REDSPHERE GLOBAL - STORAGE DEFINED:

THE BASIC STORAGE GUIDE

Getting started in the world of backup and recovery can be tedious to say the least. Equipment, personnel, effectiveness and cost efficiency are most likely a priority when exploring the various solutions offered.

This is why we at Redsphere have attempted to provide the necessary information when exploring solution options. Below is a list of terms that will be useful when determinin the types of solutions needed. If there is a term that you are interested in and it is not on this or subsequent pages please contact us so we can add the information you are interested in.

For additional information or comments please inquire here...

TYPES OF STORAGE

Primary Storage - storage immediately utilized by the server.

• Memory
• Processor
• Cache

Secondary Storage - storage that is local to the server.

• Optical (Hard disks)
• CD-RW / DVD-RW
• Tape

Near-Line Storage - storage external to the server(s) but resides on-site.

• Tape
• Optical
• CD-RW / DVD-RW

Offline Storage - storage external to the server(s) and resides off-site. A good example would be a Disaster and Recovery Site.

• Tape
• Optical
CD-RW / DVD-RW
• Memory sticks

STORAGE TERMS / PROPERTIES

Volatility

• Storage remains only when power is applied. When power is removed the information is lost. Namely primary storage items.
• Example - RAM (Random Access Memory)

Non-Volatility

• Storage will remain when there is no power applied. Secondary storage items
• Example - Hard disk

Random Access

• Data can be accessed at any moment and is a quick way to retrieve data.

Sequential Access

• Data needs to be found on the device by searching the contents. This is your typical hard drive or tape drive.

Data Compression

• Software

• A computer program compresses the data.
• This can be processor intensive and slower that hardware compression.

• Hardware

• The hardware compresses the data.
• This is typically faster than software.
• Most tape devices and some HBAs (Host Bus Adapters) have this functionality.

Throughput

• Traditionally the speed from the host controller to the storage device.
• In storage terms this typically Megabytes per second (MBps).

TYPES OF NETWORKS FOR STORAGE

DAS - Direct Attached Storage

• Storage is directly connected to the server - Managed by a single host
• Traditional storage implementation
• Devices are attached to the server bus

• Pro - Inexpensive hardware
• Pro - Most administrators are familiar and know how to use SCSI based storage
• Pro - Mature technology (SCSI)
• Con - Adding more storage requires adding more servers
• Con - Not routable
• Con - Monitoring and allocating storage can be time consuming
• Con - Other servers must access storage through the single host

NAS - Network Attached Storage

• Connecting multiple servers to a single storage pool (disk or tape)
• IP / Network Driven (LAN)
• Host independent file system

• Pro - Priced competitively
• Pro - Easier to add storage (Management costs)
• Pro - Ability to provide several terabytes of storage
• Pro - Accessiblity to multiple resources
• Pro - Accessiblity to multiple operating systems
• Con - Could bottleneck the LAN
• Con - Optimized for file level storage
• Con - Does not support block level storage

SAN - Storage Area Network

• Physically seperates the servers from the storage devices
• Servers and storage devices are connected to a dedicated network
• Any servers can be configured to access any storage array
• Allows for block level storage

• Pro - Allows servers and storage to scale independently
• Pro - SAN does not compete with the LAN
• Pro - Access to storage is affected by a failure of a single server
• Pro - High ROI for larger implementations
• Con - Initial investment can be high
• Con - Larger SAN can provide management challenges
• Con - Personnel must be trained
• Con - Fibre Channel is not as mature as Ethernet or SCSI

CAS - Content Addressable Storage

• Appliances that eleminate duplication of fixed content files
• CAS is a fairly new technology
• CAS is not a storage transport but a information access architecture
• Example - You send an email to the entire company that contains 5,000 recipients. With the existing deduplication technology utilizing a CAS applience the storage device only saves one copy of the 5,000 emails and uses pointers (tags) when the email is referenced by users.

• Pro - Drastically reduces the storage space need for fixed content files that exist in duplicates
• Pro - Keeps hardware costs down by condensing the storage
• Con - New tecnology
• Con - Fairly expensive due to the maturity of the product

DEVICES

SCSI Devices

• Hard drives, tape drives, other peripheral devices
• Either 8 or 16 devices depending on the interface
• Bus length Low Voltage Differential (LVD) = 12m
• Bus Speed < 320 MBps (Ultra 320)

iSCSI Devices

• iSCSI controllers are needed to control iSCSI devices
• IP based
• Gigabit Ethernet
• Relatively affordable compared to SCSI and Fibre Channel

Fibre Channel Devices

• Fibre channel controllers are needed to control fibre channel devices
• Tape drives, optical devices, switches, other periperals
• Distance <= 10 Km
• Transfer Rate <= 400 Mbps (4Gbs ports)

OPTICAL (X-ATA)

Serial ATA (S - ATA)

• Hot pluggable
• TransferRate <= 300 MBps

ATA (P - ATA)

• Parallel ATA
• Traditional ATA drive found with most legacy PCs. This has the 40 pin ribbon cable connector.
• Transfer Rate <= 133 MBps

“I am prepared for the worst but hope for the best”
- Benjamin Disraeli