help with xfs expansion

[A Hired Goon]

Greetings,

I plan to expand my current raid setup but have found out that fdisk partitions have a 2tb limit. My current filesystem setup is xfs on a single partition (the whole disk at 2tb currently).

What I would like to do is one of the following:

Either migrate from using fdisk partitions to using the gnu parted partition system so I can creat >2tb partitions

or

move to the XFS system to use /dev/sda instead of /dev/sda1 and not worry about partitions affecting my expansion.




Anyone have experience with either of these? I am thinking the fdisk->parted may work if the parted partition setup does not use any more space then the current partition table does (keeps the xfs superblock in the same location).


Mentioning superblock, switching from /dev/sda1 to /dev/sda should invlove moving said superblock to the start of the disk from the start of the partition correct? is this possible without dataloss?



I think my only alternative would be multiple 2tb partitions. workable, but not preferred.


if anyone can offer some help/advice on this it would be uch appreciated

thanks

AHG

[Rikai]

I'm not sure about moving XFS superblocks, but I would be very hesitant to play with that without a full backup first.

Are you doubling the amount of storage? Or at least adding enough to cover the amount of data you already have? If so, you might take this opportunity to migrate to an LVM-type setup, which is much more flexible than relying on partition tables. On the storage you are adding, you could set up logical volume(s), copy the data over, and then convert the 2TB of space into physical volumes for LVM, add them to your volume group, then extend your logical volumes as needed and grow your XFS filesystem to a larger size. Since you need to copy 2TB of data to new partitions, this will take a while, but moving to a logical volume manager will leave you in a better situation for the future when you need to upgrade or otherwise change your storage.

Wikipedia article on Logical Volume Management
Gentoo guide to LVM2

To break it down, you'd need to:

Add your storage, and initialize it as a PV
Create a volume group using your new PVs
Create a logical volume on your new VG, large enough to hold your old data
Create an XFS filesystem on this new LV
Move your data from your old FS onto this new FS
Check check check that everything copied successfully, permissions are right, etc
Wipe out the old storage, and reintialize it as a PV
Add this PV to your VG
Extend your LV to take over the new space
Grow your FS to fill the now larger volume

It's a bit of work (and moving all that data would surely be nailbiting), but if you ever need to add more space in the future or upgrade disks, it will be much, much easier. There are other cool features of LVM you might be able to take advantage of (snapshots, etc) depending on your situation.

[A Hired Goon]

The current setup is 6 500GB drives setup with raid 6 exported via iscsi. The data is just a single directory of large files, nothing fancy like a root disk or anything. I had previously setup a couple 300GB drives in a linear LVM setup a year ago, but never thought of using it for this setup. I will definetly have a look at the info as it would offer some interesting expansion options beyond my original plans for this raid.


Although Im hesitant on having to buy 6 drives to move the data to a better setup, it may end up being the solution if I am unable to find another way. I have been checkin the prices on the WD RE drives and hopefully they will drop more soon.


thanks for the links and info rikai

AHG