Time machine error 21 only cured by rebooting Airport Extreme

I have a macbook pro 13" (2009 vintage), and an airport extreme. Despite the fact that Apple says that it doesn't officially support Time machine backups to AE connected disks, I've been doing this since early 2010 (when I bought the AE). Starting about 6 months later after one of the updates to the firmware, every few days Time Machine would fail saying that another application already had the backup files. Nothing I did on the macbook cured this, but I discovered that doing a power cycle of the AE would cure it for a few days. This was annoying, but I was able to live with that. However, with the update to 7.5 firmware this started happening every few hours. I talked to Apple Care support and they suggested that I have the hardware of the AE checked out at an apple store. I did that, and they said that the old one was defective, and gave me a brand new AE (last week). RIght after that, it wanted to install 7.6. Well since then, I can do one backup on the disk. After that, when I try to do another backup I get the dreaded "error 21". However, if I power cycle the AE, things then work again. This tells me that there's a software bug on AE, which, I suspect was introduced in version 7, and has only gotten worse. Even if I don't try to do TM backups, after a few days I can't connect to the disks at all until I power cycle the AE. Anyone else have a problem like this? I wish that I could get Apple to consider that this is really a problem. If I could disassemble the firmware, I could look for the problem myself.

I cannot tell you why your Apple Genius told you what he did, but he/she was dead wrong. Apple sells its Time Capsule product, so they are not interested in making the AEBS a product competitor.
I will give you a little secret for which you will forever be indebted to me.
Open your Terminal application in the Utilities folder and at the prompt enter or paste the following command pressing RETURN after:
defaults write com.apple.systempreferences TMShowUnsupportedNetworkVolumes 1
Miraculously your problem will be Solved.

Similar Messages

Time Machine Error after moving disk to Airport Extreme

I have been using Time machine with a 1 TB, WD MyBook hard drive for the past 2 weeks with no problem. The drive had been connected directly to my Macbook Pro, via the Firewire 800 cable.
Today, I moved the drive and connected it via USB to my Airport Extreme Base Station version 7.3.1.
When Time Machine tried to create the next scheduled backup, I got the following error:
*Time Machine Error*
"This backup is too large for the backup volume. The backup requires 159.8 GB but only 159.1 GB are available.
To select a larger volume, or make the backup smaller by excluding files, open System Preferences and choose Time Machine"
It seems to me that Time machine is trying to do a brand new backup instead of the incremental one its supposed to do.
How can I fix this and have TM recognize that there is already a backup sequence in the disk?
Thanks for your help.

Time Machine uses a different method for creating its archive, depending on how the backup disk is connected. When using a directly connected drive, it uses a time-stamped folder structure. When using a networked disk, it uses a sparse disk image format. Therefore, when you connected that drive to the base station, Time Machine was trying to create a new sparse image archive with the leftover space. It did not find enough space, since your direct connect Time Machine archive was taking up too much space already.
If you want to use it over the network, you'll have to erase the drive and start over with Time Machine.

Time Machine with 2T drive connected to Airport Extreme base via USB

I got this to work - Time machine recognizing the drive in its "choose backup disk" menu.
I used it to store Apple Lossless audio on a big iTunes library, as well as for my Time Machine backups.
Whole system ran fine for 4 months until last week: while I was using iTunes with that remote library, adding audio to it... "Airport has detected a disk error"... My 2TB of disk turned into a very expensive brick.
The disk had to be recovered with Disk Warrior, detecting "19,753 directory entries with incorrect text encoding value" as part of a nice one-page-long list of other errors.
SINCE THEN: no matter what I do, the disk does not show up in Time Machine, even though I can access it via the network exactly as before.
Any ideas are welcome!

Apple does not support Time Machine backups to an AirPort disk (a USB drive attached to an AirPort Extreme Base Station (AEBS)). (ref: Mac OS X 10.5: Time Machine doesn't back up to AirPort Extreme AirPort Disks) Although folks, like yourself, have gotten this to work initially, the long-term stability of the TM backups is highly suspect and why Apple doesn't support it. Sorry!

