LVM Fun - Revision history

175.140.118.158: /* Volume group creation */

2013-05-14T05:10:53Z

‎Volume group creation

Palica: /* LVM and Funtoo */

2012-11-18T08:57:22Z

‎LVM and Funtoo

68.58.202.138: /* Shrinking a storage space */

2012-07-21T18:09:00Z

‎Shrinking a storage space

68.58.202.138: /* Physical volumes creation */

2012-07-21T17:25:05Z

‎Physical volumes creation

68.58.202.138: /* Concepts */

2012-07-21T17:15:54Z

‎Concepts

77.86.202.46 at 10:28, 27 May 2012

2012-05-27T10:28:31Z

Drobbins at 15:57, 5 January 2012

2012-01-05T15:57:51Z

24.201.209.90: /* More advanced topics */

2011-12-31T14:03:30Z

‎More advanced topics

404 Error: /* More advanced topics */

2011-12-31T04:09:35Z

‎More advanced topics

404 Error: /* Replacing a PV (storage device) by another */

2011-12-31T04:03:36Z

‎Replacing a PV (storage device) by another

@@ Line 160: / Line 160: @@
 Exporting a VG and clustered VG are a bit more advanced aspects of LVM and won't be covered here especially the clustered VGs which are used in the case of a shared storage space used in a cluster of machines. Talking about clustered VGs management in particular would require and entire article in itself. '''For now the only detail you have to worry about those dashes in ''Attrs'' is to see a dash at the 4th position of ''Attrs'' instead of a ''p'''''. Seeing ''p'' there would be a bad news: the VG would have missing parts (PV) making it not usable.
-{{fancynote|In the exact same manner you can see a detailed information about physical volumes with '''pvdisplay''', you can see detailed information of a volume group with '''vgdisplay'''. We will demonstrate that latter command in the next paragraphs.}}
+{{fancynote|In the exact same manner you can see a detailed information about physical volumes with '''pvdisplay''', you can see detailed information of a volume group with '''vgdisplay'''. We will demonstrate that latter command in the paragraphs to follow.}}
 Before leaving the volume group aspect, do you remember the '''pvs''' command shown in the previous paragraphs? Try it gain:

← Older revision		Revision as of 08:57, 18 November 2012
Line 1,096:		Line 1,096:
	[[Category:Labs]]		[[Category:Labs]]
	[[Category:Filesystems]]		[[Category:Filesystems]]
		+	[[Category:Articles]]

@@ Line 749: / Line 749: @@
 == Shrinking a storage space ==
-On some occasions it can be useful to reduce the size of a LV or the size of the VG itself. The principle is similar to what ha been demonstrated in the previous section:
+On some occasions it can be useful to reduce the size of a LV or the size of the VG itself. The principle is similar to what has been demonstrated in the previous section:
 # umount the filesystem belong to the LV to be processed (if your filesystem does not support online shrinking)

@@ Line 57: / Line 57: @@
 </pre>
-It is absolutely normal that nothing in particular is printed at the output of each command but we assure you: you have there LVM PVs. You can check them by issuing:
+It is absolutely normal that nothing in particular is printed at the output of each command but we assure you: you have three LVM PVs. You can check them by issuing:
 <pre>
@@ Line 125: / Line 125: @@
 {{fancynote|It is possible to force how LVM handles the alignments on the physical storage. This is useful when dealing with 4K sectors drives that lies on their physical sectors size. Refer to the manual page. }}
 == Volume group creation ==

