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 COMP

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 COMP OS Device Drivers File System

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” COMP

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

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 COMP

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

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 COMP

Storage Area Network Controller COMP “Blade Servers” SAN Controller

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 COMP

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

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 COMP

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