Can Time Machine backup USB Drive connected to Airport Extreme Base Station

I need a new N based wireless router. I would prefer to get just the $179 Base Station and not the $299 Time Capsule. I already have a nice external USB 500GB drive that I would connect to the AEBS. So, once I have this new wireless router/base station installed at home and I have the external USB drive connected to it, can my new Macbook Air with a USB connected 400GB drive be used to backup what is on the Macbook Air and also backup the 500GB USB drive info that is connected to the extreme base station?
Thanks
tj

I found this when searching Apple's web site but it is old, October 2007, and said it could not be done. Has this changed since then?
Here is what I found.
Mac OS X 10.5: Time Machine doesn't back up to AirPort Disks
* Last Modified on: October 26, 2007
* Article: 306833
Time Machine in Mac OS X 10.5 Leopard can be used to back up to many kinds of Mac OS Extended-formatted drives, but it does not support AirPort Extreme's AirPort Disk feature.
Time Machine can back up to another Mac running Leopard with Personal File Sharing, or to a Leopard Server volume, or an Xsan storage device.

Using time machine backup on disk connected to airport extreme router?

So I've read a number of articles about using an external hard drive connected to the airport extreme base station as a time machine backup. The thing is that I'm writing this in august 09, most of the articles (which say the feature is officially unsupported) date about a year and a half ago. I'm wondering if there have been any developments since then.

I also have this problem -- it started about 2 weeks ago (around July 20?), possibly at the time the new Airport Extreme firmware went into effect. I have two separate Mac laptops that each use Time Machine to back up to different disks that are attached to the Airport Extreme (i.e., each laptop has its own backup-destination disk). Both were working flawlessly before (for more than 6 months); now, each one reliably drops the connection to the disk (produces an error message, and thereafter cannot re-connect to the destination disk until I cycle the Airport Extreme with power-off/on). I had hoped that 10.5.8 would help (the release notes talked about improved stability with Airport connections), but not so.

HT204057 Time Machine back up via ethernet on airport extreme

Forgive me if this is answered elsewhere, i just can seem to find the exact answer.
Can i plug an external hard drive into my airport extreme (4th/5th Gen) with ethernet and carry out Time machine back ups wirelessly? I've tried with USB connection to it and it takes far too long - overnight and its still not finished. also i'd like to be able to transfer / store independent files on the hard drive in addition to the back ups, via wireless?
the other option is via USB 3 directly into my rMBP to do the initial back up and then plug this into the AP extreme, will it do top-up back ups from here which i guess will only be things i've changed since the last back up - will this work and if so which option would be best.
Truly i'd love to buy a new time capsule but after upgrading to my rMBP, i'm low on funds for a while..
thanks,

Why did Apple stop supporting time machine back-up via USB hard drive connected to Airport Extreme?
Time Machine backups are supported via USB hard drive connected to the AirPort Extreme"ac" version.
Time Machine backups were not supported via USB hard drive connected to earlier versions of the AirPort Extreme.
Some users who tried this on earlier version AirPort Extremes seemed to have some success with Time Machine backups....some had moderate success and some had no success with this. Count me in the "no success" category.
See the topic about Time Machine support for USB disks in this Apple Support document:
http://support.apple.com/kb/HT5924?viewlocale=en_US&locale=en_US

Time Machine fails with drive connected to Airport Extreme

First of all, I've had myriad problems with Time Machine, even when it was connected directly to my MBP. But after the recent updates, I installed them and hoped it would work wirelessly. I re-formatted my 120GB OWC drive (my MBP has 30GB available of 120GB). I have already been down the road of making sure I've formatted the drive correctly.
I excluded my system folder, my entourage identity, downloads, and my Parallels Windows XP file from the backup. I connected the drive to my Airport Extreme (not the gigabit version) and started the backup. Basically, it gets about 5 GB into the backup, moving very slowly, and then fails, saying that it couldn't locate the drive. And that part is true--I can't seem to locate the drive on my network anymore either. And eventually, after another hour or so, my Airport Extreme drops as well, and isn't even available. Even when I unplug the AE, and plug it back in, it still doesn't show up...but after about an hour or so...it pops back up and is available, working fine. My iPhone sees the same problem with AE dropping and then coming back. When the wireless service drops, I can plug an ethernet cable into the AE and I can access the internet fine, so it's not the cable modem (Time Warner).
Is anyone else seeing this problem? I'm no guru and appreciate that Macs just seem to work correctly. But Time Machine is making me pull my hair out. It's been an unmitigated disaster from start to finish.
Appreciate any help!

