[SOLVED] How to Transfer Large Amount of Data When Upgrading Capacity

SparkyTech934

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Hi All,

I recently asked a storage question on the forums related to one of my 4 HDDs (in a RAID 5 array) having some uncorrectable sectors after power loss, and subsequently, needing to replace it. I will more than likely be taking the opportunity to upgrade the storage capacity of the array, (replacing all the drives) and wanted to hear some ideas related to transferring large amounts of data. First, I'll go through a basic description of my setup, and then I'll pose my question below.

I am running an HP Z640 Workstation with Windows server 2019 Standard. The storage setup in the machine is a single boot SSD, and 4 x 4TB WD Gold Re Drives, in a RAID 5 Array. The total capacity of the drives (after allowing the RAID controller to pick a default total size, and formatting within Windows) works out to 10.3TB. Between the SSD and HDDs, I am out of ports and mounting bays for additional storage devices.

My goal would be to replace these disks (HDDs) with something quite a bit bigger, perhaps up to 12TB a piece. This would give me +/- 28TB of total useable space after the upgrade.

Now, I do happen to have a spare HDD large enough to temporarily store all the files, but for arguments sake, let's say that in the future I was going to upgrade the 4 x 12TB disks to a bigger capacity, and they were filled entirely. How would one transfer the data from one RAID array to a new one without the ability to store the data on an independent drive? The reason I pose this question is because I may find myself in that situation, and I'd rather not be stuck when I get there. There are no (readily available) ultra-high capacity HDDs on the market (20+TB), so how could this be done?

I appreciate anyone that involves themselves in this though experiment. Related to this is (and back to my setup as it is), what makes the most sense when I do decide to transfer the data? Should I use Windows backup to create a clone of the files, then restore from it? Or just copy the files as they are to an external disk, and then back to the new array? Is there a universal 'standard' for data transfer? Especially when it comes to important personal data. Thanks!
 

USAFRet

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@USAFRet,

Will the new array automatically resize? I was under the impression that since I allocated only 10.3TB to the original array, when the new 12TB disks are added to rebuild the array, the total capacity would still be 10.3TB since it was initially set up that way. Does the RAID controller automatically scale the capacity with drive size? Thanks for the suggestion!
In my QNAP, yes it did.

Start:
4x 3TB
9TB of array space

Swap in 4x 4TB drives, one at a time. Allowing the array to rebuild with each drive.

In putting in the final 4TB....the final size was 12TB.
This upsizing took 9-10 hours per new drive.

I had a 100% copy of ALL data in it, I just tried swapping them individually to see what happened with the QNAP.
A much faster method would have just been to swap all 4 drives at once, and copy the whole data set into the new 4x4TB array.


Again, though...RAID 5 is NOT recommended with large drives like that.
In the even of a dead drive and replacement, the rebuild time is far too long.

4x 12TB = 36TB RAID 5.
Lets consider you have it filled with 25TB data.

A rebuild with another 12TB can take several days.
If these 4x 12TB drives are the same make/model, and one of them died requiring the replacement....it is not unreasonable to consider that one of the others will also die in the multi day rebuild.
And in that instance...all data is lost.



https://www.quora.com/Why-is-RAID-5-considered-unsafe-for-larger-arrays
https://www.reddit.com/r/sysadmin/comments/ydi6i View: https://www.reddit.com/r/sysadmin/comments/ydi6i/dell_raid_5_is_no_longer_recommended_for_any/
 

USAFRet

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The only thing you can do is bite the bullet, start the copy process, and wait for it to finish.

A RAID 5, to upgrade to larger drives...
Power off
Slot in one of the new, larger drives.
Power up.
The array will rebuild
Repeat again and again until ALL drives are at the new size.
At that point, the array will be of what you think it should be.

But....each rebuild will take approx 1.5 hours per TB of data space in the array.
So....
4x 3TB, a RAID 5 of 9TB space.
6TB consumed.
Changing to 4x 4TB, which will result in an array of 12TB

Each rebuild will take about 1.5hours per TB of data.

Changing these drives one by one (which is the only way to do it), will be about 9-10 hours per new drive.

