The iSCSI initiator first logs on to the target, and only after access is granted by the target, the server can start reading and writing to LUNs assigned to that target. Each iSCSI initiator can have one or more network adapters through which communication is established. As with Fibre Channel environments, you need only to identify the server or cluster that will access the LUN. Starting with NAS software version 4. This is sometimes referred to as LUN carving. Partitions are sections on a logical unit number LUN and provide a way to subdivide the total space available within a LUN.
Partitions are defined automatically when you create a LUN. Note - New components are now configured with LUNs during manufacturing so you must initialize the partition table manually before they can be used.
On the File Volume Operations page, a LUN with a partition table displays a white block, indicating free space, and the value 1 as the number of partitions. A LUN without a partition table displays a blank block and does not display the number of partitions.
When a LUN is first created, all of the available space is allocated to the first partition and any others are empty. To use the space in a partition, you must create a file volume. Each partition can contain only one file volume, though a single file volume can span several partitions.
When you make a file volume, the size of the partition is adjusted to match the size of the file volume and any additional space on the LUN is assigned to the next partition.
After you have made all of the file volumes the operating system supports, any extra space on that LUN is inaccessible. File volumes define the spaces that are available for storing information, and are created from partitions that have available space.
If the volume does not use up all the available space in a partition, the remaining space is allocated into the next partition.
New file volumes are limited to gigabyte in size. To create a larger file volume, you can create and attach up to 63 segments see About Segments to the original file volume. You can increase the size of a file volume by attaching a segment see About Segments. The segment is essentially another file volume with special characteristics.
When you add a segment to an existing volume, there is no distinction between the two and a user sees only more space in the volume. This flexibility enables you to create a file volume and then to expand it as needed without disturbing your users and without forcing them to spread their data over several volumes. As a system administrator adds drives and LUNs, user see more space within the volume. From the user's point of view, the file volume and any directory structures within it are the focus.
If the file volume begins to fill up, the administrator can attach another segment and increase the available space within that file volume. Segments are "volumes" of storage space created much like file volumes.
They can be attached to an existing file volume at any time. Attaching a segment increases the original file volume's total capacity. Each segment must be created independently and then attached to a file volume. After the segment is attached to a file volume, the volume and the segment are inseparable. In general, segments are created as needed and attached to volumes as the volumes begin to fill with data. The main advantage of adding space by attaching segments is that you can create the segment on a new drive or even a new array.
After the segment is attached to the original file volume, the different physical storage locations are invisible to the user. Therefore, space can be added as needed, without bringing down the network to restructure the data storage and create a bigger file volume.
This section provides information about creating the NAS file system. The following subsections are included:. If you are configuring a gateway system, use the storage system configuration tools to create hot-spare drives and logical unit numbers LUNs. Refer to the documentation supplied with the storage system that is connected to your gateway.
For cluster configurations, the LUN limit is shared across both servers, but can be split any way. After you add a new LUN, check the following:. Caution: The zap command reformats the LUN. The disk table will be deleted. When prompted to select the controller unit, use the Controller Unit drop-down menu to select the controller unit that will manage the new LUN.
When prompted to select the physical drives for the LUN same screen as for Step 3 , you can use unassigned drives, or you can select an existing RAID set. If you use unassigned drives, select at least three drives from the graphical image on the right. Each drive image is keyed to indicate whether it is available for use, selected already for LUN membership, empty, and so forth.
Then select the radio button that describes how to proceed:. From the Controller drop-down menu, select the number of the controller to which you want to add a LUN.
Select the drives that will belong to the LUN by clicking each drive image. You must select at least three drives. The drive images show the status of each drive. Note : In a cluster configuration, volume names must be unique across cluster members. You can configure any drive as a hot-spare for NAS appliances.
Click the Add HS button at the bottom of the screen. Select the drive you want by clicking the drive image. The drive images show the status of each drive, as detailed under Add Hot-Spare Window. Make sure the disk you select as a hot-spare is at least as large as the largest disk in any logical unit number LUN defined on the NAS appliance.
This section provides information about creating file volumes or segments. To create a larger file volume, you can add segments to the primary volume. You create one primary volume and then attach up to 63 segments to increase its size.
To create a file volume or segment using the Create File Volumes panel:. If you have recently added new disks to the live system without performing a reboot, click the Scan For New Disks button. The partition number for the file volume in the Partition drop-down menu will increment when the file volume is created.
Type in the name of the new volume or segment in the Name field. The name must begin with a letter of the alphabet a-z, A-Z , and can include up to 12 alphanumeric characters a-z, A-Z, Identical volumes names cause problems in the event of failover. See About Enabling Failover for more information. Select whether the size of the file volume is reported in MB megabytes or GB gigabytes by clicking on the drop-down menu.
The total space available is shown beneath this field. Select the file volume type Primary, Segment, or Raw. If you have the Sun StorageTek Compliance Archiving Software installed, and you want to create a compliance-enabled volume, click Enable in the Compliance section.
Then specify the type of compliance enforcement. Caution: After you enable compliance archiving with mandatory enforcement on a volume, that volume cannot be deleted, be renamed, or have compliance archiving disabled or downgraded to advisory enforcement. If you select Advisory Enforcement, the default retention time will be zero days.
Administrative override is permitted. Note: Decreasing the retention time and removing retained files before the retention period has expired must be performed by the root user from a trusted host. See Managing Trusted Hosts for more information. For more information, see About the Compliance Archiving Option.
Click Apply to create the new file volume or segment. Luckily, unless you're actually setting up the nuts and bolts portion of a new or reconfigured SAN, you shouldn't have to deal with LUNs very often. So what are they and what do they do? It is a virtual address to a device in a SCSI environment. This address tells the system which volume to send and read data from when it's addressed. As mentioned above, a LUN is an address in a SCSI environment that allows one system to find a data store, typically a disk partition, in a larger network.
It's possible to have multiple LUNs on a single physical drive, all pointing at different disk partitions. This level of control allows us to shape our SAN environment to fit our facilities needs.
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