacity and with reasonable redundancy. Depending upon your storage needs, you may not need to use the 2TB drives at all.

I would probably follow Option #3.

 

[Heracles]

Hi Teqqyde,

I would also go with the single RaidZ-2 vDev and rely on auto-expand to increase the capacity. Once the vDev and pool are created, you are free to replace the drives as you need.

2x 2TB
4x 3TB
2x 4TB

According to how big a pool you wish, you replace the 2TB first, the 3 TB next and if required, the 4 TB.

Should you replace all of them with say 10 TB drives, your pool would go from
6x 2TB = 12
To
6x 3TB = 18 after replacing 2 drives
To
6x 4TB = 24 after replacing 6 drives
To
6x 10TB = 60 after replacing all 8 drives

Doing it slowly will allow you to put drives manufactured at different moment, so a reduced risk to have all of them failing at once. It will also give you the time you need to test each drive on arrival before putting them in the server.

Always try to keep your pool below 50% of its capacity and factor in the snapshots, new data, new usage and more in your planning.

Have fun designing your system,