RE: 12 TB Disk In freebsd AMD 64 ?

[Dan Naumov]

MBR can only work with 2TB volumes, however, we are no longer limited
to MBR. With GPT, we can have really really big volumes. That being
said, I really don't think you should be using a single 12TB volume
with UFS, even if you have underlying redundancy provided by a
hardware raid device. Have you ever had to fsck a 2TB volume or
bigger? It's not fun. My recommendation would be to use ZFS. Use it to
manage your array and filesystems and use it on top of individual raw
disk devices, if you must use your raid controller, use it in JBOD
mode.

If you want a relatively technical introduction to ZFS and why it's
good for you, read up here:
http://www.slideshare.net/relling/zfs-tutorial-usenix-june-2009

- Sincerely,
Dan Naumov
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Re: 12 TB Disk In freebsd AMD 64 ?

[Matthew Seaman]

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On 22/03/2010 14:03:53, Ian Lord wrote:
> I kinda understand freebsd is not well suited for that. I can read
> between the lines that we shouldn't go over 2TB. Is this information
> still exact or outdated ?

Outdated.  The 2TB limit comes from the old-style DOS/fdisk(8) mbr and
bsdlabel(8)[*].  Nowadays you can use gpart(8) instead and set up your
disks using GPT, which doesn't have the same limitations.  Given you're
going to have a separate RAID1 mirror for system disks, you'll be able
to get the machine up and running first, then build the filesystems for
the data partition without having to faff around at install time.

Even though you have a hardware RAID controller, it still might benefit
you to look at ZFS.  You can put a 'zpool disk' on top of a RAID6
created by your hardware, which will let you use all of the available
space easily, and give you various other advantages through the
integrated checksumming etc. built into ZFS.

Cheers,

Matthew

[*] bsdlabel(8) has been modified to allow more than 8 partitions --
the bigdisk article is a bit behind the times there -- but the 32-bit
size limit still applies.


- -- 
Dr Matthew J Seaman MA, D.Phil.   7 Priory Courtyard
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