Time machine backups very, very slow

Sorry, but I don't think that this is supposed to be normal behavior. I understand that the first backup after an upgrade may take longer. However, I had already two or three completed backups since the upgrade, and still I had to leave it overnight for the new backup. Notably, this happens when going the officially supported route to to the iMac-attached, network-served disk.

The NAS shows the same behavior. One Backup completed last weekend after ages. Today, I started a backup two hours ago and it's still "preparing". It's connected via Gigabit Ethernet, so it can't be some messed-up Wifi issue.

Before the upgrade to El Capitan, backups to both destinations were super-fast (after all, I had hourly backups, as it's supposed to be). Even after the upgrade to Yosemite a couple of months ago the first backup completed after only a couple of hours.

I would understand that the NAS would be slow, since after all it's an "use at your own risk" thing to use non-Apple storage solutions. Still, it wouldn't really be acceptable if Apple simply broke compatibility with these devices that worked perfectly up to El Capitan.

But none of the hypotheses that were mentioned explains why the perfectly supported route to a harddisk that is served by an iMac is so sluggish that it's basically unusable.

A third-party network-attached storage device (NAS) or router is unsuitable for use with Time Machine, especially if it's your only backup. I know this isn't what you want to hear. I know that Time Machine accepts the device as a backup destination. I know that the manufacturer says the device will work with Time Machine, and I also know that it usually seems to work. Except when you try to restore, and find that you can't.

Apple has published a specification for network devices that work with Time Machine. No third-party vendor, as far as I know, meets that specification. They all use the incomplete, obsolete Netatalk implementation of Apple Filing Protocol.

Apple does not endorse any third-party network device for use with Time Machine. See this support article.

If you want network backup, use as the destination either an Apple Time Capsule or an external storage device connected to another Mac or to an 802.11ac AirPort base station. Only the 802.11ac base stations support Time Machine, not any older model.

Otherwise, don't use Time Machine at all. There are other ways to back up, though none of them is anywhere near as efficient or as well integrated with OS X. I don't have a specific recommendation.

If you're determined to keep using the device with Time Machine, your only recourse for any problems that result is to the manufacturer (which will blame Apple, or you, or anyone but itself.)

Same problem here. Time machine takes ages. I backup my MBP to two locations: one goes to a NAS at home, the other to an external harddisk attached to an iMac in my office. Both were zippy fast until I installed El Capitan, and now one backup takes about 8 hours on the iMac-attached Harddisk, and about 15 hours on the NAS.

Since the iMac-attached external disk is also affected, I have trouble accepting Linc's explanation with the incompatible network protocol. The iMac that serves the backup-disk through the network should support the correct network protocol, shouldn't it?

Huitzilo. wrote:

Since the iMac-attached external disk is also affected, I have trouble accepting Linc's explanation with the incompatible network protocol. The iMac that serves the backup-disk through the network should support the correct network protocol, shouldn't it?

That isn't the problem. As he said, it is that all known third party NAS devices do not implement everything in the Apple specification required for official Time Machine support. That means it may or may not work reliably, particularly after an OS upgrade, so it is strictly a "use at your own risk" kind of thing -- not something very desirable for a backup!

As for why backups to the directly attached Time Machine drive have slowed down, the first one after upgrading to 10.11 can take a very long time (because so much has changed) but subsequent backups should not, unless the drive is very full. That can result in a lot of "thinning" (removing older backups to make room for newer ones), which can take a lot of time to complete.

Huitzilo. wrote:

Notably, this happens when going the officially supported route to to the iMac-attached, network-served disk.

I'm not sure what you mean by the "network-served" part. Is this TM drive backing up anything besides the iMac it is connected to? IOW, what is the "network-served" part all about?

Also, how full is that drive? If it is very full this could affect backup times adversely. You might also want to run Disk Utility's First Aid on it to make sure its file system is OK. (This can take a long time, not just because it may have a lot of files on it but also because the hard links used by TM to save space causes DU to check the same file many times, so this can take quite a few hours to complete even if everything is OK.)

I would understand that the NAS would be slow, since after all it's an "use at your own risk" thing to use non-Apple storage solutions. Still, it wouldn't really be acceptable if Apple simply broke compatibility with these devices that worked perfectly up to El Capitan.

That's one way of looking at it. Another is that they were not really compatible to begin with (for example by not correctly or fully implementing every part of the Apple Filing Protocol that was updated to version 3.3 back in 2009 & is required to support Time Machine) & updating the OS to 10.11 just made that more obvious. After all, Apple has never supported using a NAS as a Time Machine backup drive, so they are under no obligation to make sure any version of OS X works with those devices.

I'm not sure what you mean by the "network-served" part. Is this TM drive backing up anything besides the iMac it is connected to? IOW, what is the "network-served" part all about?

As I said, it's an external harddisk that is attached to an iMac in my office, via USB3. The iMac shares the volume on that disk with my MBP, which is connected to that iMac via Thunderbolt 2. The disk is practically idle, the MBP is the only network client. The iMac is idle, too. In short, perfect conditions, network-wise.

Also, how full is that drive? If it is very full this could affect backup times adversely.

It's not substantially fuller than before the El Capitan upgrade, when backups were still fast.