This is probably the most sensible post I've read on the issue. I've spent the last 2 days trying to get my 500GB LaCie Quadra hard drive to work with my Airport Extreme (the square one, yes .
I've formatted it correctly with the Disk Utility (multiple times!).
Airport Utility sees it just fine. I can back up to it when it is connected directly to my MacBook via USB.
But when the drive is connected via USB to the Airport Extreme, Time Machine doesn't see it -- unless I turn on file sharing with guest access read and write. That seems less-than-secure to me even if my network is protected.
Without guest access the drive appears in the shared section of the Finder, but I can't connect to it. I've tried all three combinations under "Secure Shared Disks" but none of them work.
Seems like its just too flaky to use an external disk connected to the Airport Extreme.
Happy to be pointed in the right direction... are there specific file permissions I should be setting my external drive to?
Thanks,
Rich

Time machine not recognising external disk on airport extreme

Hi
I have connected a LaCie d2 Quadra disk to the usb port on my airport extreme.
The disk is formatted as HFS+
If I look in Finder (with Bonjour computers enabled as displayed) I can see the external disk through the airport extreme. I can enter the disk and see the drive (it is connected), but I cannot add files to the disk.
If I open Time Machine setup, I cannot see any external disk at all.
If I look in Airport utility, I can see the d2 Quadra listed as an external disk on the extreme, and I have set it up for File Sharing (using the device password)
Can anyone advise why Time Machine (OS-X Yosemite 10.10.1 on iMac) cannot see it?
And what to do to get it connected please to allow backups from any mac user's machine?
Thanks
Andy

So, LaCie advised to connect direct to Mac to check all ok. It was.
As soon as the HD was plugged in directly, TM recognised it and asked if I want to use it for backup. In Finder, the d2 Quadra appears, I can open it, and transfer files directly to and from it.
For reference, the Airport Extreme is connected via Ethernet to the iMac I am using (so no WiFi in this particular chain of connectivity), and the Extreme firmware is the latest (7.6.4) for the model (802.11n)
The issue is that connecting to the USB port on the Extreme, I cannot get the HD to operate like this!
LaCie now state that they cannot help further!!!
Does anyone have any idea why the Extreme is not sharing the HD as it is meant to?
Thanks
Andy

Leon and I installed the Time Machine does not work. to the Airport Extreme is connected MyBookWorld II. Snow leopard with everything working. Leon sees the drive, but you can not connect to it. can not be seen in disk utility. Thank you for your help or

Leon a Já instalované Time Machine nefunguje. na Letiště Extrémní je připojen MyBookWorld II. Sníh leopard s vše pracovat. Leon vidí pohonu, ale nemůžete se k němu připojit. nemůže být viděn v disk utility.
Děkuji za Vaši pomoc nebo rady
Petr

Here's how you can potentially use your AirDisk with TimeMachine (beware that YMMV), but it should work as it works with every other "unsupported" device.
1) Mount your AirDisk so it appears on your Mac
2) Open Terminal.app
3) change directories to the AirDisk's root folder located in "/Volumes"
ie: cd "/Volumes/AirDisk Name"
4) execute this command to "bless" the drive to be used with time machine:
touch .com.apple.timemachine.supported
5) Start TimeMachine and if all went well, it should recognize your AirDisk drive and use it for TM.
This should also work on NFS shares, SMB shares, AFP shares, basically anything. It has worked up until the last developer seed, so unless they yanked this at the last minute, it should still work.
Now, the reason why Apple removed this feature may be due to the unreliability of the AirDisk, so be cautious.

