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SIAD.T.7. DC_Storage_LVMS
- 1. SIAD 2023/2024 ©PS/TC DEI/FCTUC SIAD Serviços e Infraestruturas de Alto Desempenho LVMS and ZFS
- 2. SIAD 2023/2024 ©PS/TC DEI/FCTUC 2 Last week: • RAID systems revisited • Intelligent data storage systems • DAS systems • SAN systems • Fibre Channel • iSCSI • FCoE • FCIP • NAS systems • NFS
- 3. SIAD 2023/2024 ©PS/TC DEI/FCTUC 3 This week: • LVMS – Logical Volume Management Systems • The concept of file system snapshot • Block-based access vs. object-based access • ZFS as a modern file system & its implications on the data center
- 4. SIAD 2023/2024 ©PS/TC DEI/FCTUC 4 Logical Volume Manager Concepts A virtual file system is built up from • PV: Physical Volumes (partitions on disks that form a volume group) • VG: Volume Groups (virtual disks) • LV: Logical Volumes (logical volume or mountable partition) • PE: Physical Extent (mini partitions who build up LV) Virtual file systems are flexible • increase/decrease ”disk-space” while running • easily manage fast growing virtual disks • use dynamic growing virtual disks LV’s work like standard disk devices • can be raided Not dependent on single disks for storage Take snapshots of LV’s as backup mechanism
- 5. SIAD 2023/2024 ©PS/TC DEI/FCTUC 5 Logical Volume Manager Concept • One or several disks have one or more partitions • VG is built up from several partitions on several disks • LV is a part of or a whole VG • The LV may be mounted as any other disk device MP: Mounting point
- 6. SIAD 2023/2024 ©PS/TC DEI/FCTUC 6 Snapshots Virtual read-only copy of filesystem • Snapshot has same contents that filesystem had when snapshot was made. • Snapshot uses pointers to data and copy-on-write (COW) to avoid making a copy of entire filesystem. • Snapshots may require as few as ~1% of the size of the filesystem
- 7. SIAD 2023/2024 ©PS/TC DEI/FCTUC 7 Applications of snapshots Faster restore operations: • snapshots take seconds to create or restore from. • The lifetime of snapshots for this purpose may be as short as 1 minute or as long as a few days. • These snapshots won’t help you if disk or other hardware fails. They are NOT backups!!! Staging for backups: • Snapshot filesystem before starting backup. • Files on snapshot do not change during backup (simpler to keep consistent backups). • Snapshot lifetime is how long it takes to backup
- 8. SIAD 2023/2024 ©PS/TC DEI/FCTUC 8 Linux LVM snapshots Linux LVM can create snapshots of logical volumes Example: lvcreate -L500M -s -n backup /dev/db/db1 • creates snapshot (-s) volume named backup • volume is snapshot of /dev/db/db1 LV • can make 500M of changes. What happens if volume of changes exceeds 500M? • LV can’t receive copies of old data if changes are made to original logical volume. • Ensure 500M is more than enough space for changes made during lifetime of snapshot LV snapshots vs. VM snapshots • Similar but different concepts • Snapshot of file systems alone does not guarantee VM snapshot
- 9. SIAD 2023/2024 ©PS/TC DEI/FCTUC 9 Examples of LVMS: LINUX LVM • http://www.globalknowledge.com/training/videodetail.asp?pageid=2222&vid=33 • http://www.howtoforge.com/linux_lvm Solaris Volume Manager Veritas Volume Manager IBM LVM NetBSD LVM Windows Logical Disk Manager … Full list: http://en.wikipedia.org/wiki/Logical_volume_management
- 10. SIAD 2023/2024 ©PS/TC DEI/FCTUC 10 Ephemeral, block and object storage Source: OpenStack Operations Guide
- 11. SIAD 2023/2024 ©PS/TC DEI/FCTUC 11 ZFS as a modern filesystem (and LVM system) Despite the usage of LVMS, most filesystems were not designed for current data centers. ZFS and Btrfs are modern file systems with a few technologies specifically designed for modern data centers. • Joksimoski and Loskovska, Overview of Modern File Systems http://ciit.finki.ukim.mk/data/papers/7CiiT/7CiiT-09.pdf For a very good introduction to ZFS (despite all the hype): • http://www.slideshare.net/mewandalmeida/zfs (these slides will be directly used in the rest of today’s class) • https://www.youtube.com/watch?v=0oJ0vlzeJio (long video, but also quite good)