NeST: Network Storage John Bent, Venkateshwaran V Miron Livny, Andrea ArpaciDusseau, Remzi ArpaciDus

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NeST Network StorageJohn Bent, Venkateshwaran
VMiron Livny, Andrea Arpaci-Dusseau, Remzi
Arpaci-Dusseau
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NeST Network storage

• Flexible, commodity based, software-only storage
  appliances
• A storage appliance must be
• easy to deploy
• self-configurable to minimize administrative
  costs
• reliable but also recoverable
• secure against intrusion yet transparent to legit
  users

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From commodity to appliance

• Why build appliance on commodity system?
• Want to ride commodity cost curve
• Avoid high cost of specialized servers (e.g.
  NetApp)
• Leverage high availability of commodity systems
• Allow on-demand acquisition and deployment
• Challenge of building on commodity systems
• Must be portable across multiple operating
  systems
• Additional challenge to achieve high performance
  at user level
• Must be adaptable across a range of storage
  devices

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NeST structure

• Protocol layer
• Pluggable protocols map diverse protocols into
  common control flows
• Analogous to Linux v-nodes
• Transfer layer
• Different concurrency architectures maximize
  system throughput across diverse platforms
• Storage layer
• Provides abstract interface to disks and memory

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NeST Structure
Control Logic
Concurrency Architecture
Pool of processes
Pool of threads
Nonblocking
Storage Layer
Raw disk
Local FS
RAID
Memory
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Many Protocols, Single Server

• Single administrative interface
• Set policies, manage user accounts
• Maintainable S/W
• Shared code base reduces replication, increases
  maintainability
• Different protocols for different purposes
• Grid FTP for wide-area transfers
• Chirp for local-area accesses and reservations
• Single point of control
• - Storage quotas/guarantees can be supported
• - Bandwidth can be controlled QoS provided

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Concurrency architecture

• Three difficult goals
• Low latency
• High bandwidth
• Multiple simultaneous clients
• No single portable solution
• Multiple models provide solutions on a range of
  different platforms
• Multi-threaded
• Multi-process
• Single process event-driven
• Control logic dynamically selects best model

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Storage Layer

• Abstract storage models
• Virtual storage model akin to virtual protocol
  layer
• RAID, JBOD, etc.
• Memory storage model also a possibility
• Provide file system interface to remote memory
• Useful for store and forward buffering systems
  like Kangaroo
• Single interface for storage resource management
• Reservations
• Access control
• User and group management

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NeST, Condor and the Grid

• Wide area scheduling requirements
• Buffers for wide area data movements
• Staging for local replicas of distributed
  datasets
• Guaranteed availability for informed scheduling
• Flexible/dynamic management of user accounts
• Example

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1) Reserve space at NeST 2) Initiate transfer
from distributed repository 3) Schedule jobs at
local cluster. 4) Jobs access data locally.
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Distributed repository
Local NeST
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Future work

• HTTP administrative interface
• Define metrics by which to measure
• Deployability
• Manageability
• Reliability
• Allow reservations to have a cost
• Provide mechanisms by which files can have
  arbitrary, searchable metadata