Reply
Highlighted
Aspirant
Aspirant

Mixing drive makes/models within a NAS

firmware 6.7.4

readynas 2120

 

I have my nas configured as a raid 5 (4 disk, 2tb/disk).

 

I need to expand my storage capacity. I was going to put in 4tb hard drives. My plan was to pull out 1 of 2tb disks, replace it with the a 4tb, wait for the NAS to sync and then repeat the process with the other 3 disks. As I understand it, once the last disk is installed and synced then and only then will my storage capacity increase, correct?

 

2nd question, I see that this has been asked before, but I wanted to ask again.

 

I currently have 1----4tb hard drive, Seagate 5900rpm 4TB NAS HDD SATA 64MB Cache 3.5-Inch Internal Bare Drive (ST4000VN000)

 

Would it be a problem to get 3 more drives that were different brands, but same capacity?

 

I was looking at either the Seagate 5900 4TB IronWolf NAS SATA 6Gb/s NCQ 64MB Cache 3.5-Inch Internal Hard Drive (ST4000VN008

 

Or

WD Red 4TB NAS Hard Disk Drive - 5400 RPM Class SATA 6 Gb/s 64MB Cache 3.5 Inch - WD40EFRX

 

 

 

Model: ReadyNAS RND2120|ReadyNAS Duo
Message 1 of 17
Highlighted
Guru

Re: Mixing drive makes/models within a NAS


@FG wrote:

 

As I understand it, once the last disk is installed and synced then and only then will my storage capacity increase, correct? 


No.  That's true with OS 4.1 NAS.  But with your RAID mode on OS 6, you will see expansion when the second disk is added.  The expansion will happen after the volume is resynced, and you might be prompted to reboot before it begins.


@FG wrote:

 

Would it be a problem to get 3 more drives that were different brands, but same capacity?

 

 


It's not a problem, and both the IronWolf and the WD Reds are reasonable choices for the NAS.

 

Some people like mix-and-match, under the theory that it might be more robust.  I haven't seen any real data on that, and I'm not mixing/matching myself.  But I don't see any harm in it either.

Message 2 of 17
Highlighted
Aspirant
Aspirant

Re: Mixing drive makes/models within a NAS

Thank you for your feed back on mix and match!

 

 

I just pulled the existing/current disk (smaller 2tb) 4 (far right bay) from NAS and dropped in the new 4tb. At this point X-RAID is OFF, I have a raid 5 configuration.

 

I went to NAS GUI, under volumes tab I had my existing volume and a additional/new volume called New Volume. When I clicked on NEW VOLUME I had options to Destory or balance. I thought I was going to see an option that would say something........add to existing volume....or something like that. I then turned X-RAID on and the NAS added the NEW VOLUME to the existing volume and started resyncing the data.

 

Does this all sound correct so far, the normal process when expanding storage capacity when using RAID 5 ?

 

Thank you for your help!

 

 

Message 3 of 17
Highlighted
Guru

Re: Mixing drive makes/models within a NAS

It didn't expand initially because XRAID was off.

 

This sounds normal so far.

Message 4 of 17
Highlighted
Aspirant
Aspirant

Re: Mixing drive makes/models within a NAS

Once sync is completed I should be able to turn X-RAID off and keep my raid 5 config, correct?

 

Sorry for all the amateur hour questions, but I would rather not mess this up. There is a lot of data on NAS, which is backed up, but I would rather not get to the point where I need to restore data.

 

Thanks!

 

 

Message 5 of 17
Highlighted
Guru

Re: Mixing drive makes/models within a NAS

You should leave XRAID on, and that will also keep your RAID-5 config.  XRAID uses standard linux RAID modes, so it isn't really proprietary.

 

FWIW, when the second disk is upgraded you will have a multi-layer volume that has a 4x2TB RAID-5 base, and a 2x2TB RAID-1 upper layer (added on the 2 4TB disks).  When you upgrade the third disk, the upper layer becomes 3x2TB RAID-5, and when you add the fourth it becomes 4x2TB.  The upper layer never disappears.

 

It always looks like a single volume to you.

 

 

 

 

Message 6 of 17
Aspirant
Aspirant

Re: Mixing drive makes/models within a NAS


@StephenB wrote:

FWIW, when the second disk is upgraded you will have a multi-layer volume that has a 4x2TB RAID-5 base, and a 2x2TB RAID-1 upper layer (added on the 2 4TB disks).  When you upgrade the third disk, the upper layer becomes 3x2TB RAID-5, and when you add the fourth it becomes 4x2TB.  The upper layer never disappears.

 

Not sure I follow, is that good or bad or neither?

 

 

 

 


 

Message 7 of 17
Highlighted
Guru

Re: Mixing drive makes/models within a NAS


@FG wrote:

 

Not sure I follow, is that good or bad or neither?

 


Neither, it's just true.

 

Here's a shorter version:  Default XRAID gives you the same protection benefits as RAID-5 - and it works with mixed disk sizes (which RAID-5 doesn't do). So just leave it on.

Message 8 of 17
Highlighted
Aspirant
Aspirant

Re: Mixing drive makes/models within a NAS

If you have mixes disk sizes how does the redundancy work?

 

If the disks are all sames I understand how it works, but if you have 3---2tb and 1---4tb then how can redundancy be spread equally across the 4 disks?

 

 

 

RAID 5. This RAID level also provides data redundancy, but it requires at least three disks. RAID 5 uses

the capacity of one disk to protect you from data loss if one disk fails.Your data is distributed across

multiple disks to improve disk performance. The total capacity of your storage system equals the capacity

of all your disks minus the capacity of one disk. It is supported on systems with at least four drive bays.

