Manage your disk space... for free :) Julien Wallior Plug Central - - PowerPoint PPT Presentation

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Manage your disk space... for free :) Julien Wallior Plug Central - - PowerPoint PPT Presentation

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Manage your disk space... for free :) Julien Wallior Plug Central 11.1.2006 Agenda Background RAID Some basics Practice Booting on a raid device LVM What is that? How it works Hardware raid... if you really

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Manage your disk space... for free :)

Julien Wallior

Plug Central 11.1.2006

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Managing your disk space Julien Wallior 11.1.2006

Agenda

  • Background
  • RAID
  • Some basics
  • Practice
  • Booting on a raid device
  • LVM
  • What is that?
  • How it works
  • Hardware raid... if you really want it
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Managing your disk space Julien Wallior 11.1.2006

Background

  • Just got out of college

– I don't want a pay for anything – I don't need that much performance – If it breaks... it's my problem

  • Does it mean this presentation is useless?

– Of course not... – I've been using these technologies

for two years without issue

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Managing your disk space Julien Wallior 11.1.2006

RAID: The Basics

  • Redundant Array of Inexpensive Disks
  • Two usage:

– Performance – Redundancy

  • Different RAID level depending on your needs

– Tradeoffs

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Managing your disk space Julien Wallior 11.1.2006

Basic Levels

  • RAID 0 (stripping)
  • Performance ++
  • Redundancy --
  • RAID 1 (mirroring)
  • Performance
  • Read ++
  • Write --
  • Redundancy ++
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Managing your disk space Julien Wallior 11.1.2006

Fancier (or Funkier)

  • RAID 5

– Distributed Parity

  • Performance
  • Read ++
  • Write -
  • Redundancy +
  • Less popular

– Dedicated parity disk

  • RAID 3

– Byte level stripping

  • RAID 4

– Block level stripping

– Two parity disks

  • RAID 6

– Like RAID 5

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Managing your disk space Julien Wallior 11.1.2006

The Combos

  • RAID 0+1
  • RAID 1+0

What's the difference???

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Managing your disk space Julien Wallior 11.1.2006

mdadm...

  • Some nice features:

– integrated in the OS – spare drives – email when a disk fails – periodic rebuild

  • Enough theory for now...
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Managing your disk space Julien Wallior 11.1.2006

Let's play a little bit

  • Create a raid 5 array with one hot spare
  • mdadm --create /dev/md0 --raid-devices=3 --spare-

device=1 --level=5 /dev/ram0 /dev/ram1 /dev/ram2 /dev/ram3

  • Check the state of the array
  • mdadm --detail /dev/md0
  • cat /proc/mdstat
  • Simulate a drive failure
  • mdadm --manage /dev/md0 --set-faulty /dev/ram0
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Managing your disk space Julien Wallior 11.1.2006

Let's play a little bit

  • Hot remove a drive
  • mdadm --manage /dev/md0 --remove /dev/ram0
  • Hot add a drive
  • mdadm --manage /dev/md0 --add /dev/ram4
  • Some performance measurements

– Raid 5 vs Raid 1 write: 7 times slower !

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Managing your disk space Julien Wallior 11.1.2006

Booting on it?

  • It works...
  • Little tricky grub setup (mbr not mirrored)

– grub> device (hd0) /dev/hda – grub> root (hd0,0) – grub> setup (hd0) – grub> device (hd0) /dev/hdb – grub> root (hd0,0) – grub> setup (hd0) – grub> exit

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Managing your disk space Julien Wallior 11.1.2006

LVM: what is that?

  • Logical Volume Manager
  • LVM2 is standard in kernel 2.6
  • Physical volume (pv...)
  • Volume group (vg...)
  • Logical volume (lv...)
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Managing your disk space Julien Wallior 11.1.2006

Why would I use it?

  • Partition spread across multiple disks

– different than RAID0 (no stripping)

  • Resize partition of the fly

– you just need to unmount it – don't forget to resize the filesystem (resize2fs)

  • Snapshots

– very useful for backups – requires free space in the volume group

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Managing your disk space Julien Wallior 11.1.2006

Let's see something

  • Enough talking...

– Our goal:

  • RAID for redundancy
  • LVM for flexibility
  • Demo...
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Managing your disk space Julien Wallior 11.1.2006

Physical Volume

  • Creation
  • pvcreate /dev/md0
  • Get config
  • pvs
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Managing your disk space Julien Wallior 11.1.2006

Volume group

  • Creation
  • vgcreate vg1 /dev/md0
  • Get config
  • vgs
  • Add a new physical volume
  • vgextend vg1 /dev/ram5
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Managing your disk space Julien Wallior 11.1.2006

Logical volume

  • Creation
  • lvcreate --name lv1 --size 80M vg1
  • mkfs.ext3 /dev/mapper/vg1-lv1
  • mount /dev/mapper/vg1-lv1 /mnt
  • Get state
  • lvs
  • Resize
  • resize2fs /dev/mapper/vg1-lv1 80M (don't forget it)
  • lvresize -L -20M /dev/vg1/lv1
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Managing your disk space Julien Wallior 11.1.2006

Snapshot

  • Takes a snapshot of a logical volume
  • modprobe dm-snapshot
  • Creation
  • lvcreate --snapshot --name lv1-snapshot1 --size 80M

/dev/vg1/lv1

  • Deletion
  • lvremove /dev/vg1/lv1-snapshot1
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Managing your disk space Julien Wallior 11.1.2006

Hardware

  • Better performances... more expensive
  • On HP Proliant servers
  • Utility hpacucli for linux
  • ctrl slot=0 pd all show
  • ctrl slot=0 ld all show
  • ctrl slot=0 create type=ld drives=2:0,2:1 raid=1
  • Hot plug and hot swap the disks...
  • Basically it works and it's no fun at all :)
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Managing your disk space Julien Wallior 11.1.2006

Conclusion

  • Personal experience:

– You can really do a lot – Excellent mean to learn how it works – It's amazing how well it works

  • Sorry for the french accent :)
  • One last thing: make a backup before

messing around with these things.

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Managing your disk space Julien Wallior 11.1.2006

Thank you

Questions ?