ZVOL

Yes. NexentaStor provides an easy iSCSI and FC target integration which we call "zvol". In fact, many users are finding NexentaStor zvols to be a powerful way to virtualize their storage.

Zvol is an emulated (virtual) block device based on a given appliance's volume. Zvol can be used as additional swap partition but its primary usage is iSCSI and FC. Zvol is a powerful and flexible tool in part because of its tight integration with NexentaStor's storage services; these storage services allow the zvol to be managed, compressed, replicated, have snapshots taken of it and so forth. Being a block device, zvol is effectively a LUN remotely accessible via iSCSI or FC.

Also, zvol can be thin provisioned, and can be grown over time, both in terms of its effective and maximum size. Thin provisioned (also called "sparse") zvol does not allocate its specified maximum size. At creation time thin provisioned zvol actually allocates only a minimum required to store its own metatadata.

You can grow the effective (actually used) size of the zvol by storing more data on it, and the maximum size of the zvol, by incrementing its property called 'volsize'. In NMC, the latter is done via:

nmc$ setup zvol [zvol-name]  property volsize

For very basic usage, zvol has a special property called 'shareiscsi'. This property is manipulated via NMC 'sharezvol' command and/or the corresponding NMV pages. This property assists in the management of the zvols. If you iSCSI-share the very first zvol in the system, you'll create an iSCSI target that backs up the virtual device. This set-up and backup is done automatically, behind the scenes.

Caution: the 'shareiscsi' property is NOT recommended for deployments that require LUN mapping and masking. Please see F.A.Q. article "COMSTAR and sharing zvol via iSCSI" for details.

COMSTAR

Common Multiprotocol SCSI Target (COMSTAR) is introduced in the most recent versions of the appliance. As of the time of this writing, NexentaStor supports two iSCSI target implementations:

1. legacy userspace based target
2. Common Multiprotocol SCSI Target (COMSTAR)
   

Use NMC 'setup iscsi target' command to switch between the two alternative iSCSI target implementations:

nmc$ setup iscsi target

Please make sure to review SCSI Target 2.0 extension for NexentaStor providing LUN mapping functionality, Fibre Channel, and other advanced features. For a consolidated comparison table, please see:

• What are the differences between available NexentaStor SCSI Target configurations?
  

See also related F.A.Q. entries:

• How to optimize iSCSI performance?
• What are the differences between available NexentaStor SCSI Target configurations?
• What is a LU or LUN. How it is different from an iSCSI target?
• Can NexentaStor act as an iSCSI target for VMware ESX?
• I'm using auto-cdp plugin to block-mirror my storage. Initial replication is very slow..
• My appliance exports zvol via legacy iSCSI target. Can it be shared via COMSTAR target?
• Can I use Solid State Drives (SSD) to improve performance?
• I own legacy storage, how can I use NexentaStor with it?

For more information including screen shots and a step by step guide to using this functionality, please see product's User Guide, Section "Using ZVOLs". Or, you can see this text on-line here.