Time Machine Read only error launches airport

I have a partitioned external and use Time Machine on an OSX10.5, and SilverKeeper for the OSX10.4.11 Mac. Everything's been fine until yesterday. Backed up the 10.4 machine with the designated partition, drive 'hung', computer crashed. So, now, the partition for the Time Machine computer doesn't work, the MAC Silverkeeper appears fine and I get the "Time Machine Read only error" on the MacB Pro 10.5. I can "read/write" for the other partitioned, can verify and repair. No go to repair the "Time Machine" partition. And here's the best part: If I choose "NONE" in Time Machine Preferences to unchoose that particular drive, The computer launches the Airport Express Utility and offers my Airport express as a choice for a drive. What's up with that?

I have a partitioned external and use Time Machine on an OSX10.5, and SilverKeeper for the OSX10.4.11 Mac. Everything's been fine until yesterday. Backed up the 10.4 machine with the designated partition, drive 'hung', computer crashed. So, now, the partition for the Time Machine computer doesn't work, the MAC Silverkeeper appears fine and I get the "Time Machine Read only error" on the MacB Pro 10.5. I can "read/write" for the other partitioned, can verify and repair. No go to repair the "Time Machine" partition. And here's the best part: If I choose "NONE" in Time Machine Preferences to unchoose that particular drive, The computer launches the Airport Express Utility and offers my Airport express as a choice for a drive. What's up with that?

Time Machine read only error & dissapears

I have been running time machine on a MacBookPro MacOS x 10.5.8 for 2 years.
Last week for the first time I got the "External Drive is Read Only" error. I followed the instructions in Troubleshooting on verify and repair but it didn't work (details below). I bought a new external drive configured for MAC OS Extended Journaled format and it worked for 5 days before giving me the same error and the same problems reported on verify. I don't want to use the install disk again because it didn't work last time (and it is 10.4.9 not Leopard - I upgraded by download).
I am at my wits end here. Given that the problem occurred on two different external drives I suspect a problem with my OS.
Details of errors (more or less the same both times):
Time Machine Error - Time Machine "Backup volume is read only"
Finder initially showed that the back up folder was read/write for my user ID and the drive was read/write for the system (not sure because the drive now doesn't appear in finder or in Time Machine ("storage location cannot be found" message)
Disk Utilities: Repair disk option was unavailable Verify disk was available
Verify disk showed a lot error messages including a lot in red: e.g. "Incorrect number of directory hard links" "Incorrect number of threads" "Invalid Directory Item Count" "Invalid volume file count" - on the second drive (not the first) it could not complete the verify - error message Verify disk failed: Error: 'Filesystem verify or repair failed.'
Repair disk was available on the Installation disk (10.4.9) - I ran it on the first external drive but it could not repair ANY of the errors. I haven't tried to run it on the second drive

mysteryrare wrote:
I upgraded to Leopard by going to the Apple site and purchasing the upgrade from there. It was a download.
I never heard of that. I've always been told that OSX isn't available that way. (It must have been a massive download!)
I will try Apple support but I am in Australia and it can take a while for things to get here.
Yes, but if you ever have to reload, or even do a +*Repair Disk+* on your boot drive, you'll need it.
The Disk utility is v 11.1 (252.4) dated 2007.
Yes, that's the right one (I was afraid you had a Tiger version).
I did not format the second drive myself. I purchased it as a Mac only external drive. I checked the format before and in Disk utility - it is definitely Mac OS Extended (Journaled) in both the disk and the partition. The Partition Map Scheme is "Apple Partition Map" which is supposed to be alright for an intel machine (which mine is). Should I change it to GUID?
No, that's fine for TM. Only if you want to install OSX on it do you really need GUID. It's likely not a problem here, but most drives come with various software from the makers, often backup and/or management apps. On occasion, some will be running occasionally or constantly, interfering with TM or other things. That's why we usually recommend that a new drive be erased and reformatted.
I did format the first drive myself before I used it. My memory of how I set it up is a little fuzzy but it worked for a long time. After the Time Machine failure, the Disk Utilities showed different format for the drive and the partition - which bothered me a little and was one of the reasons I bought a new drive. I was thinking about reformatting the drive but now I won't until I know what has gone wrong.
That could have been part of the problem with the first one, but it's doubtful.
So what do we do now?
I don't recall hearing that DU wouldn't even offer +*Repair Disk+* on a drive it could recognize. But if DU won't repair the file system, and you don't have +Disk Warrior+ or other such apps, your only choice is to erase it and let TM start over. In this case, it's probably worth the time to see if DU can write to the entire disk.
Select the top line of the drive, then click the Erase tab. Then click +Security Options+ at the bottom, then +Zero Out Disk+ and OK on the next screen, then confirm.
That will, of course, take quite a while. If it fails, the disk is toast. But it should be covered by warranty, at least.
If the zero-out succeeds, it doesn't necessarily mean the disk is good, but since it's new, it probably is. TM will, of course, do a new, full backup, which will also take a while.
What sort of disk is this? LaCie had a run of bad power supplies lately (your symptoms don't seem to be the same, though), and WD has some firmware updates. You might want to check with the maker for driver and/or firmware updates.

