Mirror File System A Multiple Server File System John Wong CTO - - PowerPoint PPT Presentation

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Mirror File System A Multiple Server File System John Wong CTO - - PowerPoint PPT Presentation

Nov 05, 2023 901 likes •1.24k views

Mirror File System A Multiple Server File System John Wong CTO John.Wong@TwinPeakSoft.com Twin Peaks Software Inc. Page 1 of Multiple Server File System Conventional File System EXT3/UFS and NFS Manage files on a single server

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John Wong

CTO

John.Wong@TwinPeakSoft.com

Twin Peaks Software Inc.

Mirror File System

A Multiple Server File System

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Multiple Server File System

  • Conventional File System – EXT3/UFS

and NFS

– Manage files on a single server and its storage

devices

  • Multiple Server File system

– Manage files on multiple servers and their

storage devices

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Problems

  • Single resource is vulnerable
  • Redundancy provides a safety net

– Disk level

=> RAID

– Storage level

=> Storage Replication

– TCP/IP level

=> SNDR

– File System level

=> CFS, MFS

– System level

=> Clustering system

– Application

=> Database

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Why MFS?

  • Many advantages over existing

technologies

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Local File System

Data

EXT3

Application 1 Application 2

Kernel Space User Space

Disk Driver

EXT3 manages file on the local server’s storage devices

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Application Application

NFS (Client mount)

Application Application Data

EXT3/UFS NFSD

Network File System

Client Server

NFS manages file on remote server’s storage devices

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rsync, tar

NFS (Client mount) Application Application Data B

EXT3/UFS

NFSD

EXT3 | NFS

EXT3/UFS

Data B

Client Server

Application

Applications can only use either one, not both.

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  • Combine these two file systems to manage file on

both local and remote servers storage devices

  • - at the same time
  • - in real time

EXT3 + NFS ??

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Application Application Data EXT3/UFS Application Application Data EXT3/UFS

Passive MFS Server

MFS = EXT3 + NFS

Active MFS Server MFS

NFS

User Space Kernel Space

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  • MFS is a kernel loadable module
  • loaded on top of EXT3/UFS and NFS
  • Standard VFS interface
  • Provide Complete Transparency
  • to users and applications
  • to underlining file systems

Building Block Approach

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Q & A

Application Application Data A Application Application Data B

MFS MFS

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  • Building block approach
  • - Building upon existing EXT3, NFS, NTFS, CIFS

infrastructures

  • No metadata is replicated
  • - Superblock, Cylinder group, file allocation map

are not replicated.

  • Every file write operation is checked by file system
  • - file consistency, integrity
  • Live file, not raw data replication
  • - The primary and backup copy both are live files

Advantages

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  • Interoperability
  • - Two nodes can be different systems
  • - Storage systems can be different
  • Small granularity
  • - Directory level, not entire file system
  • One to many or many to one replication

Advantages

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  • Fast replication
  • - Replication in Kernel file system module
  • Immediate failover
  • - No need to fsck and mount operation
  • Geographically dispersed clustering
  • - Two nodes can be separated by hundreds of miles
  • Easy to deploy and manage
  • - Only one copy of MFS running on primary server is

needed for replication

Advantages

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Why MFS?

  • Better Data Protection
  • Better Disaster Recovery
  • Better RAS
  • Better Scalability
  • Better Performance
  • Better Resources Utilization
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File System Framework

SOLARIS Internal, Core Kernel Architecture, Jim Mauro. Richard McDougall, PRENTICE HALL

Optical drive Network

File System Operation calls

User Applications

System Call Interface

File Operation System Calls Other System calls

read () write ()

  • pen ()

c l

  • s

e ( ) mkdir () rmdir () link () ioctl () creat () lseek () mount () umount () Statfs() sync () Vnode interfaces VFS interfaces UFS (2) NFS (2) VxFS HSFS QFS UFS (1) NFS (1) PCFS

