UFS2 with 4TB disk _totally absurd_

Eric Anderson anderson at centtech.com
Fri Apr 7 19:09:48 UTC 2006

Scott Long wrote:
> Eric Anderson wrote:
>> Scott Long wrote:
>>> Ensel Sharon wrote:
>>>>> The FDISK and bsdlabel schemes simply cannot deal with >2TB.  You'll
>>>>> need to either put your filesystem directly on the storage device
>>>>> without and slices/labels, or use GPT to create logical partitions.
>>>> 2TB filesystems are _not large_.  FreeBSD should expect 2-4TB 
>>>> filesystems
>>>> to be in common use in peoples _living rooms_, never mind in the 
>>>> office or
>>>> datacenter.
>>>> So 5.x was a total wash in terms of UFS2 and snapshots, largefiles, 
>>>> etc.,
>>>> 6.0 still doesn't have working filesystem quotas or snapshots, and it
>>>> seems, doesn't support modern (circa 2004) hard drives.
>>>> Maybe a little less time working on FreeBSD 23.0 ... ?
>>> What are you talking about?  UFS2, the filesystem, supports storage
>>> volumes up to 2^63 blocks in size, and filesystems themselves of
>>> more than 2^53 blocks in size.  There is no 2TB limit in UFS2, and I've
>>> personally created filesystems that are indeed much larger than that..
>>> These sizes were supported in 2004, and they are supported in 2006.
>>> What is limited is the FDISK and BSDLABEL formats, which were designed
>>> in the early 80's to handle up to 2^32 blocks.  Neither of these prevent
>>> you from creating a large filesystem.  Maybe you're looking to have a
>>> single large volume to hold both your boot filesystem and your data
>>> filesystem?  That's generally a bad idea since it puts more things into
>>> the path of a failure.  Try doing what most people do, which is to boot
>>> off of a 2 disk mirror (go big and get 500GB disks if you want) and have
>>> your data on a separate array that is more redundant and doesn't need to
>>> use the above partition formats.
>>> Alternatively, find a PC that understands how to boot off of GPT
>>> partitions, and use that format.  It's not FreeBSD's fault that the PC
>>> BIOS uses the FDISK format.  Go complain to IBM and Microsoft for not
>>> having the foresight to future-proof their partition format 25 years
>>> ago.
>> Now if only fsck could be fixed to actually be able to fsck a full 
>> >2TB filesystem with a reasonable amount of memory, without swapping 
>> forever.  Even with journaling, you still need to be able to run fsck 
>> in case of very hard errors.
>> Eric
> Yup, that's a problem.  It's on my TODO list.

Anything I can do to help?

Keep in mind that I have test hardware, including real arrays (6TB 
array, and a 1TB array) available for testing anything.


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

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