HOWTO: Leopard Time Machine over iSCSI


If you’ve arrived here looking to use iSCSI with Time Machine, I’ve switched to another more robust method. I’ve run into some of the same problems as commenters below, and I’ve become convinced the iSCSI angle is too risky for now.

Open a terminal and run:

defaults write TMShowUnsupportedNetworkVolumes 1

Then you can use a Samba or AppleShare (even Netatalk) server share as a time machine backup location. This works perfectly, as Time Machine creates a disk image with an HFS+ filesystem on which to perform backups, and mounts that.

I’ll leave the original post here for those interested.

Got Leopard? Too cheap/lazy to go get a USB drive for backups? Like taking risks? Etc.

One of the things I was looking forward to in MacOS X 10.5 was Time Machine. To my knowledge, Time Machine was to support two ways of backing up – to a locally connected hard drive, or to a hard drive connected to an AirPort base station. I figured I’d mix it up a little and try centralizing my backup storage to my Linux servers. To do this, I employed iSCSI to connect storage space on the Linux server to the Mac. iSCSI accomplishes this in such a way that MacOS (and any other iSCSI client) sees the disk as a locally connected SCSI disk, and therefore it passes the criteria for Time Machine. You even format it as HFS+ in the normal way when a new disk is connected.

If you have a fileserver capable of delivering iSCSI LUNs, (and if you don’t know what iSCSI LUNs are, go get a USB drive), you can use the globalSAN iSCSI Initiator for OS X to do this with Leopard. They don’t specifically mention compatibility with Leopard, but this has been working for me for several hours now as of the time of this writing.

Caveat emptor: I did hard lock the iMac during a first attempt at an initial backup, but it’s hard to say whether it was iSCSI or one of the myriad other things I was doing at the time. Factor in Leopard being brand spankin’ new, and I can’t say for sure what caused it. If you have a sense of adventure, try this out.

24 responses to “HOWTO: Leopard Time Machine over iSCSI”

  1. I too have tried this same setup. I had complete success backing up 25G from a MacBook Pro over GigE to openfiler (Linux). I let it back up for over a day with no problems.

    However, when trying to stress things a bit on a Mac Pro by copying a 4G file to an HFS+ formatted volume (again from openfiler), it hung after 1 gig or so πŸ™

    I’ve also tried FreeNAS but that never got past 100M or so.

    I tried the copies multiple times – after a reboot πŸ™ – to both openfiler and FreeNAS. I cannot get the 4G file to copy no matter what.

    I would really love for this thing to work. I may submit some traces to the globalSAN guys to see if I can get it worked out.

  2. Thanks for your post.

    I can connect just fine however my machine locks-up every time Time Machine starts the backup. Gets through about 1 GB and freezes my Mac. Linux box is not impacted. Any ideas what could be causing this?

  3. Kirk: Interesting. How much RAM do you have in your Mac? I think your issue may be related to Nick’s – globalSAN may have issues allocating memory in low memory conditions or in cases where the file exceeds a certain buffer size.

    The globalSAN software is still in beta, so I’m hoping they’re actively working on improvements/official word on Leopard support. I’ve had a couple of non-serious issues using it with time machine so far, but nothing major as my home directory / documents folders tend not to contain huge files (those are generally already on my fileservers via other protocols).

  4. 5GB, MacPro 2.66 GHz. Should not be a memory issue. Enabled Data and Header checking and will try some large file transfers to determine if it is a globalSAN to Time Machine issue. Thanks once again for your help.

  5. Same result. No problems with large file transfers at all. Time Machine still freezes the Mac it is running on. If you have any additional ideas regarding Time Machine let me know. Would love to get it working with iSCSI.

  6. I just ran across your blog post while googling for Mac Pro lockups using GlobalSAN. I have openfiler 2.2 setup over a gigabit lan and my Mac Pro 3Ghz machine with 8 GB of RAM will lock up when transferring files to an iSCSI disk on the filer. However, my dual 2 Ghz G5 machine runs the globalSAN initiator connected to the same iSCSI share without issue. I’ve used Time Machine on the G5 and it backs up to the iSCSI disk flawlessly however it’s throughput is much slower than the Mac Pro. When it’s working, I’ve gotten between 35-60 MB/s on the Mac Pro whereas the Dual G5 averages around 10-20 MB/s. Anyone else have any comments? I’m looking for a way to make the Mac Pro reliable when connecting to the iSCSI disk. Maybe when Apple releases their built in iSCSI initiator in Leopard our problems will be gone. I hope so.

  7. Jeff / Kirk: I’ve begun running into the same issues as you both, and have discontinued using globalSAN for now.

    I’ll be continuing to troubleshoot it though, as iSCSI support on the Mac is something I’m interested in from my days of working on storage projects with various employers.

