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Old 03-13-2013, 05:29 PM   #16
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@Philip Lacroix => The GeodSoft link is excellect, very comprehensive indeed thank you very much -

Old 03-13-2013, 11:29 PM   #17
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LVM vs 'normal':
Normal partitions are the basic way of separating areas of the system into separate parts, thus giving them their own space. See the cmds
df -hT

# switch is lowercase L
fdisk -l
However, if a partition fills up, it is awkward to extend or re-arrange them

With LVM, you create a disk as an LVM type (type 8e in fdisk) which is called a PV = physical volume. You then group these into a Volume Group (VG), effectively a pool of disk space.
You can then split the VG into LVs (logical volumes), which actually have a filesystem eg ext4 on them.
With this arrangement, you can add more PVs to extend the VG to extend a given LV.
You can also (carefully) remove the PVs and eg re-assign to another VG.

However, unless you have (or will have) a large amt of disks, this is (usually) an unnecessary complication eg for a home system eg if you've only got one or two disks.
NB: its a personal choice at the end of the day.

Note also that that is all LV/VG/PVs are; they do not provide redundancy; for that you need RAID.
FYI: RAID is NOT a substitute for backups!

If you really want to play around, you can create a RAID, then put LVM on top, but is fiddly and coud be tricky to fix if one of the disks does die.

You should read up on RAID and LVM, but you're not likely to need them unless you are at work or have a personal server.

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Old 03-14-2013, 05:32 AM   #18
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Standard Partitions:
  1. Standard partitions are located physically on the disk. The partitions are direct device names and its partition table is located in MBR.
  2. Partitions define a size and type, more specifically, they define a start and end cylinder which essentially defines the size. Obviously, if you've got four partitions, changing the second partition end cylinder affects the third and fourth partitions start cylinders and so you get into a messy situation.
  3. Because they are so closely tied to the disk, setting up a "correct" partitioning scheme upon install is important. If suddenly, a machine function changes or if you're a novice and you've not understood the implications of partitioning, or if you're underestimated disk usage somehow, then changing that partitioning can be cumbersome. There are tools for doing it, but you generally need to move data off the partition to change it
LVM: LVM provide the following advantages over using standard physical storage directly:
  1. When using logical volumes, file systems can extend across multiple disks, since you can join disks and partitions into a single logical volume.
  2. You can extend logical volumes or reduce logical volumes in size with simple software commands, without reformatting and repartitioning the underlying disk devices.
  3. Online data relocation: You can move data while your system is active. Data can be rearranged on disks while the disks are in use. For example, you can empty a hot-swappable disk before removing it.
  4. Convenient device naming: The logical volume manager also allows management of storage volumes in user-defined groups, allowing the user to deal with sensibly named volume groups such as "development" and "sales" rather than physical disk names such as "sda" and "sdb".
  5. Disk striping: You can create a logical volume that stripes data across two or more disks. This can dramatically increase throughput/speed.
  6. Mirroring volumes: Logical volumes provide a convenient way to configure a mirror for your data.
  7. Volume Snapshots: Using logical volumes, you can take device snapshots for consistent backups or to test the effect of changes without affecting the real data.

Note: Starting from rhel/centos 6.4, logical volumes can now be thinly provisioned. This allows you to create logical volumes that are larger than the available disk space. The thin pool can be expanded dynamically when needed for cost-effective allocation of storage space.

Source: Logical Volume Manager Administration

Last edited by mddnix; 03-14-2013 at 05:45 AM. Reason: update
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Old 05-15-2013, 04:05 PM   #19
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@Chrism apologies I just saw this post today - I was unaware there where more posts - that post Chrism was indispensable thank you very much for that..

Old 05-15-2013, 04:14 PM   #20
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@Mddesai apologies as I just saw this posting on partitions today - thank you for adding more clarity to Chrism01s post, your information allows me to put two and two as your response on this thread complimented Chrim01s post perfectly - thank you guys



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