Just discussing NAS's with a friend, and I we are wondering if there is a 16TB limit on a single share in unRAID?

 

The background for asking - some other RAID 5 boxes where some people might like to stuff in 10 2TB drives will be limited to 16TB due to limitations in the EXT3 filesystem. ReiserFS has this same limitation, do I guess this will be a problem for unRAID the day larger-than-16TB drives land on us. But until then, is there any practical limit on a single share ?

Indirectly there is a limit imposed to each disk share. I am not sure how the 'user' fileshare reacts. If the 'user' fileshare isn't used, then you could have MULTIPLE 16 TiB disk shares. That places the current limit to be 20 16 TiB disks.

 

For those that don't know... The limit is imposed by the Reiser Filesystem, which has a max file size of 8 TiB, a max number of files of 2^32 (~4 billion), a max filename length of 4032 bytes, limited to 255 by Linux VFS, and a max volume size of 16 TiB.

 

 

So, does unRAID actually implement the ReiserFS on both the Disk level and on share level ?

 

Does it look likely that the filesystem will be upgraded in the future as larger filesystems become available, perhaps that Reiser4 I read about on wikipedia ?  And in such a case, is it likely that existing arrays could be upgraded without data loss ?

So, does unRAID actually implement the ReiserFS on both the Disk level and on share level ?

 

No, just at the disk level.

So, does unRAID actually implement the ReiserFS on both the Disk level and on share level ?

 

No, just at the disk level.

 

So... Why would there be a 16TB limit on a usershare ?  Do we know for a fact that there is ?

So, does unRAID actually implement the ReiserFS on both the Disk level and on share level ?

 

No, just at the disk level.

 

So... Why would there be a 16TB limit on a usershare ? 

There isn't. 

As mentioned in the second post in this thread, there is a limit on the size of a single file-system on a single "disk" share, but it is far larger than any currently available physical disk.

Do we know for a fact that there is ?

Where did you read there was a limit?

 

Joe L.

Indirectly there is a limit imposed to each disk share. I am not sure how the 'user' fileshare reacts. If the 'user' fileshare isn't used, then you could have MULTIPLE 16 TiB disk shares. That places the current limit to be 20 16 TiB disks.

 

Thanks Joe. Guess I just misinterpreted the above.

 

Indirectly there is a limit imposed to each disk share. I am not sure how the 'user' fileshare reacts. If the 'user' fileshare isn't used, then you could have MULTIPLE 16 TiB disk shares. That places the current limit to be 20 16 TiB disks.

 

Thanks Joe. Guess I just misinterpreted the above.

 

No problem.  The statement is slightly misleading... as there are no 16TB disk drives available to purchase.  In a few years perhaps, but that would be two or three generations of hard disks.  We would need to see 4TB and 8TB disk drives first before a 16TB drive would be sold.

 

The current limit (based on the max size of available physical hard disks) is therefore 20 2TB disks.

OK, just to be crystal clear, if you do have 20 2TB drives could you create one usershare to span all 19 data disks for a total size of 38GB on that single usershare ?

yes, thats whats just been covered if ya read the thread

OK, just to be crystal clear, if you do have 20 2TB drives could you create one usershare to span all 19 data disks for a total size of 38GB on that single usershare ?

Yes... but no single file can span physical disks.  Therefore, you cannot store a single huge 3TB file.  The largest possible single file would be 2TB. 

 

You can store LOTS of smaller files in 38TB though..  That's enough mp3 files to keep you listening from now to forever  , or over 7500 movies at 5Gig each.  ( average 2 hours each + 1 hour break for meals, sleep = 2.5+ years to watch them all... who knows?, by then, 4TB drives might be available.)

 

Joe L.

The reason I listed the limit at 20 16 TiB is because currently

 

[*] unRAID has a 20 drive limit

[*] unRAID uses ReiserFS 3 on each data disk, which has a 16 TiB limit per filesystem

 

So even if a 17 TiB drive was released today, unRAID would only be able to use 16 TiB (per disk). To be able to use more than that (per disk), unRAID requires changes.

 

If the drive limit is raised to 24, then unRAID has an upper maximum limit of 24 * 16 TiB.

 

On a similar note, even if a 17 TiB drive was released today, unRAID would only be able to create a single file that is 8 TiB or smaller. The ReiserFS 3 has a 8 TiB limit per file. To be able to use more than that (per file), unRAID requires changes.

 

The changes required in unRAID would be in supporting a different filesystem other than ReiserFS 3.

 

Here is a vast comparison of the different filesystems: http://en.wikipedia.org/wiki/Comparison_of_file_systems

On a related note, the disk mfg's have product road maps which show 4 TB drives being released at the end of the year. The have 2.5 TB drives scheduled for now-ish, with 3 TB scheduled for early Fall. As with all product roadmaps, everything is likely to change.

Yeah, I find that Harddisk capacity tend to follow moores law although it is not often mentioned. It's been a few years since I looked at statiscics, but from mid nineties to about 2005 they have roughly doubled in capacity every 18 months. Probably holds pretty true for the last few years as well.

 

So, it's always nice to know we can expand the array if 38TB just prooves to be too little in the long run 

 

Thanks for the explanations, every one. I was mostly interested in the user shares, not so much the limits on a single drive which I was already aware of. Guess I shall try and make myself more clear another time.

 

Also, I feel confident I will not run into problems due to the 2TB (or 8TB in the future) limit per file. That would have to be a looong mp3 one heck of a HD movie...  Thanks again.