Slide 1

Storage Systems: Advanced Topics Learning Objectives: To understand limitations of one file system per partition model To understand Logical Volume Management its motivations and its facilities To understand how Storage Area Networks extend these features to multiple systems To relate LVM and SAN to a most modern file system implementation COMP25212 1

Slide 2

Storage Virtualization File System Code assumes 1 file system to 1 disk drive (partition) Stripe/Mirror/RAID changes this Storage Virtualization: break filesystem/drive relationship COMP25212 2 OS Device Drivers File System

Slide 3

Logical Volume Management Virtual mapping between file system code and physical device Analogous (but not identical!) to virtual memory addressing Volume Group of all drives in a pool Storage space in Volume Group divided into Physical Extents usually all same size Logical Volume is set of Physical Extents COMP25212 3

Slide 4

Logical Volume Management Mirror/Stripe/RAID provided within LVM layer Resize filesystem Snapshot a live filesystem COMP25212 4 OS Device Drivers File System LVM layer Volume Group

Slide 5

e.g. Linux Server / - mostly read want fast seeks swap read/write want high bandwidth /opt infrequent access /var huge, infrequent access Mirror / Stripe swap spare space to /opt and /var COMP25212 5

Slide 6

LVM Example: Now we can share resources more flexibly and more efficiently but only on one server COMP25212 6 Mirror / Stripe swap /var /opt

Slide 7

Storage Area Networking Implement LVM features in separate storage controller Connect multiple servers to storage controller via SCSI, or FibreChannel, or Infiniband, or (n.b. SAN over Ethernet is conventionally called Networked Attached Storage (NAS) Now can share disk resources across multiple servers Rapid migration of disk images COMP25212 7

Slide 8

Storage Area Network Controller COMP25212 8 8 Blade Servers SAN Controller

Slide 9

SAN Key Features Functionality Key element of system virtualization Migrating virtual machines De-duping share common subsets of file systems (think Virtual Machine images!) Management: Manage storage separately from server physical resources Maximize flexibility of storage provisioning COMP25212 9

Slide 10

ZFS Volume Aware File System Marketing claims: Lost a file? Run out of space? Difficult disk upgrade? Want to grow/shrink? Data Corruption? COMP25212 10 Pools of storage

Slide 11

ZFS techniques Lost a file? Copy-on-write simple rollback/recovery Run out of space/Difficult disk upgrade? Add new storage to live systems Self-checking, self-healing Want to grow/shrink? Data Corruption? end-to-end sumchecking COMP25212 11

Slide 12

ZFS Implementation ZFS Combines File Service and Logical Volume Management Is this a good idea? Discuss COMP25212 12