4.2.20 : Volume expansion will not work beyond 16 TB...

filesystem expansion with ext4 filesystems is currently limited to original filesystem-size + 8 tb or 16tb total (whatever is reached first).
anything above that will require backup and factory default. this is due to limitation of the ext4 filesystem tools that are used to expand the filesystem.

it is unlikely that there will be a workaround for that anytime soon.

I encountered this issue as well with my Ultra6. I opened a case but managed to resolve the issue as it was taking too much time for me. Please note that the backup and factory reset is the best solution, but for me the offline expansion through ssh login worked. Please realize that this may not work for you, this procedure is at your own risk!.

I did the expansion under 4.2.19 and now have 13,7 TB with a single redundant array (6*3TB Hitachi drives). Starting point was a hot added HDD which successfully was checked and striped. After this the volume was expanded upto 8TB beyond the original size after which a "Volume Expansion Failed" error appeared. I was asked by Netgear support to remove the last added HDD and power down the ReadyNAS after which the HDD should be reinserted and booted. This did not work for me as the "Volume Expansion Failed" error reappeared.

1. First log into the ReadyNAS. For this the ssh addon has to be installed. Use a Linux machine with standard SSH or Putty or similar from a windows machine on the same LAN.

2. Optional:

a. As the filesystem expansion and check commands can be lengthy make sure that your terminal remains connected during the operations. If you want to play it safe use the Linux "screen" command which still may have to be installed:

apt-get install screen

b. Run screen so your session will remain to run even after the ssh session is disconnected:

screen

c. You can detach the session by pressing "CTRL-A" and then "D" and reconnect by typing:

screen -R

2. In order to do an offline expansion no services should be using the volume /c. As I only used SMB and NFS the following commands were sufficient:

/etc/init.d/nfs-kernel-server stop
/etc/init.d/samba stop

3. After this I could unmount volume /dev/c/c/ with the following command. If the command fails something is still using the /c volume. You could check what that is with the lsof command. You may have to disable addons or other services such as AFP, FTP, etc.

umount /c

4. The e2fsck and resize2fs commands use a lot of memory and fail if memory runs out. I increased available memory (my ReadyNAS has only 1GB ram) by making a temporary 1GB swap file. With the "df" command you can check if there is enough room in /root. This was the case for me. If you don't have enough room look for an alternative location. Even an external USB HDD can be used for the swap file.

dd if=/dev/zero of=swap bs=1M count=1000
mkswap swap
swapon swap

5. First check filesystem consistency, I had errors after adding the 5th and 6th drive.

e2fsck -f /dev/c/c

6. Now expand the volume with the following command:

resize2fs -pf /dev/c/c

7. And run another file system check:

e2fsck -f /dev/c/c

8. Mount the volume again:

mount /c

Now I had the full volume size as could be expected. I hope this information is useful.

9. Before I forget it, the swap file should be deleted again :D:

swappoff swap
rm swap

I wonder why readynas does not automatically do an offline expansion upon reboot, if online expansion did not work..

TeknoJnky wrote:
I wonder why readynas does not automatically do an offline expansion upon reboot, if online expansion did not work..

Offline file system expansion take some time. So access to critical data will be unavailable those time. Also it required full data volume file system check before resizing the volume. :)

yes, but I suspect that offline expansion would be preferable to having to do a full backup / factory default / restore process for most people.

even if not automatic, perhaps some way to trigger it via frontview or a 'force offline expansion' addon

Take caution if follow the steps above. The reason we don't support expanding beyond 16TB at the moment, is that (e2progs)resize2fs is not 64-bit clean right now. It doesn't resize properly with 64-bit structures, so when you go to use those new filesystem areas in the future, you will probably hit data corruption.

I agree with the warning for expansion over 16TB. The offline expansion instructions will help you to overcome the 8TB expansion limit, which was my issue. I noticed that a relatively new version of resize2fs is included on the ReadyNAS, however I understand that this tool only reliably expands filesystems over 16TB that where over 16TB at start.

TeknoJnky's suggestion to include offline expansion somehow in the firmware sounds like a good idea to me. It resolves the issue that many people are having with a ReadyNAS when they are faced with the 8TB expansion limit. From experience I can confirm that relying on support to resolve this can be a lengthy affair...

I too would really like to see Netgear provide the option of offline expansion to overcome the 8 TB lifetime expansion limit, if this is at all feasible given the current state of the resize2fs tool. Or, let us know if the command line (with ssh enabled, of course) can be used as a workaround to expand beyond the 8 TB expansion limit. I cannot expand my Ultra 6 Plus volume beyond it's current size of 8.3 GB because another drive will bump in to the 8 TB lifetime expansion limit, since I installed my drives 1 disk at a time when I first started up my system (as the Readynas manual suggested).

If there is a workaround to the 8 TB lifetime expansion limit (other than backup-factory default-restore), I would really like to see it made available or at least documented.

Thanks!!

Hi, if we do this operation,

will the new volume size be considered as the next "start volume size" ?
I mean, if we have the next 8TB expansion limit
it will be applyied to the new volume size ?

thanks

tranas:/var/log/frontview# resize2fs -pf /dev/c/c resize2fs 1.42.3 (14-May-2012) Filesystem at /dev/c/c is mounted on /c; on-line resizing required old_desc_blocks = 1045, new_desc_blocks = 1394 resize2fs: Permission denied to resize filesystem dmesg do EXT4_IOC_RESIZE_FS EXT4-fs warning (device dm-0): ext4_resize_fs:1675: No reserved GDT blocks, can'

can this be fixed. anyone knows what is causing this?