10.1 Understanding Devices

A block storage device is the physical, logical, or virtual storage media available to a server. A device can be directly attached to the server or connected via storage networking protocols such as Fibre Channel and iSCSI.

To manage iSCSI devices on your NetWare server, the server must run iSCSI target software and be the server that you plan to make your iSCSI disk server. For information about managing and using iSCSI devices, see the NW 6.5 SP8: iSCSI 1.1.3 Administration Guide.

10.1.1 Device Size Limit

NSS can recognize physical, logical, or virtual devices up to 2 TB in size (where 1 TB = 2E40 bytes = 1,099,511,627,776 bytes). The restriction for NSS is the size that the device reports to the operating system. If the a device’s size is larger than 2 TB, NSS cannot see the device. You must use the storage vendor’s or third-party disk carving tools to carve the device into logical devices (such as LUNs) that are each up to 2 TB in size.

Different manufacturers report device sizes differently. The actual device size varies with the hardware design and the applications and software drivers that manage the device. Many vendors report sizes using a definition where 1 TB = 10E12 bytes = 1,000,000,000,000 bytes. Space can also be consumed by metadata that is added to manage the device. The location on the device where the metadata is stored can also vary by hardware manufacturer and software vendor. After you format the drive, yet another size might be reported. Third-party product documentation might state the maximum size limits of devices it supports before or after making accommodations for any management data or space lost to formatting. The size of devices you ultimately carve out for use with NSS depends on all these factors.

IMPORTANT:Make sure to refer to the documentation of the device manufacturer, application vendor, and software driver vendor for other limitations on the device size.

If you combine physical partitions or disks to represent a single device to the server, such as for RAIDs, the resulting device must be less than 2 TB in size in order for NSS to see it. For example, if you create a RAID device that is larger than 2 TB in size, NSS cannot recognize the device even if its member devices are each smaller than 2 TB. If the RAID size is larger than 2 TB, you must carve it into multiple LUNs or logical devices of up to 2 TB each in order for NSS to recognize them.

Do not expand devices beyond the 2 TB limit if they contain NSS pools and volumes. On NetWare, the devices are not recognized and you cannot access the data on them. On Linux, devices larger than 2 TB are recognized by the Linux volume manager, but NSS cannot see them.

WARNING:Attempting to expand any of the devices that contribute space to an NSS pool beyond 2 TB in size can result in data loss on the associated NSS pool.

10.1.2 Device Types

The following are examples of common types of devices that are subject to the 2 TB maximum device size:

Server Disks

Server disks include physical disks on the server or logical disks carved from the server disk.

Direct-Attached Storage Devices

Physical or logical disks can be directly attached to the server as individual devices or in a storage array.

LUN Devices

A LUN (logical unit number) can be either a physical or a logic disk drive. NetWare does not differentiate between the two, and all LUNs are treated as physical disk drives. Refer to the iSCSI SAN or Fibre Channel SAN documentation for information about creating and managing LUNs for your SAN implementation.

A metaLUN is a controller-managed group of multiple LUNs or of multiple hardware RAIDs that are striped or concatenated together to be presented as a single LUN device to the server. Refer to the hardware manufacturer’s documentation for information about creating metaLUNs.

iSCSI Devices

An iSCSI device is a remote target disk or tape drive on an iSCSI disk server that is made available across an IP network by iSCSI initiator software running on the server. After connecting to the disk server, you can view the devices in the Devices list and add NSS pools and volumes as you would with any device.

For information about managing and using iSCSI devices on NetWare, see the NW 6.5 SP8: iSCSI 1.1.3 Administration Guide.

For information about managing and using iSCSI devices on OES 2 Linux, see Mass Storage over IP Networks— iSCSI in the SUSE Linux Enterprise Server 10 SP3 Installation and Administration Guide. See also the Linux iSCSI Project.

RAID Devices

A RAID (redundant array of independent disks) is a logical device that combines space from multiple devices by using special hardware, software, or both. Data is striped or replicated across all member devices to improve data reliability, increase I/O performance, or provide device fault tolerance. All RAID types require configuration using a RAID management tool made for the specific hardware or software used in the RAID.

Hardware RAID Devices

In a hardware RAID, the RAID functionality and management are in firmware within the storage cabinet. Refer to the hardware manufacturer’s documentation for information about creating hardware RAIDs.

Controller RAID Devices

Controller RAID devices are also known as BIOS RAIDs, fakeRAIDs, hostRAID, and quasi-hardware RAIDs.

In controller RAIDs, the functionality and management are in the HBA or controller BIOS/firmware. If the controller does not contain an on-board CPU resource to use for RAID management, the controller RAID consumes server CPU resources to manage the RAID.

Refer to the hardware manufacturer’s documentation for information about configuring Controller RAID devices. For information about using Controller RAIDs with OES 2 Linux, see TID 3626577: BIOS RAID Support in the Novell Support Knowledgebase.

Software RAID Devices

Software RAIDs are controlled by special software in the server's OS such as in the HBA driver or in upper level module such as NSS. Software RAIDs consume CPU resources to manage the RAID.

NSS software RAIDs are supported on Linux and NetWare. For information about creating and managing NSS software RAIDs, see Section 13.0, Managing NSS Software RAID Devices.

On Linux, you can optionally use Linux tools to create and manage Linux software RAIDs. Linux software RAIDs must be managed by the EVMS volume manager and have a Cluster Segment Manager or a NetWare Segment Manager on it in order to be visible to NSS. For information about using Linux tools to create Linux software RAIDs on OES 2 Linux, see the SLES 10 SP3: Storage Administration Guide.

Multipath Devices

If there are multiple connection paths between a device’s hardware controller and the server, each path presents a given device to the server as a separate device. You must use a multipath management tool to resolve the multiple apparent devices to a single multipath device. Use the multipath device UUID or alias when you are creating NSS pools and volumes. Multipath tools also provide automatic path management for path failover, failback, and reconfiguration.

On NetWare, the Media Manager multipath I/O service automatically provides multipath resolution and management for devices with multiple connection paths. You can specify priorities for the primary and failover paths to use. For information, see Section 14.0, Managing Multipath I/O to Devices (NetWare).

On Linux, use Linux multipath I/O tools to create the multipath device. Afterwards, you must configure the multipath device to be managed by EVMS and add a Cluster Segment Manager or NetWare Segment Manager on it in order for it to be recognized by NSS. For information, see Managing Multipath I/O for Devices and the SLES 10 SP3: Storage Administration Guide.

Removable Media

Removable media devices include CDs, DVDs, or CD/DVD image files.

On NetWare, removable media are mounted as NSS devices. For information about managing removable media on NetWare, see Section 21.0, Managing Removable Media (NetWare).

On Linux, removable media are mounted as Linux POSIX file systems. Use Linux native tools to manage removable media on Linux.

Virtual Disks

In a Xen virtual environment, you use the Virtual Machine Manager in YaST to allocate storage devices from the host to the virtual machine. The devices that you want to use for the NSS file system on the guest operating system cannot exceed the 2 TB limit, even if the host operating system and guest operating system can handle larger devices. For information about storage considerations in virtual environment, see Section 6.0, Using NSS in a Virtualization Environment.