Can I use TM with NAS?

Time Machine should work with any NAS provided the volume is formatted to HFS+ (Mac OS Extended Journaled.) The Apple Time Capsule itself is an NAS designed for Time Machine.

Apple does not support or recommend using a NAS with Time Machine. Even if the NAS maker says its product supports Time Machine, it may or may not work reliably, now or with future updates to OS X.

chroot wrote:

Time Machine should work with any NAS provided the volume is formatted to HFS+ (Mac OS Extended Journaled.) The Apple Time Capsule itself is an NAS designed for Time Machine.

There is more to it than that. To begin with, refer to Backup disks you can use with Time Machine - Apple Support for the types of devices Time Machine officially supports. Note that minimally any network file server must support Apple File Protocol (AFP) file sharing & that Apple says it should be running OS X v10.5.6 or later.

Obviously, commercial NAS devices don't run any version of OS X. Typically they run some custom OS that may include a third party server implementation of AFP like Netatalk. However, there are several different AFP versions & to support Time Machine properly they must fully support at least AFP version 3.0. Specifically, they must support Unicode file names, POSIX and access control list permissions, resource forks, named extended attributes, advanced file locking, directory level hard links, & service discovery.

Even what that is true, the file system(s) used by the NAS usually are not internally what they appear to be to client devices, so for example there may not actually be a Mac OS Extended (Journaled) volume in the NAS. This can cause problems, particularly with the integrity of the hard links Time Machine depends on to make one copy of a file appear to be in many different backups.

claudio263 wrote:

The two answers are really different...I'm still confused 😟

The bottom line is Apple does not support using Time Machine with a NAS. If you use a NAS for this, your only support is from its maker. How well it works depends entirely on them & how well they implement what is actually a proprietary protocol owned by Apple.

Personally, I would not trust anything as important as a TM backup to any device Apple does not support, but it is up to you to decide if it is worth the risk to do so.

claudio263 wrote:

Thanks guys 🙂

The two answers are really different...I'm still confused 😟

You're right some mis-information there.

• Apple do not certify any NAS drives for use as a Time Machine backup however this does not mean they will not work
• The NAS does not need to be formatted as HFS+ in fact the overwhelming majority of NAS drive systems use EXT3 or EXT4 as their underlying format and this is actually totally irrelevant, with a NAS you are not mounting it as an external drive you are mounting it as a network drive, so the equivalent requirement is that it must support AFP (Apple Filesharing Protocol)
• As mentioned Apple do not certify any but I can speak from personal experience that the NetGear ReadyNAS range work fine and QNAP and Synology are also supposed to work

(One could argue that Apple's own Time Capsule counts as a NAS and it definitely is certified to do Time Machine network backups - it is made by Apple after all.)

With specific reference to your QNAP TS-853 Pro, here is what QNAP themselves say about it

Apple Time Machine is also supported to provide Mac OS X users with a solution to effortlessly back up data to the TS-853 Pro.

Note: If you have an older NAS product you may need to upgrade its software. As R C-R mentioned it needs to support certain minimum versions of the AFP protocol and this typically means having certain minimum versions of the NetAtalk software. Even the very oldest ReadyNAS model can be upgraded to work with current Mac software, in fact dedicating a very old NAS to just Time Machine duties is a good use for such older models.

John Lockwood wrote:

The NAS does not need to be formatted as HFS+ in fact the overwhelming majority of NAS drive systems use EXT3 or EXT4 as their underlying format and this is actually totally irrelevant, with a NAS you are not mounting it as an external drive you are mounting it as a network drive, so the equivalent requirement is that it must support AFP (Apple Filesharing Protocol)

It is not exactly true that the underlying format is irrelevant. To support every Time Machine feature reliably, the NAS must somehow duplicate every aspect of at least one of the formats Time Machine supports, which are:

• Mac OS Extended (Journaled)

• Mac OS Extended (Case-sensitive, Journaled)

• Mac OS Extended (Case-sensitive, Journaled, Encrypted)

• Xsan

• Master Boot Record, but with very limited support

For instance, it must somehow preserve OS X access control lists (ACL's). As explained in the POSIX ACLs section of http://netatalk.sourceforge.net/3.1/htmldocs/configuration.html#fce, POSIX ACLs are much more limited & inflexible than OS X ones. As explained in the Mapping POSIX ACLs to OS X ACLs section, "it is usually impossible to find an exact mapping so that the result of the mapping process will be an approximation of the original ACL's." In fact, as mentioned, the NetAtalk afpd mapping process will silently discard some OS X ACLs, inheritancewill not always be preserved, & there will usually be an increase of granted permissions.

IOW, a NAS that relies only on NetAtalk, even the most recent version, for AFP support will not preserve all OS X ACLs.

How big a deal is this? For most user domain files it won't matter much, if at all. However, that is not true for every file, particularly for system & application files & their enclosing folders. They can be backed up perfectly well on the NAS, but should there ever be a need to restore them, or to restore an entire "snapshot" of the startup drive, you will not get the same set of ACLs as on the backup. This can cause several significant problems, particularly with El Capitan (because of SIP), up to & including preventing the OS from starting up, or apps refusing to launch because their security certificate checksums are wrong.

I don't believe the underlying format is important.

Remember network Time Machine backups use a sparsebundle disk image which hides all the Mac stuff inside a HFS+ format disk image and makes the host format irrelevant.

If you try looking at the Time Machine backup on the NAS itself (most allow this one way or another) then all you will see are the slices of the sparsebundle backup disk image, you will not see its contents i.e. the Mac files themselves.

This has not been my experience with Time Machine to NAS. I must concur with R C-R that eventually usually during a critically required restore that Time Machine suddenly returns with an error saying the file can't be restored. I have run into this now a couple of time with users I help to support.

Besides why would Apple state that Time Machine to any NAS besides Time Capsule is unsupported?

Allan Eckert wrote:

This has not been my experience with Time Machine to NAS. I must concur with R C-R that eventually usually during a critically required restore that Time Machine suddenly returns with an error saying the file can't be restored. I have run into this now a couple of time with users I help to support.

Besides why would Apple state that Time Machine to any NAS besides Time Capsule is unsupported?

Apple are saying it is unsupported because they don't make the NAS products, they did not write the software used on that NAS products and hence have no control over the quality i.e. bug free aspect of such systems. This does not mean it cannot work merely that you cannot blame Apple.

The whole point of disk images (there are a variety of disk image formats) is to provide a way of storing stuff on 'foreign' file systems without risk of damage. Disk image files are used all the time for example on USB memory sticks which most often are FAT32 or NTFS format, they are used on optical discs which most often are High Sierra or ISO 9660 and not inherently HFS formatted.

Another example of using disk images to handle foreign file systems is Virtual Machines. This allows you to create and store for example a Linux EXT3 file system as used by a Linux virtual machine on your Mac! Similarly a Windows virtual machine using NTFS. All despite the fact the Mac itself is using HFS+ and cannot handle EXT3/4 at all itself, and has limited built-in support for NTFS.

Time Machine is not perfect I have had it go wrong with a HFS+ formatted external drive which absolutely is a supported configuration.

There are brands certified or supported?

No, there are not, and if you care about the safety of your data, you won't use any third-party NAS with Time Machine, no matter what the manufacturer says.

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 use 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.)