@@ Line 7: / Line 7: @@
 = Concepts =
-As usual having a good idea of the concepts lying beneath is mandatory. LVM is not very complicated but it is easy to become confused especially because it is multi-layered system, however LVM designers had the good idea of keeping the command names consistent between all LVM command sets making your life easier.
+As usual, having a good idea of the concepts lying beneath is mandatory. LVM is not very complicated, but it is easy to become confused, especially because it is a multi-layered system; however LVM designers had the good idea of keeping the command names consistent between all LVM command sets, making your life easier.
 LVM consists of, mainly, three things:
@@ Line 13: / Line 13: @@
 * '''Physical volumes (or ''PV'')''': nothing more than a physical storage space. A physical volume can by anything like a partition on a local hard disk, a partition located on a remote SAN disk, a USB key or whatever else that could offer a storage space (so yes, technically it could be possible to use an optical storage device accessed in packet writing mode). The storage space on a physical volumes is divided (and managed) in small units called '''Physical Extents''' (or ''PE''). Just to give an analogy if you are a bit familiar with RAID, PE are a bit like RAID stripes.
 * '''Volume Groups (or ''VG'')''': a group of at least one PV. VG are '''named''' entities and will appear in the system via the device mapper as '''/dev/''volume-group-name'''''.
-* '''Logical Volumes (or ''LV'')''': a '''named''' division of a volume group in which a filesystem is created and that can be mounted in the VFS. Just for the record, just as for the PE in PV, a LV is managed as chucks known as Logical Extents (or ''LE''). Most of the time those LE are hidden to the system administrator due to a 1:1 mapping between them and the PE lying be just beneath but a cool fact to know about LEs is that they can be spread over PV just like RAID stripes in a RAID-0 volume. However, researches done on the Web tends to demonstrate system administrators prefer to build RAID volumes with mdadm then use LVM over them for performance reasons.
+* '''Logical Volumes (or ''LV'')''': a '''named''' division of a volume group in which a filesystem is created and that can be mounted in the VFS. Just for the record, just as for the PE in PV, a LV is managed as chucks known as Logical Extents (or ''LE''). Most of the time those LE are hidden to the system administrator due to a 1:1 mapping between them and the PE lying be just beneath but a cool fact to know about LEs is that they can be spread over PV just like RAID stripes in a RAID-0 volume. However, researches done on the Web tends to demonstrate system administrators prefer to build RAID volumes with mdadm than use LVM over them for performance reasons.
 In short words:  LVM logical volumes (LV) are containers that can hold a single filesystem and which are created inside a volume group (VG) itself composed by an aggregation of at least one physical volumes (PV) themselves stored on various media (usb key, harddisk partition and so on). The data is stored in chunks spread over the various PV.

@@ Line 3: / Line 3: @@
 LVM (Logical Volume Management) offers a great flexibility in managing your storage and significantly reduces server downtimes by allowing on-line disk space management: The great idea beneath LVM is to '''make the data and its storage loosely coupled''' through several layers of abstraction. You (the system administrator) have the hand of each of those layers making the entire space management process extremely simple and flexible though  various set of coherent commands.
-Several other well-known binary Linux distributions makes an aggressive use of LVM and several Unices including HP-UX, AIX and Solaris offers since a while a similar functionality modulo the commands to be used. LVM is not mandatory but its usage can bring you additional flexibility and make your everyday life much more simpler.
+Several other well-known binary Linux distributions makes an aggressive use of LVM and several Unixes including HP-UX, AIX and Solaris offers since a while a similar functionality modulo the commands to be used. LVM is not mandatory but its usage can bring you additional flexibility and make your everyday life much more simpler.
 = Concepts =

← Older revision		Revision as of 15:57, 5 January 2012
Line 1,096:		Line 1,096:

	[[Category:Labs]]		[[Category:Labs]]
		+	[[Category:Filesystems]]

@@ Line 1,088: / Line 1,088: @@
 == Freezing a VG ==
-== Using LVM snapshots ==
+== LVM snapshots ==
-== Enabling multiple LVM metadata copies ==
+== Linear/Stripped/Mirrored Logical volumes ==
 = LVM and Funtoo =

@@ Line 1,071: / Line 1,071: @@
 </pre>
-Final state of teh PVs composing ''vgdata'':
+Final state of the PVs composing ''vgdata'':
 <pre>
 # pvs