Time Machine Error. Backup is too large for the backup disk. Backup requires 289.28 GB but only 177.01 GB are available.

My Mac has not been backing up for some time. Tried Apple Support, but couldn't figure out problem.
Receive the following error...
Time Machine Error
This backup is too large for the backup disk. The backup requires 289.28 GB but only 177.03 GB are available.

See #C4 in Time Machine - Troubleshooting.
If that doesn't clarify the situation, post back with:
How much data is on your internal HD (and any others being backed-up)?
How large is your Time Capsule?
Is there anything else on the TC besides these backups? If so, what and how large?

Time Machine Error, Backup to large - 496 avail and only 79 needs backed up

I have a 1 TB TM with 496.9 GB available (I already have 1 computer backed up on TM)
The second computer I want to back up has 80 GB used of a 500 GB HD.
Time Machine prefs show 496.9 GB available on TM and shows the back up will be 79.1 GB total.
But I get a error each time I try to back up saying " Time Machine Error, This backup is too large for the backup volume. The backup requires 614.1 GB but only 496.9 are available."
Two questions:
How can 496.9 GB be to small for a 79.1 GB backup?
Why does a 79.1 GB backup require 614.1 GB of space?
Thank You
Doug

Here's what Backup Buddy says:
Starting standard backup
Backup destination alias resolved to path: /Volumes/Doug's Time Capsule
Disk image /Volumes/Doug's Time Capsule/Jackie’s_001b63b59975.sparsebundle mounted at: /Volumes/Backup of Jackie’s
Backing up to: /Volumes/Backup of Jackie’s/Backups.backupdb
Event store UUIDs don't match for volume: Backup of Jackie’s
Event store UUIDs don't match for volume: Macintosh HD
Backup content size: 432.7 GB excluded items size: 0 bytes for volume Backup of Jackie’s
Backup content size: 80.2 GB excluded items size: 1007.5 MB for volume Macintosh HD
Starting pre-backup thinning: 614.25 GB requested (including padding), 496.85 GB available
No expired backups exist - deleting oldest backups to make room
Error: backup disk is full - all 0 possible backups were removed, but space is still needed.
Backup Failed: unable to free 614.25 GB needed space
Backup failed with error: Not enough available disk space on the target volume.
Ejected Time Machine disk image.
Ejected Time Machine network volume.

"Time Machine Error The backup volume is read only"

Lately, every time I try to backup to my Time Capsule using Time Machine it fails and I get a message saying "Time Machine Error The backup volume is read only. To select a different volume, open system preferences and choose Time Machine" So I do that and I see the Time capsule listed. I don't want to select anything but the Time Capsule, cuz what else do I have, right? Am I wrong in assuming the "backup volume" is the Time Capsule? Anyway, I have tried changing the permissions on the time capsule, but when I get the "get info" box for the time capsule, there is not an option to change those settings, they are grayed out. Every thing worked well for about a week and then this started. My backup volume must have been "Read & Write" at first, because I can see what was backed up when I open Time Machine. Anybody have a clue what's going on? How can I make the back up volume "Read & Write" again and why did it change to "Read Only?"

Nope, I am using the same passwords as ever, both users have the same password, BTW. The password I gave to the Time Capsule is different, tho, but that password is for the wireless aspect of the Time Capsule, so that wouldn't have anything to do with it, would it?
I also get a message box that says "Disk Repair The disk "Backup of XXX's Computer" was not repairable by this computer, it is being made available to you with limited functionality. You must back up your data and reformat the disk as soon as possible." This box appears in conjunction with the appearance of the Norton's virus scan box scanning the time capsule.