 

X-RAID uses the capacity of one disk for data storage and reserves the capacity of a second disk for data

protection, which allows the volume to recreate data if a disk fails. In a two-disk system, the usable storage

space is one disk. In a three-disk system, the usable storage space is two disks. In general, the total capacity

of your storage system equals the capacity of all your disks minus the capacity of one disk.

 

Message 9 of 17
Highlighted
Guru

Re: Mixing drive makes/models within a NAS


@FG wrote:

If you have mixes disk sizes how does the redundancy work?

 

 


That's the reply you didn't understand.

 

You can think of it as a layer cake.  For example, imagine you have a 6 disk array, with 1 TB + 4 TB + 6 TB + 6 TB + 4 TB + 1 TB.  You can visualize this as

 

        XXX XXX          top 2 TB layer (drives 3,4)

    YYY YYY YYY YYY      middle 3 TB layer (drives 2-5)

ZZZ ZZZ ZZZ ZZZ ZZZ ZZZ  bottom 1 TB layer (drives 1-6)

 1   2   3   4   4   6  (disk drive number)

 

 

The XXX, YYY and ZZZs are all partitions, laid out as shown in the figure above.  ZZZ is on all the disks; YYY and ZZZ on the 4 TB disks; XXX,YYY, and ZZZ are on the 6 TB disks.

 

 

RAID protection is applied to each layer separately as shown below. This creates three RAID partitions A, B, and C - think of them as virtual disks - with 2 TB (A), 9 TB (B) , and 5 TB (C) of available storage.  Note the top layer A is RAID-1, because there are only two partitions in it.

 

A 2x2 TB RAID-1  2 TB storage + 2 TB mirror  

B 4x3 TB RAID-5  9 TB storage + 3 TB parity

C 6x1 TB RAID-5  5 TB storage + 1 TB parity

          Total 16 TB storage + 6 TB redundancy overhead

 

These three RAID partitions are then assembled into one volume.  All this is done with standard linux tools.

Message 10 of 17
Highlighted
Aspirant
Aspirant

Re: Mixing drive makes/models within a NAS

Thank you for explanation.

 

 

 

 

The newly added 4tb drive to bay 4 finished syncing.

 

The total storage shown is about 5.3tb

                3.06 from data

                1.52 from  snapshots

                888 gb from free space

 

The total disk capacity is about 9tb

 

Does that seem correct?

 

https://drive.google.com/file/d/0B2b_iVvNvbfJeVlvV2Y5M3FLUnM/view?usp=sharing

Message 11 of 17
Highlighted
Guru

Re: Mixing drive makes/models within a NAS


@FG wrote:

 

The newly added 4tb drive to bay 4 finished syncing.

 

The total storage shown is about 5.3tb

                3.06 from data

                1.52 from  snapshots

                888 gb from free space

 

The total disk capacity is about 9tb

 

Does that seem correct?

 


The rule for capacity is "sum the disks and subtract the largest".  So in your case that's 6 TB (same as was before you upgraded the first drive).

 

Note that the ReadyNAS is reporting space in TiB, not TB.  Your total is ~5.44 TiB  -3.06 + 1.52 + (888.41/1024).  Converting that back to TB gives you 6 TB.

 

After you do the next disk, you will see an increase of 2 TB (to ~7.3 TiB).

 

Going back to the layer cake model - your top layer of 2 TB only has one disk in it.  So there's no way to create redundancy in that layer.  The NAS just doesn't use that space.  Upgrading the second disk lets it use RAID-1 for it.

Message 12 of 17
Highlighted
Aspirant
Aspirant

Re: Mixing drive makes/models within a NAS

 

Thank you Stephen for you explanation, it was very helpful.

 

This morning, 5am, I pulled the smaller 2tb disk from bay 3 of my NAS and replaced it with a 4tb Seagate IronWolf drive.

 

As soon as I did that, I got a message about  volume in a degraded state and Resyncing started.

All of that is what I was expecting.

 

Then about 30 minutes ago, 7 hours after I replaced the drive, I check on the GUI and it said about 20 minutes left to resync.

 

Shortly after that I get 2 message, 

  • Volume volume1 health changed from Degraded to Redundant.
  • Disk in channel 3 (Internal) changed state from RESYNC to ONLINE.

All of that is what I was expecting as well.

 

Now I check the GUI and it is showing another recync progress, I'm 53% with nearly 4hours to go.

All the drives on the GUI show and green light and when I hoover over each drive it says they are online.

 

Should I be worried, is this normal behavior?

 

Message 13 of 17
Highlighted
Guru

Re: Mixing drive makes/models within a NAS

This is the second disk upgrade correct?  So first it resyncs the existing RAID layer, and then it starts building the upper RAID layer.

 

So this is normal.

Message 14 of 17
Highlighted
Aspirant
Aspirant

Re: Mixing drive makes/models within a NAS

Yes, the 2nd disk to be upgraded.

 

OK!. Good to hear that this is normal. I thought I had some hardware that was dying.

 

Can I drop in the 3rd disk to upgrade or should I wait for this current sync to complete?

 

I'm guessing I should wait.

Message 15 of 17
Highlighted
Guru

Re: Mixing drive makes/models within a NAS

Definitely wait until the resync is done (and your volume expands).  Pulling out a disk during a resync generally destroys your data.

Message 16 of 17
Highlighted
Aspirant
Aspirant

Re: Mixing drive makes/models within a NAS

Hummmm....

 

But as soon as the 1st sync was done the volume expanded and I gained another 2tb of capacity/storage.

 

I will wait to be safe.

 

 

Message 17 of 17
Top Contributors
Discussion stats
  • 16 replies
  • 14262 views
  • 2 kudos
  • 2 in conversation
Announcements