COMP 3430 – Operating Systems
Franklin 23rd, 2022
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By the end of today’s lecture, you should be able to:
▶ Choose an appropriate RAID-level given requirements.
The Rocket Book (Public Domain)
Controllers
Let’s look at a RAID controller.
Note: This is an ancient RAID controller.
Public Domain
What kind of RAID do I want?
Let’s look at some scenarios and decide what RAID level would be appropriate for the problem, situation, or person.
Pixabay License
Scenario 1: the data hoarder
Scenario 2: the gamer
Scenario 3: the scientist
▶ Different file systems are different.
▶ Different RAID-levels serve different needs.
Software RAID
▶ Hardware RAID cards are…
▶ … expensive
▶ … hard to configure
▶ … require your hardware to know about it ▶ Idea: So let’s implement RAID, but in
Soft controllers. ©Forteblast CC BY-SA 3.0
Typical limits for Linux LVM v1: Range of PE size (p): 8KB… 512MB Range of PV size (v): 512MB… 2TB
Range of PEs (N): 1… 65534 Range of PVs (X): 1… 256 Range of VGs(Z): 1… 99
Volume Group1 … Volume GroupZ Physical VolumeX
Physical Volume
Physical Volume1
PE1 PE2 PEN-1 PEN
Logical Volume1
PE2 PEN-1 PEN
Logical VolumeY
Logical Volume2
©Blacknova CC BY-SA 3.0
▶ Let’s take a look at the Linux Kernel’s implementation of LVM
▶ We’ll try to come up with a basic idea of the structure and responsibilities the kernel has when mapping logical I/O to physical I/O.
▶ Let’s start by looking at dm.h and dm.c
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