Eating Hard Drives

Purchased a 5N in 2015. Three weeks ago I got a RED light on Bay 2, a three year old Western Digital RED 4TB hard drive. I took it out and ran diagnostics on that device for three days. Works.

So I went ahead and replaced it with a NEW Western Digital RED 6TB hard drive. 3 weeks later it is blinking red in the same slot as the one I replaced in July.

Before I spend money that I need for rent, what do you think I should look first? Thank you.

It was recently discovered the WD EFAX drives are SMR drives, therefore we no longer recommend the WD EFAX 2,4 or 6TB drives for use in Drobo.

For a list of compatible drives, see:

Can I really use any hard drive I want in Drobo?

For additional information on the WD EFAX drives:

Thank you for your quick response. No, I don’t have any of the drives that are NOT recommended. The thing is this. After I replaced the 4TB RED with the 6TB and tested it, today I put the old 4TB back in and Drobo likes it now and Data Protection is in Progress. Also, of the six bays, I have 4 WD Reds, two 4TB and two 6TB drives; all the same model #s. I don’t know how to approach Western Digital about a defective drive if it is in fact not defective. Again, thank you.

Maybe the backplane is causing issues. When data protection is finished test this by first TURNING IT OFF, then remove and rearrange the drives, then TURN IT BACK ON. It does not matter which slot the drives are in as long as they are kept together as a pack. If the problem returns to the same slot then I think we found your problem.

** Don’t try moving them around while it’s on however **

No, I moved the 4TB drive and the orange light moved with it. Thank you. Not sure about the WD 4TB issue, the drive has worked fine for 5 years; but diagnostics doesn’t show any issues.

The 6TB was the Recording Technology that WD changed on their regular RED models. I was unaware there was a WD Red Plus that fixes the WD Red SMR issue.

Kudos. WD is replacing the drive. I didn’t know WD issued a PLUS version that addresses the SMR & CMR Technologies.

Thank you, Valorie. No one sung that song better than Amy Winehouse.

I have a similar situation with a 5N2. It is a couple months out of warranty. I did not opt for DroboCare. Seemed expensive relative to cost of 5N2 and drives.

I have a Drobo Gen 2 and a Drobo FS, all still in operation with no issues.

All my Drobo’s act as local NAS archives.

The 5N2 was populated with 4 8TB Seagate and 1 5TB Seagate and mSata cache.

The Seagate drives were all from peeled USB3 drive enclosures.

Things were working fine for a year. It had been set for 2 drive failure protection.

Last week it indicated the 5TB drive needed to be replaced.

I went to Costco and got another 8TB backup drive, I formatted it, peeled it, and swapped it in where the 5TB had been. The Drobo initialized it and then began the rebuilding process. That finally completed in a day or so.

Then it started eating drives.

I exported the event log. So that can be seen. I also have the email alert messages.

The unit is turned off now.

I am not sure what I should do.



I recommend you start a new thread instead of riding the coattails of this one.

That being said… I think clues to your issues may be in this thread, as Seagate is known for producing SMR drives.

For information on recommended drives and drive sizes, see;

Drive Selector Page

Can I really use any hard drive I want in Drobo?

Maximum Volume Size and Largest Size Drive

The current Drobo product line supports drive sizes up to 14TB.
(Note: If your maximum volume size is 16TB, please see: Drobo 5N; Drobo 5D: 64TB Volume Support)

The Legacy products support drive sizes up to 4TB.

Also, see youtube video;

​Adding Capacity to Drobo (5 Bay Drobo)
Adding Capacity to 8 bay Drobo

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I’ve been researching as I try and solve a different issue. But wanted to confirm something in this post.
You say that Legacy products only support up to 4TB per drive and on another page classify the 5N as Legacy. But in this KB article it says the 5N supports up to 14TB ( https://supportportal.drobo.com/knowledgeDocument.html?d25cde07bdbe8b58cf4c94666fefe175e96e1dc891265337e1332803b7f3a57d ) which info is correct?

Thanks for posting.

The referenced document references this…


Looks like you upgrade firmware and then you have to rebuild the whole disk pack. Just upgrading firmware won’t do it.


Hmm, Thanks I missed that second reference. I believe that I am on 3.5.2 but can’t check due to the problem that has me searching the support forums. But I had definitely not done a complete reformat.

I wonder what the real limit was before. I had installed a WD-Red 6TB( claimed to not be SMR) a few months ago and it gave me no complaints/warnings on its size.

Well time to finish writing up my current mess in its own post and see if I get lucky. So far everything involves interrupting the Blinking Yellow and Green lights which everything says not to do. Its been in this state since Sunday(3 days as of post) with some other weirdness just to make it interesting

I wonder what happens in the event you put in a 6 TB in where the max is supposed to be 4 TB. Does it just use 4 TB? Drives these days use LBA. Logical Block Addressing. Looks like it would just use the first 4 TB.

I was excited to see the 5n news, but after looking, I have a DroboFS. (Also a Gen2) Both are still in use.

My 5N2 is about 16 months old. It worked fine that long but then started eating what turned out to be SMR drives. I searched through my old drive stash and found enough good CMR drives to populate the 5N2. Then I bought a new 4 TB CMR. Let it rebuild. Then bought an 8 TB CMR and let it rebuild.

Over time I’ll build back up.

I installed the Drobo Access app and that works.

I do have questions about how often the apps will be updated. I use Linux in other places and I know stuff is continually changing. They have the little colored lights on the apps on the Dashboard. That’s terrible UI design. Between 7-8% of men in the USA are color blind. Good UI design has at least two ways of indicating status. Color and words, or color and symbol.

I also wonder about the hot data cache. Does it just cache reads, or writes, or reads and writes?


On your WD Red drive… I would look its model number up on the WD web site. WD Reds are SMR, and WD Red Pro are CMR. (If memory serves)

On one of your questions…

I have an old Gen2 Drobo which officially only supports 4 TB drives. As a test I’ve inserted 6 and 8 TB drives and Drobo recognized and accepted them with no issues.

Thanks for your reply.

Storage wise did it see them as 4TB each? If it is using LBA, the extra space is ignored.

It’s probably still 16 TB volume size.


Drobo reported them as their marked size. I’m currently using a Gen2 for my “offsite” backups and it’s populated with a combination of 3 and 6 TB drives. I have no qualms about installing larger drives in it when the need arises. The volume size is maxed at 16 TB, however.