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First Time Contributor
Posts: 2
Registered: ‎2009-04-06

Time Machine 2tb limit?

Hi!

I tested the ReadyNAS Pro equipped with 6tb. We (ad agency) are planning to use it with TimeMachine to backup our desktop macs.
I wanted to use the maximum capacity, which is 4607GB, for TM, but despite entering the correct value after submitting the new settings and refreshing I only get something around 2tb (2048 or 2078).

Can anyone help me with that issue?
Occasional Contributor
Posts: 8
Registered: ‎2008-01-07

Re: Time Machine 2tb limit?

Same problem here. ReadyNas NV+ equipped with 4TB and with the latest beta T74.

Even if I max out the capacity it lands on 2TB (2047).

Could someone shed some light on this issue please?
Occasional Contributor
Posts: 5
Registered: ‎2009-04-07

Re: Time Machine 2tb limit?

Erg, purchased a ReadyNAS Pro Business, updated to 4.2.4 and 6x 1.5TB drives. First I did the happy dance. Then I got confused and hit the message boards. Now I'm just frustrated and looks like I'm not the only one.

Backup->TimeMachine says Max:6926, but always resets to 2047GB.

I purchased this setup specifically to give my office one centralized TimeMachine backup location with a capacity larger than what I could get with a flock of Time Capsules. Help?
Esteemed Contributor
Posts: 16,075
Registered: ‎2007-09-24

Re: Time Machine 2tb limit?

2TB is the current limit. The filesystem on the NAS currently has a 2TB per file limit. Same limitation applies to regular files via CIFS/NFS/etc, even iSCSI targets.
Occasional Contributor
Posts: 5
Registered: ‎2009-04-07

Re: Time Machine 2tb limit?

Uh....

That seems like a fairly critical piece of information to share *somewhere* in the docs/howtos/demos. None of the docs I read in all the research I did before making this purchasing decision made ANY mention of this limitation.

Anybody want to take a crack at convincing me to continue to be a customer of Netgear? I've got an office full of mac laptops and this setup I purchased for several thousand dollars is no more useful to me then two time capsules which would have cost a couple hundred dollars.

There's gotta be a work around here. Multiple 2T files/shares? A file for each user/laptop? Use 8K blocks for the ext3 filesystem (instead of the default 4K) for the share so it'll support files > 2T? Use something other than ext3 for the FS?
Esteemed Contributor
Posts: 16,075
Registered: ‎2007-09-24

Re: Time Machine 2tb limit?

RAIDiator 4.2.6 road map is to support 2TB+ volumes for iSCSI/TimeMachine/etc, I don't have a timeframe for that release yet.
Occasional Contributor
Posts: 5
Registered: ‎2009-04-07

Re: Time Machine 2tb limit?

So yeah, I now have 6 of my employees setup with private 400G shares they're each using for Time Machine backups. It's a manual process to get setup and required the root-ssh plugin to get figured out, but shouldn't be too hard to wrap in a tiny shell script. This should allow me to have each employee have a private 400G TM, and use up all 7T in our ReadyNAS when we grow to 14 users ;-)
Respected Contributor
Posts: 971
Registered: ‎2007-12-05

Re: Time Machine 2tb limit?

chirpa wrote:
2TB is the current limit. The filesystem on the NAS currently has a 2TB per file limit. Same limitation applies to regular files via CIFS/NFS/etc, even iSCSI targets.

How is a per-file limit relevant to TM? TM creates sparsebundle packages (a folder) that contain several files as segments representing the entire volume. Therefore, it would stand to reason that any given segment might be limited to 2TB, but how does that translate to the whole sparsebundle?
Contributor
Posts: 98
Registered: ‎2009-02-15

Re: Time Machine 2tb limit?

btaroli wrote:
chirpa wrote:
2TB is the current limit. The filesystem on the NAS currently has a 2TB per file limit. Same limitation applies to regular files via CIFS/NFS/etc, even iSCSI targets.

How is a per-file limit relevant to TM? TM creates sparsebundle packages (a folder) that contain several files as segments representing the entire volume. Therefore, it would stand to reason that any given segment might be limited to 2TB, but how does that translate to the whole sparsebundle?

Just what I was going to say. There is no way the Time Machine sparsebundle can cause file(s) to be bigger than 2TB since the segments are always smaller and are stored as individual files (as far as other operating systems are concerned).

It maybe that the 2TB limit is more an Apple limit in the TimeMachine client software. Since the biggest TimeCapsule is only 1TB and Apple don't ship any Macs with 2TB drives, they may not have thought of this. I wonder if Snow Leopard will address this. (Update - I believe the ReadyNAS is creating the TimeMachine partition as an image on the underlying EXT3 file system, and since EXT3 only allows 'files' up to 2TB in size, this limits the TimeMachine partition also to 2TB.)

For what it's worth, the 2TB limit in the ReadyNAS (for iSCSI for example) is due to the ReadyNAS currently using EXT3 as the underlying file system. See http://en.wikipedia.org/wiki/Comparison_of_file_systems for a comparison of the limits of file systems.

I would guess NetGear are planning on moving to EXT4 although from a Mac point of view ZFS might be a better long term choice since Apple is adding (some) ZFS support in Snow Leopard.

PS. Old though HFS+ might be, it already supports files of nearly 8 Exabytes, way more than even EXT4 which 'only' supports 16 Terabytes. ZFS supports files up to 16 Exabytes. NTFS is not too shabby either, it also supports up to 16 Exabytes. So EXT4 looks a pretty short-term fix.
Respected Contributor
Posts: 971
Registered: ‎2007-12-05

Re: Time Machine 2tb limit?

jelockwood wrote:
btaroli wrote:
chirpa wrote:
2TB is the current limit. The filesystem on the NAS currently has a 2TB per file limit. Same limitation applies to regular files via CIFS/NFS/etc, even iSCSI targets.

How is a per-file limit relevant to TM? TM creates sparsebundle packages (a folder) that contain several files as segments representing the entire volume. Therefore, it would stand to reason that any given segment might be limited to 2TB, but how does that translate to the whole sparsebundle?

I believe the ReadyNAS is creating the TimeMachine partition as an image on the underlying EXT3 file system, and since EXT3 only allows 'files' up to 2TB in size, this limits the TimeMachine partition also to 2TB.)

As far as the filesystem goes, all they actually do is create a directory under /c, such as /c/.timemachine. iSCSI volumes do get created as you describe, though -- a file is created representing the image of the volume.
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