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AFS/OSD Project

AFS/OSD Project. R.Belloni, L.Giammarino, A.Maslennikov, G.Palumbo, H.Reuter, R.Toebbicke. Contents. Goals of the Project Solution and benefits SCSI T10 OSD Standard Components of the Client/Server Architecture Additional Elements Interactions between Components Client and Server Details

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AFS/OSD Project

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  1. AFS/OSD Project • R.Belloni, L.Giammarino, A.Maslennikov, G.Palumbo, H.Reuter, R.Toebbicke

  2. Contents • Goals of the Project • Solution and benefits • SCSI T10 OSD Standard • Components of the Client/Server Architecture • Additional Elements • Interactions between Components • Client and Server Details • Conclusions and Immediate Goals

  3. Goals of the Project • Principal issues that have to be addressed: • Throughput of a single fileserver is too low • AFS volumes are limited to single disk/lun/filesystem • Large files cannot be striped over the multiple servers • No RW replication Improve AFS performance and scalability

  4. Solution and benefits • File Server will be less loaded • Client requests, security checks, data transfers and platform-dependent object-related meta-data will be handled bydevice servers • Finer-grained performance tuning • Support for object mirroring (RAID-1) & striping (RAID-0) • Better Scalability • Support for location-independent identification of objects Extend AFS to support object-based file management

  5. SCSI T10 OSD Standard • SCSI Object-based Storage Management Standard • OBSD = Object-based Storage Device supporting OSD Standard • Exposes stored data as user objects and partition objects with attributes • Command Descriptor Block (CDB) • Fixed format for specifying commands to execute on OBSDs • Attributes & Capabilities • Meta-data used to describe objects characteristics • Fixed format used by OBSDs for authorization checks • Capabilities can be signed for security reasons (credentials) • Implementation Notice: OBSD access via Rx-protocol • Lightweight, connection-oriented, RPC-based protocol over UDP • Allows for multiple simultaneous connections (seen ~250k)

  6. Client/Server Architecture AFS Client Extended AFS File Server Extended Extended for T10-OSD support Communicates directly with OBSDs Manages data read/write streams Extended for T10-OSD support Tracks objects location Creates Capabilities OBSD Accepts CDBs & parses them Checks capabilities for authorization Executes commands & manages stored objects

  7. Additional Elements • File Descriptor (FD) • Exchanged between File Server and Clients • Describes how files are split into segments composed of objects • Describes segments and objects • Stored where normally AFS file’s data are stored • OSD ID Replicated Databases • Used by File Server to track OBSDs • Use Ubik framework • Security Framework • Used by all components • Makes checksums of capabilities using secret keys to create credentials • Avoids credential forgery and capabilities alteration

  8. Interactions Between Components AFS File Server AFS Client Requests file operation Returns File Descriptor T10-OSD Extension T10-OSD Extension Locate OBSDs Send CDB Read/Write data Create/Remove objects Get/Set secret keys OSD ID DB AFS DB Server OBSD OBSD OBSD OBSD OBSD Min Security Requirements: None Authenticated + encrypted AFS Specific Authenticated

  9. Client and Server Details • AFS Client Extended - Details • Analyzes the status info of the requested file to determine if it uses OSD • Receives/analyzes the FD and contacts OBSDs to read/write objects • Takes advantage of mirroring and striping techniques • AFS File Server Extended - Details • Analyzes a file’s data and meta-data to determine if it uses OSD • Interacts with OSD ID Databases and OBSDs to create new objects based on a policy description file and using a load-balancing algorithm • Creates capabilities, generates credentials and returns the FD to the client • Important Open Issue • T10-OSD is not rich enough to support AFS volume replication and link counts

  10. OBSD Server Details RX-protocol API Network Layer Interface to RX-calls for receiving CDB commands Multi Threaded OSD-CDB API OSD Command Interpreter Interpreter of CDB commands and security enforcer T10-OSD Compliant Logical Unit API Logical Unit Layer Manager of attributes, partitions and user objects Thread Safe File Storage API File Storage Layer Interface to underlying storage technology (Linux FS, Namei...)

  11. Conclusions & Immediate Goals • Provide a basic stable high performance version in August (version 1.0) • Enhance & add features • Support for Mirroring & Striping • Support for other protocols/technologies • Support for AFS volume replication and link counts Still a prototype, but with a working base

  12. References Thank You for your Attention! • AFS/OSD twiki access - currently available upon requestPublic access by August • Andrew File System -http://www.openafs.org • SCSI T10 Technical Committee -http://www.t10.org • RX protocol -http://web.mit.edu/kolya/afs/rx/rx-spec

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