Volume management is the process of creating logical units of storage
from physical disk storage. Because these logical storage units are
not bound by the same constraints as physical disk, the system administrator
can use volumes to improve performance and/or reliability. For example,
a single volume may be used to mirror the data on two physical disks.
If one of those physical disks were to fail, the volume management
software would allow uninterrupted access to the data via the remaining
disk in the mirror.
IBM has taken on volume management as many customers require such
services paired with excellent consulting. VM is not an easy topic
to take on as it means that we are looking at how manage our stagage
possibilities. The Enterprise Volume Management System (EVMS) Project
has the goal of providing unparalleled flexibility and extensibility
in managing storage. It represents a new approach to logical volume
management, as the architecture introduces a plug-in model that
allows for easy expansion or customization of various levels of
volume management.
Operating systems manage storage and file volumes on servers by
compressing them, controlling and balancing access. The new volume
management system for Linux will help make Linux capable of managing
more content, files and users, larger servers and at the same time
making it easier to use. With the new volume management technology,
Linux is more capable of supporting the enterprise level business
applications customers need.
The Enterprise Volume Management System (EVMS) version 1.0.0 is
a state-of-the-art, easy to use volume manager of unparalleled flexibility
and expandability. EVMS integrates all aspects of disk, partition,
and volume management into a single, enterprise level design and
implementation, bringing industrial strength features found in proprietary
volume managers to Linux. As a result of the highly modular, plug-in
nature of EVMS, customers will be able to use this technology as
their companies' needs grow and change and as new technologies become
available. EVMS is 100% open source, available for all community
members to use, and is licensed under the GPL.
EVMS technology significantly expands the Volume Management capabilities
found in Linux today by allowing users to access data and manage
volumes from virtually any operating system. In addition, when used
to emulate Volume Managers found in other non-Linux operating systems,
EVMS can help significantly reduce the expense and technical barriers
associated with migrating to a Linux platform.
"EVMS technology is a quantum leap forward in readying Linux
for the enterprise," said Daniel Frye, Director, Linux Technology
Center, IBM. "When adopted in the base, EVMS will make Linux
volume management world-class."
The EVMS project has its home on SourceForge (http://www.sf.net/projects/evms)
and has hundreds of downloads with every release, totaling tens
of thousands of downloads received in less than one year. The community
is very active and has been involved with EVMS since its inception
in January of 2001. Several Linux distributors are currently evaluating
EVMS for inclusion in upcoming releases.
"EVMS technology is an impressive technological step in Linux
storage management, and SuSE welcomes the additional availability
and migration features," said Boris Nalbach, CTO of SuSE Linux
AG. "Such technology will enable all enterprises to take even
more advantage of using Linux for mission critical applications."
"The key to flexible processing power is making it easy to
run Linux in any enterprise environment. And that means making it
easier for enterprises to run their data centers," said Ly-Huong
Pham, CEO of Turbolinux. "Like IBM, Turbolinux has a commitment
to accelerate the penetration of Linux in the enterprise by implementing
features like EVMS in upcoming releases of our Linux operating environments
for enterprise servers and developers. EVMS shows the industry that
Linux provides unprecedented degrees of interoperability and power
at a very low cost."
This inclusive, extensible volume manager utilizes a plug-in system
that supports all volume management capabilities found in Linux
today and is flexible enough to allow for the emulation of volume
managers found in other operating systems and other proprietary
technologies. EVMS version 1.0.0 provides support for multiple disk
partitioning schemes, mirroring (RAID 1), striping with and without
parity (RAID 0, 4, 5), drive linking, bad block relocation, and
volume groups.
A Volume Manager provides a virtual view of local and remote storage.
This virtual view can be used to combine or divide physical storage
in a variety of ways such as combining several physical disks to
appear as one large disk. Additionally, Volume Managers can support
various capabilities such as RAID support, Volume groups, encryption,
compression and much more.
Different volume management implementations use different terms
for their components. Sometimes a term used in one volume management
scheme can mean something different in another volume management
scheme. For example, consider the Multi-Disk (MD) driver, which
implements RAID devices, and the Logical Volume Manager (LVM).
MD takes in disks or devices and exports volumes. A disk can be
any block device, such as a physical disk, a partition, or a volume
exported by MD.
LVM takes in physical volumes (PVs) and exports groups and from
groups it exports logical volumes (LVs). A PV can be any block device,
such as a physical disk, a partition, a volume exported by MD, or
an LV.
As you can see, even between two volume management schemes there
is an inconsistency with terms. Both MD and LVM take in block devices.
MD calls them disks, LVM calls them physical volumes. In either
case it doesn't have to be a disk, nor does it have to come straight
from a physical device. It could be any block device, even a device
exported by MD or by LVM. Both MD and LVM export volumes. In reality,
they export block devices which could result in Linux volumes. An
exported block device could be used as input to another volume manager,
in which case it would not be a Linux volume.
Because of the different terms used to describe the components
in different volume management schemes, we developed a set of terms
specific to EVMS. The terms are intended to describe the various
components of EVMS and not conflict with terms used by other volume
management schemes.
The descriptions of storage objects above hinted at a hierarchy
between the different types. The different types of storage objects
— disks, segments, regions, and EVMS objects — constitute
different layers in the EVMS architecture. The objects in each layer
can be comprised of objects in their own layer or any layer beneath
them.
Disks are at the first layer of the architecture.
The next layer is for segments. Segments can be made from disks
or from other segments.
The third layer comprises regions. Regions can be made from disks,
segments, or other regions.
The fourth layer is for EVMS features. Features can be made from
disks, segments, regions, or other features.
A recent development of storage systems based on WORM have changed
the market and are moving at a high pace:
Many businesses rely on some usage of WORM (write once, read many)
data storage to meet regulatory compliance or simply to add another
layer to their data protection roadmap. This document will discuss
the integration of Network Appliance™ NearStore storage systems
into environments that require WORM data storage.
Why have so many companies implemented WORM data storage given
the myriad of data storage options available? There are two primary
reasons:
Regulatory agencies recognize the ability of WORM data storage
in ensuring the permanence of archived data, and therefore often
stipulate only nonerasable, nonrewritable WORM storage be used for
meeting their regulations.
Many businesses place a premium on protecting certain business records
or critical data files from accidental or intentional alteration
or deletion-and WORM functionality such as non-erasable and nonrewritable
data storage can ensure long-term data permanence.
Most existing WORM implementations are based on older media technology
with limited storage capacity, slow data throughput, and substantial
management overhead. Existing WORM storage options are optical WORM
platters, which each hold about 30GB of data, and WORM tape, with
each cartridge able to store 50GB of data (best case storage numbers
based on latest technology). Traditional WORM storage vendors have
gotten around capacity limitations of individual media by implementing
expensive, complex media library and jukebox solutions that house
numerous media. However, this solution for capacity limitations
creates a problem of ever-increasing management overhead for the
volumes of full media removed from the library or jukebox.
To address issues faced by growing business requirements for WORM
data storage and alleviate issues inherent with traditional WORM
storage solutions, NetApp has introduced SnapLock on its existing
NearStore storage systems. SnapLock allows companies to implement
the data permanence functionality of traditional WORM storage in
an easier-to-manage, faster-access, lower-cost magnetic disk-based
solution. As technology has improved, the lineage for WORM data
storage that started with paper and microfiche progressed to optical,
and has now arrived at a new best-of-breed solution: NetApp®
NearStore configured with SnapLock software for high levels of data
integrity and retention and low TCO (total cost of ownership).
|
Consulting Articles 
