Disk quota, df and stat weird behaviour - Revision history

Kir: /* Other reasons of strange numbers */ +ext4

2012-04-06T21:34:39Z

‎Other reasons of strange numbers: +ext4

2008-01-24T08:54:37Z

2008-01-24T08:53:30Z

VE -> container, some rewording and reformatting, categorization

2008-01-24T07:09:26Z

categorized

2006-12-12T10:19:39Z

‎Cases Summarizing Table: bad formule fix in table

2006-12-12T10:16:53Z

small missprint

2006-12-12T10:15:49Z

Fixing a bad missprint in formule, marked by Andrey

2006-12-01T11:10:32Z

images created by Roma are added.

2006-12-01T11:08:52Z

‎'''Quota is on for VE and there is NOT enough space on partition''': Other illustrations are added

2006-12-01T10:56:25Z

‎'''Quota is on for VE and there is enough space on partition''' ( illustration 1 ): gif -> png

@@ Line 154: / Line 154: @@
 At the moment I see only two more reasons why numbers in <code>df</code>/<code>stat</code> output can confuse you.
 # The quota is inconsistent. This can happen if you turned quota off for some time, if you wrote directly to private area (<code>/vz/private</code>), but not through <code>simfs</code>, etc. When you have doubts whether your quota is consistent or not, just drop quota (<code>vzquota drop <ctid></code>, where <code><ctid></code> is the id of a stopped [[CT]]). While starting [[CT]], <code>vzctl</code> will automatically initialize quota.
-# Unsupported underlying filesystem. Currently OpenVZ quota only supports <code>ext2</code> and <code>ext3</code>. With other file system types you can have unpredictable results. Praemonitus praemunitus!
+# Unsupported underlying filesystem. Currently OpenVZ quota only supports <code>ext2</code>, <code>ext3</code> and <code>ext4</code>. With other file system types you can have unpredictable results. Praemonitus praemunitus!
 == TODO ==

← Older revision		Revision as of 07:09, 24 January 2008
Line 143:		Line 143:
	== TODO ==		== TODO ==
	TODO: Add examples with stat/df		TODO: Add examples with stat/df
		+
		+	[[Category: Troubleshooting]]
		+	[[Category: Resource management]]

@@ Line 129: / Line 129: @@
 | <math>free_{ext2} \le quota_{limit} - quota_{used}</math>
 <math>avail_{ext2} \le quota_{limit} - quota_{used}</math>
-| <math>total_{simfs} = total_{ext2} - ( quota_{barrier} - quota_{usage} )</math>
+| <math>total_{simfs} = quota_{usage} + free_{ext2}</math>
 <math>free_{simfs} = free_{ext2}</math>

@@ Line 71: / Line 71: @@
 :: <math>total_{simfs} = quota_{usage} + free_{ext2}</math> (4)
 : Substituting (4) in (3) obtain:
-:: <math>df_{usage} = total_{simfs} - free_simfs = quota_{usage} + free_{ext2} - free_{ext2} = quota_{usage} = const</math>
+:: <math>df_{usage} = total_{simfs} - free_{simfs} = quota_{usage} + free_{ext2} - free_{ext2} = quota_{usage} = const</math>
 :  In this case, administrator of [[VE]] #1 sees that total amount of space decreases, but usage however is constant.
 : The same reasoning as with <math>free_{simfs}</math> suits for calculating <math>avail_simfs</math>. Two cases are possible. If

@@ Line 69: / Line 69: @@
 :: <math>df_{usage} = total_{simfs} - free_{simfs} = total_{simfs} - free_{ext2}</math> (3)
 : <math>free_{ext2}</math> decreases because [[VE]] #2 writes to disc, consequently <math>df_{usage}</math> increases! "What the hell is going on?!" - thinks the administrator - "Nobody writes on the disk in my [[VE]], but the usage increases!" To avoid such situation the following approach is used in OpenVZ: decrease <math>total_{simfs}</math> so, that <math>df_{usage}</math> remains the same, i.e.:
-:: <math>total_{simfs} = total_{ext2} - (quota_{barrier} - quota_{usage})</math> (4)
+:: <math>total_{simfs} = quota_{usage} + free_{ext2}</math> (4)
 : Substituting (4) in (3) obtain:
-:: <math>df_{usage} =  (total_{ext2} - free_{ext2}) - (quota_{barrier} - quota_{usage}) = const</math>
+:: <math>df_{usage} = total_{simfs} - free_simfs = quota_{usage} + free_{ext2} - free_{ext2} = quota_{usage} = const</math>
 :  In this case, administrator of [[VE]] #1 sees that total amount of space decreases, but usage however is constant.
 : The same reasoning as with <math>free_{simfs}</math> suits for calculating <math>avail_simfs</math>. Two cases are possible. If

← Older revision	Revision as of 08:54, 24 January 2008
(No difference)

← Older revision		Revision as of 11:10, 1 December 2006
Line 142:		Line 142:

	== TODO ==		== TODO ==
−
−	~~TODO: Add Roma's images~~
−
	TODO: Add examples with stat/df		TODO: Add examples with stat/df

@@ Line 61: / Line 61: @@
 :: <math>free_{simfs} = quota_{barrier} - quota_{used}</math>
-=== '''Quota is on for VE and there is NOT enough space on partition''' ===
+=== '''Quota is on for VE and there is NOT enough space on partition''' ([[:Image:Vzquota2.png|illustration 2]], [[:Image:Vzquota3.png|illustration 3]], [[:Image:Vzquota4.png|illustration 4]], [[:Image:Vzquota5.png|illustration 5]]) ===
 : This is the most interesting and difficult to explain case. Nevertheless I tried to do it. So, our assumption is that:
 :: <math>quota_{barrier} - quota_{used} > free_{ext2}</math>

@@ Line 47: / Line 47: @@
 : thus in [[VE]] you obtain information about disk usage of partition, but not disk usage of [[VE]].
-=== '''Quota is on for VE and there is enough space on partition''' ( [[:Image:Vzquota1.gif|illustration 1]] ) ===
+=== '''Quota is on for VE and there is enough space on partition''' ( [[:Image:Vzquota1.png|illustration 1]]) ===
 : If quota is on, amount of disk space that [[VE]] potentially can acquire should be equal quota barrier:
 :: <math>total_{simfs} = quota_{barrier}</math>