02 direct attached storage
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storeage pptTRANSCRIPT
© 2006 EMC Corporation. All rights reserved.
Direct Attached Storage (DAS)Direct Attached Storage (DAS)
Module 3.1
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Direct Attached Storage (DAS)
After completing this module you will be able to:
Discuss the benefits of DAS based storage strategy
Describe the elements of DAS
Describe the connectivity options for DAS
Discuss DAS management considerations
Identify the best environments for DAS solutions
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What is DAS?
Internal External Direct Connect
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DAS Benefits
Ideal for local data provisioning
Quick deployment for small environments
Simple to deploy in simple configurations
Reliability
Low capital expense
Low complexity
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Physical Elements of DAS
CPU
Motherboard
Clustered group of processors
Processor cards
Complete system
Internal
External
Hard disk(s)
CD-ROM drive
Optical drive
Removable media
Tape devices/tape library
RAID/intelligent array(s)
Portable media drives
Connectivity
Storage
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DAS Connectivity
Block-Level Access Protocols:
ATA (IDE) and SATA– Primarily for internal bus
SCSI– Parallel (primarily for internal bus)– Serial (external bus)
Buss and Tag – Primarily for external mainframe– Precursor to ESCON and FICON
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DAS Connectivity: Internal
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Internal DAS Connectivity Examples
Parallel Connectivity Cables
34-wire floppy cable
80-wire IDE cable
50-wire SCSI-2 cable
Serial ATA cable
Serial Connectivity Cable
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DAS Connectivity: External
Host Storage Device
External DAS
HBAHBA
Example of an external connectivity cable
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DAS Management: Internal
Host provides:– Disk partitioning (Volume management)
– File system layout
– Data addressing
Direct Attached Storage managed individually through the server and the OS
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DAS Management: External
Array based management
Availability – multi-path I/O
Lower TCO for managing data and storage Infrastructure
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DAS Performance Considerations
Factors to be considered for DAS performance:
• Hard disks
• Memory cache
• Virtual memory (paging)
• Storage controllers• Protocol supported (e.g. SCSI, FireWire, USB, etc.)
• RAID level
• Bus
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Internal DAS Application Example
Hard Drive
40 Pin Ribbon Cable
Motherboard
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External DAS Application Example
ESCON HBACable for
external DAS connectivity
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DAS Challenges
Hosts must be directly connected
Data availability
Data slowdowns possible– CPU congestion, caching, multi-pathing
Scalability is limited– Number of connectivity ports to hosts
– Number of addressable disks
– Distance limitations
Downtime required for maintenance
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Module Summary
Key points covered in this module:
DAS can be:– An integrated part of the host computer
– Directly connected to a single server
DAS is made up of a CPU, connectivity, and storage devices – There are several options within each of these categories
DAS connectivity uses block-level access protocols
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Check Your Knowledge
What are the physical elements of DAS?
Give an example of when DAS is a good solution.
Describe internal DAS connectivity.
Describe external DAS connectivity.
What are some areas that you need to consider as part of DAS management?