PCFS

Data Data Data Data

File System Operation calls

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MFS Framework

User Applications

System Call Interface File Operation System Calls File System Operation calls Other System calls

read () write ()

  • pen ()

c l

  • s

e ( ) mkdir () rmdir () link () ioctl () creat () lseek () mount () umount () Statfs() sync () Vnode interfaces VFS interfaces UFS (2) NFS (2) VxFS HSFS QFS UFS(1) NFS (1) PCFS

PCFS

Network Optical drive

Data Data Data Data

MFS

Vnode VFS interface

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  • Transparent to users and applications
  • No re-compilation or re-link needed
  • Transparent to existing file structures
  • Same pathname access
  • Transparent to underlying file systems
  • UFS, NFS

Transparency

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  • Conventional Mount
  • One directory, one file system
  • MFS Mount
  • One directory, two or more file systems

Mount Mechanism

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# mount –F mfs host:/ndir1/ndir2 /udir1/udir2

  • First mount the NFS on a UFS directory
  • Then mount the MFS on top of UFS and NFS
  • Existing UFS tree structure /udir1/udir2

becomes a local copy of MFS

  • Newly mounted host:/ndir1/ndir2 becomes a

remote copy of MFS

  • Same mount options as NFS except no ‘-o hard’
  • ption

Mount Mechanism

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# /usr/lib/fs/mfs/mfsck mfs_dir

  • After MFS mount succeeds, the local copy may

not be identical to the remote copy.

  • Use mfsck (the MFS fsck) to synchronize them.
  • The mfs_dir can be any directory under MFS

mount point.

  • Multiple mfsck commands can be invoked at the

same time.

MFS mfsck Command

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READ/WRITE Vnode Operation

  • All VFS/vnode operations received by MFS
  • READ related operation: read, getattr,….

those operations only need to go to local copy (UFS).

  • WRITE related operation: write, setattr,…..

those operations go to both local (UFS) and remote (NFS) copy simultaneously (using threads)

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  • Directory Level
  • Mirror any UFS directory instead of entire UFS

file system

  • Directory A mirrored to Server A
  • Directory B mirrored to Server B
  • Block Level Update
  • Only changed block is mirrored

Mirroring Granularity

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# /usr/lib/fs/mfs/msync mfs_root_dir

  • A daemon that synchronizes MFS pair after a

remote MFS partner fails.

  • Upon a write failure, MFS:
  • Logs name of file to which the write operation failed
  • Starts a heartbeat thread to verify the remote MFS

server is back online

  • Once the remote MFS server is back online, msync

uses the log to sync missing files to remote server.

MFS msync Command

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Active/Active Configuration

Server Server

Application Application Data A UFS Application Application Data B UFS

Active MFS Server MFS MFS Active MFS Server

NFS NFS

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MFS uses UFS, NFS file record lock. Locking is required for the active-active configuration. Locking enables write-related vnode operations as atomic operations. Locking is enabled by default. Locking is not necessary in active-passive configuration.

MFS Locking Mechanism

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  • Real-time
  • - Replicate file in real-time
  • Scheduled
  • - Log file path, offset and size
  • - Replicate only changed portion of a file

Real -Time and Scheduled

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  • Online File Backup
  • Server File Backup, active  passive
  • Server/NAS Clustering, active  Active

Applications

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Application Application Data NTFS Application Application Data NTFS

Remote Server

MFS = NTFS + CIFS

Window Desktop/Laptop MFS

CIFS

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MFS

User Desktop/Laptop

Online File Backup

Real-time or Scheduled time

Folder

ISP Server

MFS

Folder

MFS

Folder

LAN or Wan LAN or Wan

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Secondary

Server Replication

Mirror File System Mirror File System App Primary Email Mirror File System Mirroring Path : /home : /var/spool/mail Heartbeat

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Enterprise Clusters

Mirror File System Mirror File System

Mirroring Path

App App App App App Mirror File System Mirror File System Central Mirror File System App App