If you want to run any persistent services on your home server, one of the biggest bottleneck is running databases. There are three main issues

  1. Storage size - Raspberry pis have a small SD card that cannot hold all the data you want.
  2. Volume of Read/Writes
  3. Resiliency - How do you RAID the storage attached to your raspberry pi?

It would be nice to have a separate server that can handle storage and let our raspberry pi mount block devices over network. Luckily with Synology NAS, we can achieve this easily.

Steps to achieve storage nirvana

  1. From “SAN Manager” on your Synology NAS, create a new iSCSI target. img.png
  2. Enable node.startup = automatic in /etc/iscsi/iscsid.conf.

Restart iscsi services

systemctl restart iscsid open-iscsi

Discover targets

sudo iscsiadm -m discovery -t sendtargets -p xxx.xxx.xxx.xxx

If you have multiple targets, you will see all the targets listed below. Also, Synology appears to create targets with multiple ip address?. When we login, we should login into the IQN that is against the v4 ip address

sudo iscsiadm -m discovery -t sendtargets -p portalip
XXX.XXX.XXX.XXX:3260,1 iqn.2000-01.com.synology:synology.default-target.9ad11a45432
[2600:1700:7270:7b90:211:32ff:feef:88c1]:3260,1 iqn.2000-01.com.synology:HomeNas.default-target.9ad11a45432
[2600:1700:7270:7b90::44]:3260,1 iqn.2000-01.com.synology:HomeNas.default-target.9ad11a45432
[fe80::211:32ff:feef:88c1]:3260,1 iqn.2000-01.com.synology:HomeNas.default-target.9ad11a45432
XXX.XXX.XXX.XXX:3260,1 iqn.2000-01.com.synology:synology.Target-1.9ad11a45432
[2600:1700:7270:7b90:211:32ff:feef:88c1]:3260,1 iqn.2000-01.com.synology:HomeNas.Target-1.9ad11a45432
[2600:1700:7270:7b90::44]:3260,1 iqn.2000-01.com.synology:HomeNas.Target-1.9ad11a45432
[fe80::211:32ff:feef:88c1]:3260,1 iqn.2000-01.com.synology:HomeNas.Target-1.9ad11a45432
XXX.XXX.XXX.XXX:3260,1 iqn.2000-01.com.synology:synology.Target-11.9ad11a45432
[2600:1700:7270:7b90:211:32ff:feef:88c1]:3260,1 iqn.2000-01.com.synology:HomeNas.Target-11.9ad11a45432
[2600:1700:7270:7b90::44]:3260,1 iqn.2000-01.com.synology:HomeNas.Target-11.9ad11a45432
[fe80::211:32ff:feef:88c1]:3260,1 iqn.2000-01.com.synology:HomeNas.Target-11.9ad11a45432
anirudhan@onefourfive:~$

Out of these, we are only intesrested in the first entry for each targets that are advertised with v4 ip address.

To do that

sudo iscsiadm -m node -T iqn.2000-01.com.synology:HomeNas.default-target.9ad11a45432 -p XXX.XXX.XXX.XXX:3260 --login

You can verify that you have logged in by

sudo iscsiadm -m session -o show

This should list the connection

Attach, Format, and Mounting the device

After logging in, you should be able to see the device in your /proc/partitions

cat /proc/partitions
major minor  #blocks  name

   7        0      50248 loop0
   7        1      60448 loop1
   7        2      60492 loop2
   7        3      94084 loop3
   7        4      50248 loop4
   7        5      94096 loop5
   7        6      44016 loop6
 179        0   31166976 mmcblk0
 179        1     262144 mmcblk0p1
 179        2   30903791 mmcblk0p2
   8        0  314572800 sda

Here sda is the device that we just added.

Format the disk

sudo fdisk /dev/sda

Welcome to fdisk (util-linux 2.34).
Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.

Device does not contain a recognized partition table.
Created a new DOS disklabel with disk identifier 0xee9dcf95.

Command (m for help): g
Created a new GPT disklabel (GUID: EA94CDAF-ACA2-144C-A563-89BE098C8C5D).

Command (m for help): n
Partition number (1-128, default 1):
First sector (2048-629145566, default 2048):
Last sector, +/-sectors or +/-size{K,M,G,T,P} (2048-629145566, default 629145566):

Created a new partition 1 of type 'Linux filesystem' and of size 300 GiB.

Command (m for help): w
The partition table has been altered.
Calling ioctl() to re-read partition table.
Syncing disks.

~$

Do cat /proc/partitions to verify that sda1 is now added to the partitions.

Now make the partitions ext4

sudo mkfs.ext4 /dev/sda1
mke2fs 1.45.5 (07-Jan-2020)
Discarding device blocks:          /78642939
done
Creating filesystem with 78642939 4k blocks and 19660800 inodes
Filesystem UUID: 9bbf47af-b4d2-47ba-89b3-88f7659c05a6
Superblock backups stored on blocks:
	32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208,
	4096000, 7962624, 11239424, 20480000, 23887872, 71663616

Allocating group tables: done
Writing inode tables: done
Creating journal (262144 blocks): done
Writing superblocks and filesystem accounting information: done

~$

To mount this partition automatically

sudo mkdir /data

In your fstab file, add an entry like so

UUID=c4934346-f228-42a4-b16e-3b2f16e8bffc	/data	ext4	rw,users,auto,_netdev	0 0

You can find the uuid by using sudo blkid command.

Troubleshooting

  1. If running sudo systemctl restart iscsid open-iscsi takes a long time, it is mostly because there are pending connections to invalid iSCSI targets. To logout:
       sudo iscsiadm -m node --logout
    To Delete
       sudo iscsiadm -m node -o delete
  2. Incase you are unable to logout because you iscsi is unable to find the session, use this go code from https://github.com/open-iscsi/open-iscsi/issues/228#issuecomment-715770988 to delete the session
     package main

 import (
 "os"
 "fmt"
 "strconv"
 "github.com/u-root/iscsinl"
 )

 func main() {
 ipc, err := iscsinl.ConnectNetlink()

 if err != nil {
 fmt.Printf("Error connecting to netlink: %s\n", err)
 return
 }

 sid, _ := strconv.Atoi(os.Args[1])

 err = ipc.StopConnection(uint32(sid), 0)

 if err != nil {
 fmt.Printf("Error stopping connection: %s\n", err)
 }

 err = ipc.DestroyConnection(uint32(sid), 0)

 if err != nil {
 fmt.Printf("Error destroying connection: %s\n", err)
 }

 err = ipc.DestroySession(uint32(sid))

 if err != nil {
 fmt.Printf("Error destroying session: %s\n", err)
 }
 }

     sudo /home/ubuntu/scsi-delete/scsidelete 3
 2023/01/09 01:35:27 Dumping unexpected event of type 105
 2023/01/09 01:35:27 Dumping unexpected event of type 104

References