QNAP – Add swap to your NAS for large volume fsck activities

That’s right, another heading from the Department of not terribly catchy blog article titles. I’ve been having a mighty terrible time with one of my QNAP arrays lately. After updating to 4.1.2, I’ve been getting some weird symptoms. For example, every time the NAS reboots, the filesystem is marked as unclean. Worse, it mounts as read-only from time to time. And it seems generally flaky. So I’ve spent the last week trying to evacuate the data with the thought that maybe I can re-initialize it and clear out some of the nasty stuff that’s built up over the last 5 years. Incidentally, while we all like to moan about how slow SATA disks are, try moving a few TB via a USB2 interface. The eSATA seems positively snappy after that.

Of course, QNAP released version 4.1.3 of their platform recently, and a lot of the symptoms I’ve been experiencing have stopped occurring. I’m going to continue down this path though, as I hadn’t experienced these problems on my other QNAP, and just don’t have a good feeling about the state of the filesystem. And you thought that I would be all analytical about it, didn’t you?

In any case, I’ve been running e2fsck on the filesytem fairly frequently, particularly when it goes read-only and I have to stop the services, unmount and remount the volume.

[/] # cd /share/MD0_DATA/
[/share/MD0_DATA] # cd Qmultimedia/    
[/share/MD0_DATA/Qmultimedia] # mkdir temp         
mkdir: Cannot create directory `temp': Read-only file system
[/share/MD0_DATA/Qmultimedia] # cd /
[/] # /etc/init.d/services.sh stop
Stop qpkg service: chmod: /share/MD0_DATA/.qpkg: Read-only file system
Shutting down Download Station: OK
Disable QUSBCam ... 
Shutting down SlimServer... 
Error: Cannot stop, SqueezeboxServer is not running.
WARNING: rc.ssods ERROR: script /opt/ssods4/etc/init.d/K20slimserver failed.
Stopping thttpd-ssods .. OK.
rm: cannot remove `/opt/ssods4/var/run/thttpd-ssods.pid': Read-only file system
WARNING: rc.ssods ERROR: script /opt/ssods4/etc/init.d/K21thttpd-ssods failed.
Shutting down QiTunesAir services: Done
Disable Optware/ipkg
.
Stop service: cloud3p.sh vpn_openvpn.sh vpn_pptp.sh ldap_server.sh antivirus.sh iso_mount.sh qbox.sh qsyncman.sh rsyslog.sh snmp lunportman.sh iscsitrgt.sh twonkymedia.sh init_iTune.sh ImRd.sh crond.sh nvrd.sh StartMediaService.sh bt_scheduler.sh btd.sh mysqld.sh recycled.sh Qthttpd.sh atalk.sh nfs ftp.sh smb.sh versiond.sh .
[/] # umount /dev/md0

 

So then I run e2fsck to check the filesystem. But on a large volume (in this case 8 and a bit TB), it uses a lot of RAM. And invariably runs out of swap space.

[/] # e2fsck /dev/md0
e2fsck 1.41.4 (27-Jan-2009)
/dev/md0: recovering journal
/dev/md0 contains a file system with errors, check forced.
Pass 1: Checking inodes, blocks, and sizes
Error allocating block bitmap (4): Memory allocation failed
e2fsck: aborted

 

So here’s what I did to enable some additional swap on a USB stick (courtesy of a QNAP forum post from RottUlf).

Insert a USB stick with more than 3GB of space. Create a swap file on it.

[/] # dd if=/dev/zero of=/share/external/sdi1/myswapfile bs=1M count=3072

Set it as a swap file.

[/] # mkswap /share/external/sdi1/myswapfile

Enable it as swap for the system.

[/] # swapon /share/external/sdi1/myswapfile

Check it.

[/] # cat /proc/swaps
Filename Type Size Used Priority
/dev/md8 partition 530040 8216 -1
/share/external/sdi1/myswapfile file 3145720 12560 -2

You should then be able to run e2fsck. Note that the example I linked to used e2fsck_64, but this isn’t available on the TS639 Pro II. Once you’ve fixed your filesystem issues, you’ll want to disable the swap file on the stick, remount the volume and restart your services.

[/] # swapoff /share/external/sdi1/myswapfile
[/] # mount /dev/md0
mount: can't find /dev/md0 in /etc/fstab or /etc/mtab

Oh no …

[/] # mount /dev/md0 /share/MD0_DATA/

Yeah, I don’t know what’s going on there either. I’ll report back in a while when I’ve wiped it and started again.