DataCore's SANsymphony 5.0 headed in the right direction

DataCore's SANsymphony 5.0 headed in the right direction

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DataCore recently announced version 5.0 of its SANsymphony software with additional functionality over the prior version. The functionally introduced is very significant in that it sets a new level of capabilities for in-the-data-path or symmetrical virtualization solutions. The major elements include the ability to dynamically allocate capacity to LUNs that have been defined as maximum size to applications and the incorporation of...

many management capabilities. DataCore is positioning the SANsymphony 5.0 version with its management functions as an "Open Network Storage Management Platform." For ES/OL clients there is a detailed white paper on version 5 in the Software Management section.

Dynamic storage allocation

DataCore has implemented a dynamic storage allocation method with the storage under the domain of the storage domain server where SANsymphony is running. This feature is called Network Managed Volumes (NMVs) and effectively does dynamic capacity provisioning to storage clients. NMVs allow for only the space actually written within a LUN (Logical Unit Number) defined for a client to be allocated to that LUN. Usually a LUN of a specific size is defined for a client (a server connected to the DataCore Storage Domain Server in this case).

The virtualization process used previously by DataCore (and currently by other solutions) will allocate the entire physical space for that LUN across one or more attached storage systems depending on the particular algorithms used. If that LUN was only partially used, the unused space is still allocated and unavailable for other productive purposes. Managing an individual LUN size to be the exact amount required for the data to be stored is an administrative task made difficult by the lack of certainty in application requirements over time. Space that is allocated and not used is wasted.

Using NMVs removes the need for client or storage system based volume management and for tools to automatically extend the size of the LUN. The administration of storage just got much simpler. NMVs also bring capacity utilization to a new level since storage is allocated in small increments as needed from a common storage pool rather than being wasted in the static allocation done by current methods. This sophistication is a significant contributor to the evolution of virtualization and to the next stage of storage management.

Management by storage domains

ANsymphony 5.0, establishes storage domains enabling rules or conditions to manage data. Implementing this policy-based management requires moving away from thinking about the physical storage and its capabilities and toward organizing storage based on the applications and their requirements for storage - storage domains. Storage domains can be managed based on policies for criteria such as quality of service, performance, access privileges, charge-back granularity, and other standard storage management features provided by SANsymphony.

Infrastructure independence

DataCore has introduced independence of underlying connection technology for the virtualization and management capabilities. This allows the decision about management and virtualization to be independent of whether the storage network is implemented over Fibre Channel, Ethernet or other connection technology.

In addition to the support for different connection technologies such as Ethernet and Fibre Channel, DataCore has also qualified connections for external translation products that implement iSCSI and iFCP.

Client-side caching for SCSI

A software driver can be installed on clients (either servers, workstation, or portables) that allows data to be cached on a local disk while I/O is done over the storage network using standard IP connectivity. This SCSI Transport Protocol over IP (STP/IP) brings the features and functions of the managed storage network to systems not normally capable of fully participating due to management and cost concerns. The local disk cache serves as a buffer to provide adequate performance with use of a slow connection network. Standard Ethernet interface cards (NICs) and TCP/IP may be used to provide a means to connect computers running Windows such as servers, workstations or portables that may not have participated in the storage network otherwise. The low cost implementation along with the mitigation of lower performance networks by the client-side caching changes the economics of including additional systems in the storage network.

Client mirroring

DataCore has developed client software that does the mirroring function from the client local disk to the virtual LUNs within the storage network. The Asynchronous IP Mirror (AIM) Client software operates initially on Windows systems and can be used for backup and disaster recovery. Standard IP connectivity provides the network connection for mirroring to storage network resources. With this feature, the economics of allowing remote systems to be mirrored into centrally managed storage has dramatically changed. Even copies of portable computers are viable with the AIM Client software and an IP connection.

Reliability, availability and serviceability

Several additions improve RAS characteristics of the virtualization and management platform:

  • World Wide Name Aliasing establishes an alias for the WWN of the HBA installed on the Storage Domain Server to allow replacement without incurring administrative activity to reestablish the mapping.
  • Integration of UPS controls automatically initiates a cache flush on a power failure event to reduce the recovery time required upon subsequent power on.
  • Write-thru cache management places a failed mirror into a write-thru mode until the mirror is restored.

Performance

DataCore has made several improvements in the performance area:

  • Dynamic load balancing balances I/Os from the storage domain server to the attached storage devices.
  • Adding qualification of the QLogic 2300 HBA supports Fibre Channel 2 Gb technology.
  • Cache support for up to 32 GB for those customers who have very large configurations with many clients attached to the storage domain server has been added.

Management

DataCore has improved the discovery and visualization to provide more information for management of storage in the domain. Other features such as remote copy and point-in-time copy have improved management interfaces as well.

Remote copy

DataCore has improved the Asynchronous IP Mirroring (AIM) feature by adding the ability to make multiple remote copies of the same source volume at different locations with no fixed limit.

Point-in-time copy

SANsymphony 5.0, the optional feature known as Snapshot for making point-in-time copies is integrated with NMVs to substantially reduce the real space necessary to make the copy. Conventionally allocated volumes and NMVs can be either sources or targets for Snapshots. The Snapshot product has also been improved by allowing the snapshot to be done without having to flush the cache first.

Evaluator Group comments:

The announcement by DataCore is very significant. There are some very valuable features/capabilities in the new software release. The most important is the NMVs capability. The ability to dynamically allocate capacity while the operating system and application deal only with a maximum size LUN opens up tremendous new possibilities. Add-in software or special storage systems that can expand the LUN size became unnecessary. Space can now be over-committed because only used space is needed - allocated but unused space is no longer wasted. This will set a new bar for the competition and we expect that eventually all competitors will have to match this function (until then, watch for denials and other obfuscation to buy time for development).

Beyond the valuable features is the overall concept of moving the storage management functionality into a platform. This has been a concept for many vendors so the idea is not new. What is significant is that DataCore is taking steps to deliver on that idea. Eventually, we'll need to see the device management (switches, storage systems, etc.) included to make it a full function management platform. The important thing here is the direction of where this technology is headed.

Again, this is a very significant announcement. It represents a generational improvement or maturing of the virtualization of storage. We expect this to be an incentive for other vendors to be aggressive with their products.

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To view all Storage Evaluator analyses and commentaries, go to Storage Evaluator Tips ===========================================================

The Evaluator Series and Evaluator Series On-Line (ES/OL) are trademarks of Evaluator Group, Inc.


This was first published in February 2002
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