    Food for thought for you guys though, one thing I’m wondering about is the switches. While large file copies and older Macs may place less stress on a regular old network switch, faster Macs or aggressive activities like a Time Machine backup may make the Mac more dependent on SCSI control messaging. If the switch corrupts frames and resends have to take place, this might be exposing bugs in globalSAN.

    I don’t know about you guys but the switches I’m using for my home LAN are pretty low-end. I’m going to try it with some higher end equipment as an experiment.

  8. Brad going with your new suggestion. Works like a charm. Thanks again. I will check your blog for more helpful advice on a regular basis.

  9. Brad,

    I thought about the switch issues too. I almost bought an expensive gigabit switch the other day but couldn’t justify the cost. I have a Summit 24 10/100 switch that is more industrial strength that I’ve thought of testing with. The pity is it’s only 100 Megabit. I guess I’ll give it a go. I do like the fact that you can now use a network drive. Otherwise I guess I’ll put it on hold and wait for the native iSCSI support to appear in Disk Utility. It’s missing from the 10.5.0 release. (I’m totally bummed about that..)

    Giacy, unfortunately that menu pick isn’t in my Disk Utility menu. Apparently it’s a feature that was removed prior to release. I’m wondering if it made it into Leopard Server. Any ideas?

  10. So much for it being the switch. I tried it with the Extreme Networks Summit 24 switch I have and it locked up solid almost instantly. Boy that’s annoying.

  11. Hi all,

    I just want to report that I’m using iscsi/timemachine without any problem.

    I’ve configured my Ubuntu Linux 7.10 Server with iscsi-enterprice-target. I installed Global San’s initiator on my G5. Over Gbit ethernet the transfer speed from server to server is about 20 – 30 mb/s.

    I’m very happy with this setup because all the file management is native mac.

  12. I wanted to report that I succeeded in using iSCSI (on an Openfiler server) with Time Machine via a gigabit link with jumbo packets enabled. The secret to my success? I used the iSCSI initiator from It appears as if the iSCSI initiator from globalSAN is just a plain broke down piece of shit. Well, you do get what you pay for. Oh well. πŸ™‚

  13. Made it work like a champ… global iSCSI + Ubuntu 7.10 + iET + Linux RAID

    I have 30 GB worth of time Machine backup running quite nicely…. Oh.. and since it’s LVM on linux it can snapshot the time machine. Without jumbo Frames I get 100Mb/sec transfer… one Intel Pro100MT NIC and the setup will be Jumbo Frames capable.
    Copied several 6Gb DVD images… works great.

    SMB w/ its locking & Disconnect semantics… SUX.

    There is a REASON the variable is called “UnsupportedNetworkVolumes”…. because they don’t work.

  14. I was thinking of backing up my terabyte of data using Time Machine over iSCSI or another network protocol, but after reading these comments that doesn’t sound like a good idea. However, how Time Machine can back up to a Time Capsule over a wireless network connection without problems? What protocols are in use there? Can’t that be done over a wired connection, or using a different storage product?

  15. in what way wasn’t this reliable? So samba is prefered? Any router with samba share for a connected harddrive will work? I could have got an airport if they hade ONE with sound and disk support at onces, but it’s not like I will buy TWO πŸ˜€

  16. Havent played with iSCSI yet, but on my MBP with 4gb of ram I can backup just fine to an Openfiler 2.3 server SMB share. Wish it had AFP support, but I guess you cant have everything.


  17. For what it is worth (almost 2 years from first post in this thread) I have this (Iscsi) working with FreeNas (0.7 amd64 now) with ZFS. Works a charm and getting up to 300-400Mbs over GigE from G5 iMac, Macbook Pro, Macbook and Mac Mini (Media Center). Local drives can not generate the output speeds that the server can take now. Total backups are about 4TB. No issues to date. My only concern is if I have to do a complete restore from scratch. Not sure how I am going to be able to mount the ISCSI backup drive πŸ˜‰

  18. Can you restore over iSCI?

    i.e. main hard disk dies, i boot off the snow leopard boot disk, and now can i restore the backup?


  19. i can also report that initial impression of my setup of iscsi (gentoo + iscsitarget) based approach seems to be working pretty well. just don’t mount your time machine target simultaneously from two machines like i did at first (=instacorrupt journal and other fun) – forgot it wasn’t a network file system, although it sure feels like one πŸ™‚

  20. @Anandha: afaik os x leopard boot disk doesnt know anything about iSCSI. dont have snow leopard, cant say anything about that. my strategy will be to restore with the help of another mac.