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Question: Time Machine network backup disk could not be accessed

Hello All,


I've recently started to receive the following error message following recent updates to High Sierra 10.13.4 (17E199).


Time Machine couldn't complete the backup to "<Drobo Hosted / Time machine Network Share>"


"The network backup disk could not be accessed because there was a problem with the network username or password. You may need to re-select the backup disk and enter the correct username and password."


This error is intermittent and appears to happen over night (power nap is active). For the past few weeks it was only affecting my iMac, but I've recently noticed its happening on my MacBook Pro now as well.


Forcing a backup to start isn't met with the same message, backup completes normally. No changes to the network share's password or username have occurred.


Thoughts?


User uploaded file

iMac, macOS High Sierra (10.13.4), 27' Late 2013, 3.5 Ghz Core i7

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Answer:
Answer:

**UPDATE** - Resolved


Appears the Keychain for this process was corrupted. Deleting the keychain associated with the share drive and reselecting the drive via Time Machine preferences appears to have resolved it.


Backups are working as expected.

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Apr 22, 2018 10:29 AM in response to John Galt In response to John Galt

Thank you John for your reply and the link. However, note I've been using this setup for several years without issue. It allows me to centralize all of my mac device (5) backups to one safe/redundant location and it works flawlessly 99% of the time.


The link provided doesn't appear to directly address the error message I posted. My issue remains unresolved.


Recent Troubleshooting:

- Contacting Drobo

- Reset KeyChains for Drobo share

Apr 22, 2018 10:29 AM

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Apr 22, 2018 10:35 AM in response to Jason Golden In response to Jason Golden

John Galt is correct about NAS devices not being suitable for Time Machine backups. They will work for a while until the Time Machine gets too large for the NAS drive to handle the requirements of Time Machine then you end up in the state that you are now.


It sound like it has just taken longer for the problems to show up in your case.

Apr 22, 2018 10:35 AM

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Apr 22, 2018 11:10 AM in response to Allan Eckert In response to Allan Eckert

Thank you Allan, however, the reference John provided appear to contradict your guidance.


User uploaded file

Additionally, the Time Machine compatible shares created by the drobo are sized to support my needs and none of them are near 90% with the Drobo's 5.39 TB of space only 47% full.


Mac Mini - unaffected: Auto backup's continue without error 1.53 TB of 2.15 TB 71% of TM Share Used

iMac - affected: Auto backup's fail, manual succeed without error 2.76 of 4.29 64% of TM Share Used

MacBook Pro (current Beta) - affected: Auto backup's fail, manual succeed without error 2.65 of 3.22 82% of TM Share Used

MacBook Air - affected: Auto backup's fail, manual succeed. Share's Volume with MacBook Pro


I would also point out that if triggered manually all devices backup normally without error. If this was a capacity issue I would expect them to fail as well.


I've posted this issue on the Vendor's support site as well.

Apr 22, 2018 11:10 AM

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Apr 22, 2018 12:14 PM in response to Jason Golden In response to Jason Golden

I understand. The fact remains that Apple does not now, nor have they ever supported anything other than the devices specifically enumerated in their Time Machine technical support documents.


The error you describe is typical of nonconforming implementations. It will never be reliable. Search this site for hundreds if not thousands of reports similar to yours, dating back to Time Machine's original implementation in Leopard.


It allows me to centralize all of my mac device (5) backups to one safe/redundant location and it works flawlessly 99% of the time.


I have used each of the various Time Machine configurations specifically enumerated in Apple's Time Machine technical support documents. They have worked flawlessly 100% of the time, as it has for all my Macs in all their locations, using every conceivable supported configuration, since Time Machine's inception over a decade ago. No failures to back up or restore, not a single one, ever. That is not 99% or even 99.999% reliable. It's 100%.

I also understand that everyone's backup requirements are different. If you consider 99% reliability an acceptable metric that is your decision to make, but any backup strategy less than 100% reliable would be unsuitable for my requirements. Contact "Drobo" as you wish. They will blame everyone but themselves.


How to use Time Machine to back up or restore your Mac - Apple Support refers to a "network backup". In that context they are referring to these specific devices:


  • An AirPort Time Capsule's built-in drive (any model)
  • An external USB drive connected to an AirPort Time Capsule (any model) or AirPort Extreme (802.11ac model only)
  • Network volumes connected using Apple File Protocol (AFP)


Which one of them corresponds your "Drobo"? The answer is none of the above, because it does not use AFP, a proprietary Apple protocol they license to no one. Instead, non-Apple NAS devices use a buggy open source poor imitation of it that tends to break with every macOS upgrade and many updates.


It gets worse:

The most common format for a Time Machine backup disk is Mac OS Extended (Journaled) format.

Time Machine also supports Mac OS Extended (Case-sensitive, Journaled), Mac OS Extended (Case-sensitive, Journaled, Encrypted), and Xsan formats. If your disk uses the Master Boot Record (MBR) partition type, some partitions might not be available for use with Time Machine.


Which file format does yours use? Most non-Apple networked disks are not formatted Mac OS Extended (Journaled). That's a fundamental Time Machine requirement. Nothing else will be reliable.


The link provided doesn't appear to directly address the error message I posted.


Sure it does. It tells you everything you need to know. It does not mention a "Drobo" because it is not an option.

Apr 22, 2018 12:14 PM

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Question marked as Solved

Apr 24, 2018 4:55 PM in response to Jason Golden In response to Jason Golden

**UPDATE** - Resolved


Appears the Keychain for this process was corrupted. Deleting the keychain associated with the share drive and reselecting the drive via Time Machine preferences appears to have resolved it.


Backups are working as expected.

Apr 24, 2018 4:55 PM

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Question: Time Machine network backup disk could not be accessed