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How to mount an RPN SAN on Linux

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How to mount an RPN SAN volume on Linux

Published on 10 November 2021

You can mount RPN SAN volumes on Linux machines using Open-iSCSI.

Requirements:

How to install and configure Open-iSCSI

  1. Update the apt package cache and install Open-iSCSI:

    apt update && apt install -y open-iscsi
  2. Open the file /etc/iscsi/iscsid.conf in a text editor:

    nano /etc/iscsi/iscsid.conf
  3. Add the following configuration lines:

    node.conn[0].timeo.noop_out_interval = 0
    node.conn[0].timeo.noop_out_timeout = 0
    node.session.timeo.replacement_timeout = 86400

    The purpose of this modification is to prevent your file system from becoming read-only if the link is interrupted for more than two minutes (by default) between your server and the storage server.

  4. Adjust the setting for automatic reconnection of targets

    node.startup = automatic
    1. Change the following settings to benefit from the data integrity check, if available:
    node.conn[0].iscsi.HeaderDigest = CRC32C,None
    node.conn[0].iscsi.DataDigest = CRC32C,None

How to discover and connect to targets

  1. Run the following command to obtain the list of available targets:

    iscsiadm -m discovery -t sendtargets -p SAN_SERVER
    Note:

    The SAN_SERVER address is displayed in your Dedibox console.

    The target name should look like the following example:

    X.X.X.X:3260,1 iqn.2013-01.net.online:XXXXXXXXXXX
  2. Connect to the target by typing the following command:

    iscsiadm -m node -T iqn.2013-01.net.online:XXXXXXXXXXX --login
  3. Type dmesg to see the kernel logs. You should see some lines like in the following example

    scsi25 : iSCSI Initiator over TCP/IP
    scsi 25:0:0:0: Direct-Access IET VIRTUAL-DISK 0 PQ: 0 ANSI: 4
    sd 25:0:0:0: Attached scsi generic sg4 type 0
    sd 25:0:0:0: [sdd] 2147483648 512-byte logical blocks: (1.09 TB/1.00 TiB)
    sd 25:0:0:0: [sdd] Write Protect is off
    sd 25:0:0:0: [sdd] Mode Sense: 77 00 00 08
    sd 25:0:0:0: [sdd] Write cache: disabled, read cache: enabled, doesn't support DPO or FUA
    sdd: sdd1
    sd 25:0:0:0: [sdd] Attached SCSI disk

    In the example above, the disk detected is sdd, available at /dev/sdd.

    Note:

    The assigned device name may be different, depending on your configuration.

    You can now use your SAN disk like you would any other disk.

Important recommendations for use

As seen in the example above, the disk is available as /dev/sdd. It is not guaranteed that at the next reboot the same drive letter will be used, especially if you add other targets, or if your hardware configuration changes. It is therefore recommended not to use the names /dev/sdX in your configuration files.

How to address devices when using LVM

LVM automatically uses UUIDs to recognize the partitions it uses. In this case, no problems should arise.

How to address devices when using direct disk formatting

Note:

This method is not recommended, because aggregates several RPN SAN storage spaces, and does not allow you to make changes afterwards.

If you format the device or one of its partitions directly, use the link created by the system in /dev/disk/by-uuid/ or the fstab notation UUID=XXX-XXX... for addressing purposes.

How to address devices directly by their UUID

If (unlike LVM) your application does not support the auto-detection of the partitions associated with it via the UUID, it is recommended to use the link in /dev/disk/by-id/.

See Also