Network File Systems Briefs

Bergwolf@linuxfb.org

3/20/2010

Index

DEC-DAP SUN-NFS AT&T-RFS CMU-AFS CMU-Coda OFS-DCE/DFS Microsoft-CIFS NetApp-Filer EMC-MPFS

Topic-File Storage

Block storage vs. file storage. Block storage: EMC and Hitachi.

Block I/O access Devices may be directly attached (SCSI or Fibre

Channel) or distant accessed (iSCSI or AoE) File storage: NetApp and EMC Celerra.

File I/O access Files and directories are present over the network.

NEC-DAP (Data Access Protocol)

Created in 1976 First wildly used network file system A FAL (File Access Listener) is created on

each data node to serve network-based access requests.

Use local file system to manage local device

RPC war-Sun ONC vs. Apollo NCS

1980s. ONC (Open Network Computing Remote

Procedure Call, now SunRPC). Always in big-endian order.

NCS (Network Computing System) Avoid byte-swap if two peers share a common

endianness.

SUN-NFS (Network File System) Built on top of SUN RPC.

V1: in-house development V2: RFC1904. 1989. First release. Stateless. UDP based.

Without lock management. Big bull authors (including Bill Joy).

V3: RFC1838. 1995. 64-bit support. Asynchronous writes. TCP support. READDIRPLUS operation to get file handle and attributes while scanning dir.

V4: RFC3010 and 3530. Learn from AFS and CIFS. IETF. Performance. Security. Session. Includes a stateful protocol.

NFS semantic: flush on close check return value of close(2) when working with NFS !

SUN-NFSv4.1

pNFS – MPFS Directory delegation and notifications

Clients can have read-only delegated dir. So local cache is enough for any reads.

Server sends change notifications to clients that have delegated dir.

Multi-serve namespace Server replicas to serve requests from clients

AT&T-RFS (Remote File System)

1980s. SVR3 (Unix System V release 3). Bell lab production.

Stateful. Lock management. Complete UNIX/POSIX semantics. Mount devices over network. Digital Equipment, HP and IBM adopted NFS

over RFS.

CMU-AFS (Andrew File System)

1988. Named after Andrew Carnegie and Andrew Mellon. Part of Andrew project.

Kerberos (C/S auth protocol from MIT) for authentication. ACL on dir. Client cache on local file system. Cache consistency—Callback. Server saves all cache

information and sends update notify if file changed. Doesn’t support large shared file updating.

Single file per message in Andrew Message System, vs. single file per mailbox.

Volume. Volume quota. Read-only volume replicas. Shared and local namespace. Predecessor of Transarc, OpenAFS, Arla and Coda.

CMU-Coda

1987. From AFS-2 Client side persistent cache and logged write updates.

Local/global conflicts Server replication, allow all servers to receive write

updates. Server/server conflicts

Extensive repair, both manual and automated. Continued operation during partial network failures. Network bandwidth adaptation.

OFS-DCE/DFS

Open Software Foundation(1988). HP, IBM against SUN and AT&T.

Developed by Transarc, based on AFS. DCE/LFS (Local Journaling file System, aka Episode) as

local cache layer. Improve write performance even over slow network connections.

Filesets management. Transarc bought by IBM. OpenAFS announced by IBM in

2000. DCE/DFS killed by IBM in 2005.

Microsoft-CIFS (Common Internet File System)

AKA SMB (Server Message Block) protocol, originally designed at IBM.

Modified and Merged by Microsoft with LAN Manager product in 1990.

Renamed to CIFS in 1996. Samba – reverse engineering open source implementation. Opportunistic locking.

Batch Locks: client delays sending close request. If a subsequent open request is given, the two cancels each other.

Exclusive Locks: If obtained, client may cache all changes before committing. If others open the same file, server sends revocation notify and client flushes all changes.

Level 2 OpLocks: After revoking a exclusive lock, server may send Level 2 OpLocks to allow client to cache read but exclude write.

Microsoft-CIFS cont.

SMB2 in 2006 (Windows Vista). Specification published. Samba 4 adds support for SMB2. Reduce control messages from over a hundred to

nineteen. Request pipelining: allow sending requests before

response to previous req returns. Compound multiple action in a single request. Larger buffer size and symbolic links. Durable file handle, allows a connection to survive brief

network-outage without having to negotiate a new session.

NetApp-Filer

AKA NetApp Fabric-Attached Storage (FAS). Originally NFS/CIFS based NAS solutions. FTP, TFTP, HTTP, FC (Fiber Channel) and iSCSI are

added later. WAFL (Write Anywhere File Layout).

Read-only and read-write (FlexClone) snapshot. Two directory models (UNIX and Windows) and two file

security models (ACL and bitmask) Consistency points. Automatic fragmentation, saving metadata anywhere

on the disk, usually beside its data blocks.

EMC—MPFS (Multi-Path File System)

More Over

Clustered file system. Shared disk. Translation from file-level ops to block-level must be

done on client nodes. Examples?

Distributed file system. Similar to clustered file systems. Replication and fault tolerance. NFS, CIFS, AFS, Google GFS, etc.

Clustered NAS Stripe data/metadata across the cluster of nodes.

Thank YOU~~

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