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

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

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

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

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

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

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

8. Storage Area Network Controller COMP25212 8 8 “Blade Servers” SAN Controller

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

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

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

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