Need Recommendation on Expanding Synology DiskStation 412+NAS Capacity

MrChip2 used Ask the Experts™

I have a Synology Diskstation 412+ NAS in my home office that is nearly full.  The NAS was purchased November of 2012 and has 4 Western Digital 2TB Red drives configured in RAID 6.  I am currently using 3.2 out of the 3.6 TB capacity (89%) and need to increase the capacity to 6-10 TB.

When I purchased the NAS it was being used for both work and home files. The work files involved backing up a web server,  a file server and 1 workstation while the home files included pictures and videos.  I decided to configure the drives in RAID6 so that I could weather up to two drive failures. In the past 5 years I had one drive go bad and the replacement was super easy with no data loss or downtime. I also have a new spare 2TB Red drive in a box in case another drive fails.

My work situation has changed and I no longer need to be able to handle two simultaneous disk failures. In order to keep my RAID 6 and increase my capacity, I think I have to replace all four drives.  If I was starting out today, I would rather have two 8TB drives mirrored and have a third 8TB drive available for a spare. I am looking for advice on the best way to expand my capacity while not breaking the bank.  FYI, I purchased a Western Digital 8TB EasyStore external drive that I will use to backup the NAS before I make any changes. I currently backup my NAS volumes to multiple smaller drives.

Here are the options I am considering:

1. Reconfigure current 4x2TB system to RAID 5 increasing capacity to 6TB  
 - Benefits: No out of pocket cost. Also already have spare 2TB drive on hand in case one drive fails.
 - Drawbacks: 1) must "rebuild NAS" meaning: first backup entire NAS, reformat drives into RAID 5, recreate volumes, and copy all data back to NAS, 2) only yields a 2TB increase in capacity, so likely short-term solution, 3) if NAS fails must rely on backup to avoid data loss

2. Purchase two new 8TB Red drives, mirroring them to get 8TB capacity and leaving two bays empty.
 - Benefits: 1) doubles capacity to 8TB which should be enough for multiple years, 2) data now stored on two brand new drives (presumably more reliable), 3) simple mirroring means if NAS dies I can recover files off of either drive in case backup not current
 - Drawbacks: 1) will cost about $500, 2) must rebuild NAS
 3. Maintain RAID 6 and upgrade all drives to 4TB Reds to double capacity to 8TB.
  - Benefits: 1) I think there is no need to rebuild NAS, with hot swap I think I can swap one drive at a time and end up with 8TB capacity RAID 6  NAS
  - Drawbacks: 1) will cost about $600 for 4x4TB or $820 for 4 x 6TB with no spare drive on hand, 2) if NAS fails must rely on backup to avoid data loss

I am leaning towards Option 2 unless experts think that my Synology hardware is nearing its end of life.  If I am going to likely need a new NAS in the next 12-24 months, I may go with Option 1 and wait until the NAS fails.  When it does, buy a two bay NAS thinking by then cost of NAS and drives will be lower.

I am looking for advice on the best approach as well as suggestions on best way to backup NAS if I end up choosing Option 1 or 2. Please let me know if you have any questions.

Thank you!
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RobertSystem Admin
Here is the official guide

However if you use the process of switching out 1 drive at a time be sure it finishes rebuilding before you do the next one.

Regardless of the option you choose if you have the ability to do so I would recommend to backup the data first.
If that is an option then the cleanest way is to backup - swap disk rebuild your array and then restore the data.
With Disks that size DO NOT go to RAID-5, the risk of a second disk failing while the first one rebuilds is too high!

Go for the bigger drives!


Thank you both for your comments/  I have a few follow-up questions:

1. What is the best way to backup the NAS on this new Western Digital 8TB EasyStore?  I wish there was a way to use something like Robocopy so the files are backed up in a way that I can view them directly from Windows.

2. Gerald, when you say go for the bigger drives, do you mean Option 2 or Option 3?  Also, prior to this EasyStore I have never purchased a drive larger than 2TB for network/server use.  Are there any technical reasons why I should prefer a 6TB or 8TB or 10TB drive?  Or should I buy the largest drive I can afford budget-wise?

3. Any suggestions where I can find a great price on these drives?
System Admin
I believe WD has a backup tool for the easystore however i am not familiar enough with it to speak to its functionality. (i believe it uses cloud based storage to backup)

I would use robocopy and do the transfer but it is going to take a while if you have 8 TB of data (and obviously you would need equivalent storage in another system to do so.)

There are backup software available that can backup nas storage but they can get pricy as well as needing a tape drive or something as a backup target.

As for Gerald's comment there is a bit of debate among the technical community about creating raid volumes on larger sata drives related to the amount of time a rebuild takes. That said I have setup raid volumes on large sata drives in the past with out issue, in my experience although it is possible I have never seen a failure of a second drive within the time it takes for a rebuild. So if you want the details of what Gerald is talking about you can do a google on "Use of RAID5 on large sata disk"
Basically it can take days to rebuild the array and the odds of a second failure are higher so you are taking a little risk if you use raid 5 on large sata drives but if you have backups it can help mitigate the risk.

as for #3
last time I searched prices on amazon were better but as they change frequently i would just suggest shopping around. (right now with Christmas sales you may get better deals)


Thank you both for your comments. I did some research and learned that some Western Digital EasyStore external HDDs actually use WD Red drives.  I found 8TB EasyStores on sale for $150 and purchased four of them.  Opened two so far and found actual they contain fully labeled red drives. A third drive I have connected to my PC as an external EasyStore for backup.  So my plan is to do the following:

1. Backup my NAS to one of the EasyStore drives.  Also use Synology software to backup the NAS configuration itself.
2. Delete my current RAID6 drive configuration, pull my four 2TB red drives and install 2 8TB red drives and configure them in RAID1 mirror.
3. Restore data from backup
@Robert - No Debate among storage experts - it doesnt matter what the bus is, SAS/SATA/FC/etc, Disks over 750GB are now not recommended by any storage expert for use in RAID-5, the risk of that second failure has now become unacceptably high!


Gerald, thanks for the information.  I will definitely go with RAID 1.  I am about to call Synology tech support to ask them a few detailed questions on the steps to do this.

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