UFS2 and FreeBSD???s apparent 2 terabyte logical volume limit

[Eric Anderson]

Brooks Davis wrote:
> On Mon, Sep 12, 2005 at 10:57:37AM -0700, john wrote:
> 
>>Good afternoon
>>	I seem to have run into a problem with UFS2/gvinum/FreeBSD 
>>	5.4/various disk utilities ??? try as I might I can???t create anything 
>>larger than 2 terabytes. 
>>
>>I think I must be missing something, because I have a hard time believing 
>>FreeBSD still has this limit after going through and fixing the 1 terabyte 
>>limit with UFS1.  Large disks are getting very cheap putting 2 TB in a lot 
>>of people???s hands, so if this hasn???t been fixed until now, does anyone 
>>know of a timetable for when it will be fixed? Is anyone actively working 
>>on this project?  I???d really rather not use Linux, but at least it 
>>supports 2+ TB easily.  What am I doing wrong or what???s the secret? 
> 
> 
> I can't tell what you are missing since you haven't said anything about
> what you've done.
> 
> newfs will work fine, however you need to use something other than
> MS-DOS MBR partition tables or bsdlabels if you wish to partition the
> disk.  GPT should work.  According the the status page, snapshots are
> broken so background fsck apparently isn't an option.  The somewhat
> outdated status page is here:
> 
> http://www.freebsd.org/projects/bigdisk/

I messed with this a few months ago - I think the problem is the actual 
logical disk size.  Anything over 2tb is either not seen by FreeBSD (I 
was using a fiber channel device config'ed to 6tb) or FreeBSD hangs 
detecting it.  I posted about this when I hit the problem.  If you use 
vinum to stripe the 2tb partitions, you can create a large partition 
(greater than 2tb) - I made a 12Tb partition with two arrays, and it 
worked ok, except for a few newfs bumps at the 10Tb mark (I believe). 
The only problem is, fsck requires too much memory at that size to be 
useful (a fullish 2Tb partition takes several Gb memory as it is).

Once UFSJ is complete, it will make this a lot more feasible.

Eric




-- 
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Eric Anderson        Sr. Systems Administrator        Centaur Technology
Anything that works is better than anything that doesn't.
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