You might also want to run Disk Utility's First Aid on it to make sure its file system is OK.

That was actually the first thing I tried. All fine.

And in case you ask, the logs don't spit out anything suspicious (at least not when filtering for *backupd*). CPU load on the MBP is not suspicously high during the backup. Neither is it high on the target device, be it the iMac or the NAS. Network throughput during backup is low (at least regarding volume - haven't checked packet counts).

After all, Apple has never supported using a NAS as a Time Machine backup drive, so they are under no obligation to make sure any version of OS X works with those devices.

You sound a bit like a lawyer 😉

But seriously, I fully understand that Apple is not obliged to make sure their upgrade does not break stuff they said they didn't support. Still, please understand that it ***** great deal when an OS upgrade turns your hitherto perfectly functional and fast backup solution into a pile of useless junk.

But anyway, as said above, it's unlikely that the problem is some unsupported feature in the network file sharing protocol, since this problem also affects a volume that is shared over the network by an iMac, which IMHO is clearly a supported case.

Huitzilo. wrote:

As I said, it's an external harddisk that is attached to an iMac in my office, via USB3. The iMac shares the volume on that disk with my MBP, which is connected to that iMac via Thunderbolt 2. The disk is practically idle, the MBP is the only network client.

Are you saying that the MBP is connected to the iMac using IP over Thunderbolt & you are backing up both of their startup volumes to the external USB 3 Time Machine drive connected to the iMac?

If so, does it make any difference if you disconnect the MBP when TM is backing up the iMac to the USB drive?

R C-R wrote:

Are you saying that the MBP is connected to the iMac using IP over Thunderbolt & you are backing up both of their startup volumes to the external USB 3 Time Machine drive connected to the iMac?

No, I only back up the MBP to the USB drive. The iMac has a separate backup mechanism (CrashPlan, using our centralised backup facility). I hardly use the iMac for anything else than sharing that drive and as an external display for the MBP via TDM. Hence, it's unlikely that the iMac's activity interferes with the backup. After all, TM has worked in that very setup for about a year without any major hiccup, and with decent speed.

I now tried resetting TM by deleting com.apple.TimeMachine.plist in /Library/Preferences and re-adding my drives. No change on the NAS backup so far, still "Preparing Backup" three hours in. Will try with the office setup on Monday. I'll also try with the USB disk plugged into the MBP directly instead of going over the network.

Huitzilo. wrote:

I'll also try with the USB disk plugged into the MBP directly instead of going over the network.

I'm still confused about what you mean about "going over the network." As has already been mentioned several times in this discussion, Apple only supports three types of storage devices for Time Machine backups, only two of which involve a network connection:

• External hard drive connected to a USB, FireWire, or Thunderbolt port on your Mac
• Time Capsule or OS X Server on your network
• External hard drive connected to the USB port of an AirPort Extreme (802.11ac) base station on your network

So it still sounds like you have not been using a supported network connection even for your MBP TM backups to the USB drive. Try the direct connection & it should work much better.

• External hard drive connected to a USB, FireWire, or Thunderbolt port on your Mac
• Time Capsule or OS X Server on your network
• External hard drive connected to the USB port of an AirPort Extreme (802.11ac) base station on your network

So it still sounds like you have not been using a supported network connection even for your MBP TM backups to the USB drive. Try the direct connection & it should work much better.

So you're saying an iMac to which I backup over the network does not count as case #2? Note that the TB connection is a perfectly fine network connection.

Huitzilo. wrote:

So you're saying an iMac to which I backup over the network does not count as case #2? Note that the TB connection is a perfectly fine network connection.

Yes. I am saying it does not count as case #2 because it is not a connection to a Time Capsule or (presumably) to a Mac running OS X Server. Only case #1 is a supported one for a Thunderbolt connection -- IOW, if the the TM backup drive had a TB port & it was connected directly to a TB port on the MBP, that would would be a supported configuration, but that is the only TB connection that is.

Hi

I also use a NAS for Time Machine backups, it works, and I can restore ok.

I had two macs which had extremely slow Time Machine backups after upgrading to El Capitan.

What worked for me was to delete .Spotlight-V100 and .fseventsd from the root of my drive.

Now both MacBooks have working Time Machine backups again.

coutts99 wrote:

What worked for me was to delete .Spotlight-V100 and .fseventsd from the root of my drive.

In my desperation to get my backup solution back I tried that. However, this triggered a "deep event scan" by backupd (at least that's what the logs were saying). I assume a deep scan refers to every file on the MBP being compared to every file on the backup. Since the backup is encrypted and on a network drive, this takes a loooooong time. The backup was stuck in "Preparing" for about 12 hours.

Digging through the logs I found a couple of other occasions where a deep scan was triggered in the recent past. I think these are the reasons for the slow backups.

Any ideas what triggers deep event scans, apart from deleting .fseventdb? Maybe aborting a time machine backups?

Yep it will do, but my backups were doing a deep scan every time before that.

They have worked perfectly since.

Huitzilo. wrote:

Any ideas what triggers deep event scans, apart from deleting .fseventdb? Maybe aborting a time machine backups?

See the blue section of http://pondini.org/TM/Works.html for info about what triggers a deep scan.