FreeBSD and extremely large volumes

[Brooks Davis]

On Fri, May 28, 2004 at 10:03:03AM -0400, Alex Hoff wrote:
> Hi, 
> 
> We have a FreeBSD 4.7 system with an Adaptec 2200S RAID controller and 14 x
> 140 gig IBM drives. We have run in to an issue that when all drives are
> combined into a single volume, the OS can't handle the large number of
> sectors. Since the RAID controller sets the sector size to 512, and we can
> not change that, the total number of sectors in our system is between 2^31
> and 2^32. Well utilities such as fdisk use a signed integer and here in lies
> the problem, the total number of sectors is now negative. Oops. To make
> things worse, as soon as 300 gig drives become available, we will have 14 x
> 300 which will result in the number of sectors > 2^32, thus overflowing the
> int. 
> 
> I am sure that someone else has a setup with such a large amount of storage.
> What have these people done to overcome this limitation? Since we can't
> change the sector size, what other tricks can we use? Keeping the drive as a
> single volume is required for the intended application. 

With 5.x, it's fairly easy to support volumes up to 2TB.  With current
releases you can install on them by creating one small MBR slice to hold
the OS and leaving the rest of the disk unallocated.  Fdisk deals fine
with creating a second slice by hand, but sysinstall has issues.  I
believe there are some patchs to fix sysinstall as well.

2TB is as good as it gets with MBR partition tables.  They simply can't
address any more space.  You either need to move to GPT or place the FS
directly on the disk (allowed with GEOM).

-- Brooks
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