NeST: Network Storage Technologies Building I/O Appliances on Commodity Systems John Bent, Andrea Arpaci-Dusseau, Remzi Arpaci-Dusseau and Miron Livny com

Outline zIntroduction zCase studies zStorage modules zConclusion

Problem Statement Appliances are attractive because they are robust, reliable, available and especially because they are easy to use. To fulfill these criteria, traditional network appliances impose policy decisions on their users and are built either as kernel modules or upon specially designed kernels. “How to build portable, configurable I/O appliances?”

Goal To create a network-storage “template” that produces a range of I/O appliances according to the storage needs of the target application and any constraints of the host system. Network Storage Technologies Target App Host System Perfect I/O Appliance

Host system constraints zThread support zRaw disk access zSelect interface

Target app. storage needs zInvariant and variant storage needs zInvariant yReliable yLow latency yHigh bandwidth yEasy to administer yCheap

Target app. storage needs zVariant yWrite concurrency yReplacement costs ySecurity and authentication needs yCommunication protocol yTransfer unit

Outline zIntroduction zCase studies zStorage modules zConclusion

Building I/O appliances zFour case studies yReqEx yWiND yWeb proxy cache yCondor checkpoint server

What is ReqEx? ReqEx Staging Area Huge tape library (terabytes) Queue of Reqs Tape Robot A robot moves archived data one tape at a time to a temporary staging area.

Perfect I/O Appliance Condor Manager What is ReqEx? ReqEx Staging Area WAN Compute cluster Data is transferred and stored locally to facilitate access by compute nodes.

ReqEx variant storage needs zWrite concurrency yNo write (or read) concurrency zReplacement costs yTape robot is very slow; objects cannot be lost zSecurity and authentication needs yOnly owner can remove object zProtocol yReqEx can be linked with NeST client library zTransfer unit yWhole object transfers only

What is WiND?

WiND variant storage needs zWrite concurrency yNo write concurrency zReplacement costs yUnknown zSecurity and authentication needs yUnknown zProtocol yPredefined specific WiND protocol zTransfer unit yDisk blocks are accessed directly

What is a web proxy cache? Local Area Network Internet Perfect I/O Appliance Frequently accessed objects can be stored locally to decrease request latencies.

Cache variant storage needs zWrite concurrency yNo write concurrency zReplacement costs yNegligible zSecurity and authentication needs yNone zProtocol yHTTP zTransfer unit yWhole object transfer only

Perfect I/O Appliance What is Condor ckpt server? A condor job runs on an execute machine. Keyboard activity causes the job to be evicted. A snapshot of the process is sent to the checkpoint server. When the job migrates to another idle machine, the checkpoint file is recovered and progress resumes.

CCS variant storage needs zWrite concurrency yNo write concurrency zReplacement costs yThe running time of the job (could be months) zSecurity and authentication needs yUnauthorized access cannot be allowed zProtocol yCan link with NeST client library zTransfer unit yWhole file transfer only I see you’re discussing checkpointing. Don’t forget about incremental.

Outline zIntroduction zCase studies zStorage modules zConclusion

Storage modules Storage Management Concurrency Architectures Data Semantics Static Configuration Protocols Administrative Interface Runtime Adaptation Name Space

Configurable Components zConcurrency architecture zData semantics zProtocol layer zNamespace zSecurity and authentication zStorage management

Concurrency architecture NOB POP POT Easy... but uninteresting. “How can multiple storage requests be interleaved to maximize system throughput?”

Data semantics zMust stored objects be protected from concurrent writes? zIs transaction support necessary? zWhat are the recovery costs for lost objects?

Protocol layer zMost applications can not link with NeST client libraries zMost applications have their own specific communication protocols “How can a protocol layer easily communicate with arbitrary networking protocols?” Tower of Babel

Namespace zFlat zHierarchical “How do clients uniquely identify their stored objects?”

Security and authentication zOwnership zPrivacy zEncryption zAuthentication zAccess rights

Storage management zNative filesystem zRaw disk access zUninteresting from client perspective

Outline zIntroduction zCase studies zStorage modules zConclusion

Conclusions and future work zConclusions yNone zFuture work yLots Maybe you should try a little harder.

Conclusions and future work zHow to most easily identify the variant storage needs of the target application? yConfig file? yInstallation script? yRun-time monitoring? zHow to ensure that performance is at least as good as an appliance specifically designed for the target application?