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Storage and Availability Management

Showing posts tagged with Storage Foundation
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Ameya | 03 Aug 2007 | 1 comment
Array Policy Module (APM)


The APM framework was introduced in Volume Manager 4.0 release. The 4.0 release brought about a major change in DMP architecture - the introduction of APM. As the name suggests, the Array Policy Module (APM) is specific to an array type and defines the policies for an array type. Analogous to its Array Support Library (ASL) counterpart in user space which enables the DDL to identify the array completely, the APM enables DMP kernel to perform array specific operations such as failover, NDU (Non-Disruptive Upgrade), STPG (Set Target Port Groups) and even an I/O policy.

The APM makes it possible for DMP to dynamically add kernel support for an array. The support for enabling an APM is completely online and does not require a reboot. An APM is essentially a dynamically loadable kernel module that is validated and loaded by DMP whenever DMP detects the array type support exported by that APM. In other words, the DDL...

charmer | 17 Jul 2007 | 7 comments
Some engineers at Sun promoting ZFS have been publishing comparisons between VxFS and ZFS that are rather unflattering to VxFS. You can read the most recent white papers they've published comparing ZFS with VxFS, ext3, and Window's NTFS as well as some blog entries comparing the performance of VxFS and ZFS.

The comparisons with VxFS appear to be objective, but in fact the performance comparisons are chosen quite selectively. In addition, the most recent white paper contains a few significant errors.

Going through the most recent white paper from beginning to end, the first thing to strike me were some significant errors in the discussion of file...

Mandar Bhide | 18 Jun 2007 | 0 comments
Storage capacity requirements are growing at an explosive rate, complicating data and storage management in mission-critical and compliance-driven environments. Enterprises need to securely store more information and more information types. Data must be safely secured and available for rapid recovery in the near term, while also meeting long-term archival and compliance regulations. These complex issues have created a variety of manageability, storage availability and price performance challenges, ranging from missed service levels to operational risks.
Recent industry trend reports by analysts show that the IT budgets are growing at six percent a year; but data under management is growing between 50 and 70 percent or more. Keeping up with data growth while reducing the cost of data management, requires deep analysis and an understanding of underlying storage delivery infrastructure.
To ensure the financial benefits...
Ameya | 13 Apr 2007 | 1 comment

The first basic function for a multi path (MP) driver is to identify the set of block devices that can be supported. The device discovery is generally triggered when the MP driver is loaded into the operating system (OS) as part of boot process. During early boot, not all devices connected to the system may be available. For example, the devices connected using the fibre channel (FC) cables may not be available during early boot time unless there is special support from the bootstrap, which is usually from NVRAM or EEPROM, to identify the fibre channel devices. In any case, it may be required for a MP driver to rescan the OS device tree at a later stage of boot process.

One of the biggest challenges in device discovery is the ability and skill of MP driver to discover disk devices and their attributes in a non-intrusive fashion such that the disk media is not touched. In other words, the device discovery has to be purely read-only operations to identify the disk and disk...

Ameya | 02 Apr 2007 | 0 comments

The Dynamic Multi Path (DMP) capability was first introduced in Volume Manager 2.5.7 release primarily to support A/A multi path arrays from Sun Microsystems. In those days, the early version of arrays had SCSI connections with fat and thick cables running from host to the array directly. Unlike the present day modern arrays, there was no concept of fabric switches, and no fiber channel (FC) technology enabled on the arrays. The first DMP could do only multi path operations such as load balancing using balanced path I/O policy, path failures and restoration by using SCSI inquiry commands. Since the number of devices were handful, the error processing and restore processing were all single threaded tasks. Further, as the number of supported arrays was small, the entire device discovery and reconfiguration was closely tied to the parent operating system.

The next major enhancements of DMP were introduced in Volume Manager 3.1.1 release that had support to co-exist with...

The STN Guy | 22 Mar 2007 | 0 comments

Welcome to the Veritas Storage Management technical blog.  My name is Rob Soderbery and I run the Storage Management Group at Symantec, leading a team of engineers developing the Storage Foundation and CommandCentral Storage product lines. This forum is designed to feature ideas, opinions and solutions from the technical community within the Storage Management Group.  You will hear in this blog from a variety of contributors, including architects, engineers and product managers all looking to provide you with information you may find helpful.   Many of the users I speak with are wrestling with thorny storage and data management problems.  Just this week I spoke with a leading electronic banking firm looking at how to transform their storage environment.   I had a chance to speak with the storage management team leader, the server architecture leader as well as their boss -- the...