------------------------------------------------------
Being a RAID 5, this ALSO means you DO have a real backup of all this data on some other storage space. Right?
Do NOT count on the RAID 5 as your only 'backup'.

--------------------------------
Also, RAID 5 is contraindicated for really large drives.
Anything over 4-6TB each is not recommended.
The rebuild time is excessive, and it is 100% pounding on all drives during that process.
 

SparkyTech934

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Jan 22, 2020
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@USAFRet,

Will the new array automatically resize? I was under the impression that since I allocated only 10.3TB to the original array, when the new 12TB disks are added to rebuild the array, the total capacity would still be 10.3TB since it was initially set up that way. Does the RAID controller automatically scale the capacity with drive size? Thanks for the suggestion!
 

USAFRet

Titan
Moderator
Mar 16, 2013
161,164
13,311
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24,450
@USAFRet,

Will the new array automatically resize? I was under the impression that since I allocated only 10.3TB to the original array, when the new 12TB disks are added to rebuild the array, the total capacity would still be 10.3TB since it was initially set up that way. Does the RAID controller automatically scale the capacity with drive size? Thanks for the suggestion!
In my QNAP, yes it did.

Start:
4x 3TB
9TB of array space

Swap in 4x 4TB drives, one at a time. Allowing the array to rebuild with each drive.

In putting in the final 4TB....the final size was 12TB.
This upsizing took 9-10 hours per new drive.

I had a 100% copy of ALL data in it, I just tried swapping them individually to see what happened with the QNAP.
A much faster method would have just been to swap all 4 drives at once, and copy the whole data set into the new 4x4TB array.


Again, though...RAID 5 is NOT recommended with large drives like that.
In the even of a dead drive and replacement, the rebuild time is far too long.

4x 12TB = 36TB RAID 5.
Lets consider you have it filled with 25TB data.

A rebuild with another 12TB can take several days.
If these 4x 12TB drives are the same make/model, and one of them died requiring the replacement....it is not unreasonable to consider that one of the others will also die in the multi day rebuild.
And in that instance...all data is lost.



https://www.quora.com/Why-is-RAID-5-considered-unsafe-for-larger-arrays
https://www.reddit.com/r/sysadmin/comments/ydi6i View: https://www.reddit.com/r/sysadmin/comments/ydi6i/dell_raid_5_is_no_longer_recommended_for_any/
 

SparkyTech934

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Jan 22, 2020
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@USAFRet,

Fair, I'll have to figure out what makes the most sense going forward.

I suppose I could experiment around with the 'software RAID' built into Windows Server 2019 Standard. If RAID 5 is not recommended, then I assume they expect people to use RAID 6? That wasn't very clear. I technically DO have one additional drive bay and SATA slot (the SATA cable is currently occupied by the DVD/CD burner, which I don't need). I can possibly use my Windows Backup to restore the 10.3TB D: drive and create a RAID 6 array going forward (5 x 12TB disks). Thanks!
 

USAFRet

Titan
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Mar 16, 2013
161,164
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@USAFRet,

Fair, I'll have to figure out what makes the most sense going forward.

I suppose I could experiment around with the 'software RAID' built into Windows Server 2019 Standard. If RAID 5 is not recommended, then I assume they expect people to use RAID 6? That wasn't very clear. I technically DO have one additional drive bay and SATA slot (the SATA cable is currently occupied by the DVD/CD burner, which I don't need). I can possibly use my Windows Backup to restore the 10.3TB D: drive and create a RAID 6 array going forward (5 x 12TB disks). Thanks!
Why RAID at all?

It only helps for uptime, in the event of a physical drive fail, and if you really really need uninterrupted operation.
Like if you were running a webstore, and downtime == lost sales.

It does nothing for all the other forms of data loss. Accidental deletion, corruption, ransomware...

And if you have a full backup anyway.....why the RAID?
 

SparkyTech934

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Jan 22, 2020
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Good question. I chose to use a RAID 5 array for the redundancy and the uptime. I have my server up all the time because I run Nextcloud in a VM, and want instant access to my data online. I also use it as a huge file server, and need the large capacity (spreading the data over the disks gives me a larger total space as a single system disk).
 

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