Time machine error: The backup disk image could not be mounted

Time Machine worked OK for several months. Now I get this error every 10 minutes or so.
I unplugged Time Machine capsule and "Change Disk" in Time Machine options.
Nothing helps, I continue to get this error.
I cannot Enter Time Machine either. "Connecting to Server, Connecting to backup" does not work.
Help please because I will probably have to archive and reinstall Leopard. I need the backups,
Christine

Christ1ne,
Before you reformat the disk, consider these causes of this error.
*_"The Backup Disk Image Could Not Be Mounted" (Console - “Failed to mount disk image”)_*
First, it is important to distinguish this error message from another, similar Time Machine error that states “The backup volume could not be mounted”. This is important as the causes and cures for these two errors can be very different.
Consider each topic below separately. When one option does not resolve your issue, then move on the next one.
*Unmount the Backup Disk Image* (TC)
If, for some reason, you have manually mounted the Time Machine backup disk image (sparsebundle), or Time Machine failed to eject it after the previous backup, subsequent backups may fail. (Console - “Failed to mount disk image”… “Backup failed with error: 21”)
Eject the backup disk image (white drive icon) by either clicking the little Eject icon to the right of the disk image in the Finders’ Sidebar, or Ctrl-Click the drive icon on the desktop and select “Eject” from the contextual menu. Now try backing up again or launching Time Machine to view previous backups.
*“Disconnect All Users…”:*
If your Time Machine backup drive (“Backup of Users Computer”) is mounted on your desktop or in the Sidebar of the Finder window. then Time Machine may think the drive is already in use. Alternatively, if the Time Capsule hard disk has been recently accessed by a Windows machine, it may not have fully relinquished control. Do the following:
Open Airport Utility and select the Time Capsule on the left.
Click “Manual Setup”.
Select “Disks” at top of window.
Click “Disconnect All Users…” at bottom of window.
Close the Airport Utility.
Now try Backing up again.
One poster reported: “I got it resolved. Apparently it had to do with one of the files being open on the disk from the drive. I had browsed the disk with one of my windows boxes here and it must have left one of the folders "open". Anyway, I rebooted the TC and we are good to go now.”
*Proper Computer Name* #
Make sure your computer has a proper name. Go to System Preferences --> Sharing. Time Machine needs to differentiate your computer from others on your network (i.e. "Bills MacBook" or "Office iMac"). If the "Computer Name" field is blank, create a name. Realize that if this step is necessary, you will likely have to start the Time Machine backup process over again and do another full initial backup.
According to this article, [http://support.apple.com/kb/TS1760], Time Machine may experience problems if your computer name includes certain characters. Make sure the computer name only includes ASCII characters from the following set.
(0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ)
Once a change in the computer name occurs, you should stop and restart Sharing on the affected computer. Uncheck and then recheck Sharing in the Services list on the left.
# Try removing the apostrophe from the disk images name (sparsebundle).
*A Stalled .inProgress Files:* #
It may be that the previous backup attempt was ungracefully interrupted leaving remains that Time Machine can’t deal with.
Stop any current backup attempt. Choose “Stop Backing Up” from the Time Machine menu.
Open the Time Machine Preferences and turn “OFF” Time Machine.
Open your Time Machine drive.
Open the folder labeled “Backups,backupdb”.
Now open the folder containing backups of the computer in question.
Are there any “.inProgress” files there. Delete them by dragging the file to the Trash. Or Ctrl-Click the file and select "Move to Trash" from the contextual menu. (Give this time as deleting a large file on an external disk can take a while.)
Turn Time Machine back “ON”. Now try backing up again.
NOTE: If the above procedure becomes impossible to perform, try accessing the disk image from another Mac. Some have discovered that attempting a repair from another computer succeeds where the original computer failed.
Let us know if any of the suggestions above helped to resolve your issue.
Cheers!

Time machine error 21 only cured by rebooting Airport Extreme

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