switching backup devices

The sparc backup server from 2005 was up for a replacement. It was too noisy and too power hungry to keep it running, so it was turned off most of the time anyway. I decided yesterday to replace it with a qnap TS-412, but I wanted to keep the four sata disks, and preferably also the data.

One problem is that there is no way for four RAID5 configured disks to insert them into the qnap without them being "initialized" (as in completely erased losing all data).

First I wanted to be sure all four disks where still operational, which I couldn't do as long as the adaptec controller was in the sparc computer, so I had to move everything to an (already full) x86 machine... or not ?

Being a Linux user, I am generally lazy, so I figured it also had to work if I just moved the controller to the x86, leaving the disks in the sparc... not without risks:

1. the 64-bit pci card had to work in a 32-bit pci slot. Some don't... luckily this one did! The picture below shows the Adaptec controller in the x86 on the right, with the sata cables going through the back of the sparc to the four disks.

2. What to power on first, the x86 or the sparc ? Can something break if only the controller, or if only the disks have power ? I pressed both buttons simultaneously... was I lucky that it worked, or is this normal ?

3. The fricking sparc blade 1000 cover has to be shut tight for the sparc to actually power on. Note also the lack of any cables on the x86 (the left), except for the cat5. This computer has been working without keyboard or display since 2003... why bother when ssh and ssh -X can do everything!

4. Will the x86 (running debian) still come up when I add an extra scsi controller? Note that this x86 was installed with Debian ten years ago, and since then upgraded to $currentDebianToyStoryCharacter. It did make the RAID5 appear as /dev/sda, but thanks the UUID= in /etc/fstab it all worked fine!

root@barry:~# fdisk -l 2>/dev/null | grep Disk
Disk /dev/sda: 960.0 GB, 959994396672 bytes
Disk /dev/sdb: 60.0 GB, 60022480896 bytes
Disk /dev/sdd: 200.0 GB, 200049647616 bytes
Disk /dev/sdc: 82.0 GB, 81964302336 bytes

Everything worked, data was copied, disks inserted in the qnap and reformatted and all is up and running.

iSCSI mini howto

Some things in life, like iSCSI, are simple!
iSCSI is a protocol that allows you to have SCSI over IP.

The iSCSI Target

The host containing the physical hardware is called the iSCSI target and is easy to setup on Linux using iscsitarget.

aptitude install iscsitarget
aptitude install iscsitarget-dkms (Debian 6)

After enabling it in /etc/default/iscsitarget you can use files, hd devices, partitions, lvm volumes or software raid mdadm devices as 'physical hardware disks'

root@debby6:/etc/iet# cat ietd.conf
Target iqn.2010-02.be.linux-training:storage.lun1
IncomingUser isuser hunter2
OutgoingUser
Lun 0 Path=/iscsi/lun1.img,Type=fileio
Alias LUN1

Where /iscsi/lun1.img is a zeroed file created with

dd if=/dev/zero of=/iscsi/lun1.img count= bs=

Add the device to the allowed list:

root@debby6:/etc/iet# cat initiators.allow
iqn.2010-02.be.linux-training:storage.lun1

and start the server. You should see this:

root@debby6:/etc/iet# cat /proc/net/iet/session
tid:1 name:iqn.2010-02.be.linux-training:storage.lun1

The iSCSI Initiator

The host that connects to this target server is called the Initiator. Most Linux distros have this available as open-iscsi.

aptitude install open-iscsi

A discovery will show available devices on the target:

root@ubu1104:/etc/iscsi# iscsiadm -m discovery -t st -p debby6
192.168.1.31:3260,1 iqn.2010-02.be.linux-training:storage.lun2

Configuration with chap user and password takes a couple of commands:

root@ubu1104:/etc/iscsi# iscsiadm -m node --targetname "iqn.2010-02.be.linux-training:storage.lun1" --portal "debby6:3260" --op=update --name node.session.auth.authmethod --value=CHAP
root@ubu1104:/etc/iscsi# iscsiadm -m node --targetname "iqn.2010-02.be.linux-training:storage.lun1" --portal "debby6:3260" --op=update --name node.session.auth.username --value=isuser
root@ubu1104:/etc/iscsi# iscsiadm -m node --targetname "iqn.2010-02.be.linux-training:storage.lun1" --portal "debby6:3260" --op=update --name node.session.auth.password --value=hunter2

That's it! Now (re)start the open-iscsi service and use fdisk to see your iSCSI device.