Ploop/diskinodes - Revision history

Kir: removed translate tags

2021-03-10T15:03:21Z

removed translate tags

Kir at 14:57, 10 March 2021

2021-03-10T14:57:55Z

Sergey Bronnikov: Marked this version for translation

2015-12-26T08:42:30Z

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2015-12-25T22:41:14Z

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Kir: use template:note to highlight the version of vzctl in which set --diskinodes is working for ploop

2015-04-10T21:15:12Z

use template:note to highlight the version of vzctl in which set --diskinodes is working for ploop

Kir: /* Limitations */

2014-11-24T21:22:00Z

‎Limitations

Kir: tagline added ;)

2014-11-11T03:47:31Z

tagline added ;)

Kir: categorized

2014-11-11T03:37:12Z

categorized

Kir: created

2014-11-11T03:36:39Z

created

New page

== Limitations ==

With simfs layout, vzquota is used to set limits for DISKSPACE and
DISKINODES, so these limits can be changed any time.

Unlike simfs, ploop contains a real file system, so amount of disk space
and disk inodes are properties of the file system, determined while
creating a filesystem. It is possible to resize an ext4 file system
in terms of disk space, but there's no way to change the number of available
inodes.

{{Note|There is no way to change DISKINODES for existing ploop. This is a limitation of ext4.}}

In other words, <code>vzctl set --diskinodes</code> is ignored for ploop layout.

== Default value ==

By default, ext4 allocates 1 (one) inode per each 16 KB of data; this is
practically the same as to assume that the average file size will be 16KB.

For example, when creating a ploop with 40GB of disk space, 2621440 inodes
will be available:

<math>\frac{40 * 1024 * 1024}{16} = 2621440</math>

== Increasing ==

If the above default is too low for your usage (for example, a container
has or will have too many small files), you can specify a larger value
for DISKINODES '''during container creation or conversion only'''.
The feature works since vzctl 4.7.

{{Note|You can only specify <code>--diskinodes</code> for <code>vzctl create</code> or <code>vzctl convert</code>.}}

The way it works is the following. First, a file system big enough
to accommodate the requested number of DISKINODES is created, and then
ploop resize is performed to downsize the file system to meet the
requested amount of DISKSPACE.

Example:

vzctl create 123 --diskspace 40G --diskinodes 5242880

Here, a filesystem big enough to have 5242880 of diskinodes
will be created (it's 5242880 * 16K = 80G), then downsized to 40G.

== Issues ==

=== Too high DISKINODES value ===

Sometimes, when the amount of DISKINODES specified is too high,
a very large filesystem is created, and it can not be downsized
to a specified amount. In this case, the following error will be
shown when converting a container from simfs to ploop:

vzctl set ''CTID'' --diskspace 40G --diskinodes 1000000000 --save
...
vzctl convert ''CTID''
...
Error in ploop_resize_image (ploop.c:2477): Unable to change image size to 83877888 sectors, minimal size is 502423144
Unmounting file system at /vz/private/101.ploop/root.hdd/root.hdd.mnt
Unmounting device /dev/ploop37776
Failed to resize image: Error in ploop_resize_image (ploop.c:2477): Unable to change image size to 83877888 sectors, minimal size is 502423144 [38]

In this case, 1G inodes requirement leads to creation of 16TB filesystem
(remember, 1 inode per 16K). Unfortunately, such huge FS can't be downsized
to as low as 40G, the minimum seems to be around 240G (values printed in
the error message are in sectors which are 512 bytes each).

'''Solution 1''': please be reasonable when requesting diskinodes for ploop.

'''Solution 2''': please set DISKINODES to 0 before conversion:

vzctl stop ''CTID''
vzctl set ''CTID'' --diskspace ''xxx''G--diskinodes 0 --save
vzctl convert ''CTID''

This will lead to creating a filesystem with default number of inodes.

=== Too low DISKINODES value ===

If DISKINODES specified during <code>create</code> or <code>convert</code> is
lower than the default (1 inode per 16K of disk space), it is silently ignored.
In other words, there is no way to limit DISKINODES to lower than DISKSPACE / 16384.

== See also ==
* {{git commit|vzctl|ef320d32a4}}
* https://lists.openvz.org/pipermail/users/2014-October/005913.html

@@ Line 1: / Line 1: @@
 Everything you wanted to know about DISKINODES for ploop but were afraid to ask.
@@ Line 90: / Line 91: @@
 * {{git commit|vzctl|ef320d32a4}}
 * https://lists.openvz.org/pipermail/users/2014-October/005913.html
 [[Category: Storage]]

← Older revision		Revision as of 03:47, 11 November 2014
Line 1:		Line 1:
		+	Everything you wanted to know about DISKINODES for ploop but were afraid to ask.
		+
	== Limitations ==		== Limitations ==

← Older revision		Revision as of 03:37, 11 November 2014
Line 87:		Line 87:
	* {{git commit\|vzctl\|ef320d32a4}}		* {{git commit\|vzctl\|ef320d32a4}}
	* https://lists.openvz.org/pipermail/users/2014-October/005913.html		* https://lists.openvz.org/pipermail/users/2014-October/005913.html
		+
		+	[[Category: Storage]]

@@ Line 1: / Line 1: @@
 Everything you wanted to know about DISKINODES for ploop but were afraid to ask.
-== Limitations == <!--T:2-->
+== Limitations ==
 With simfs layout, vzquota is used to set limits for DISKSPACE and
 DISKINODES, so these limits can be changed any time.
 Unlike simfs, ploop contains a real file system, so amount of disk space
 and disk inodes are properties of the file system, determined while
@@ Line 16: / Line 12: @@
 inodes.
 {{Note|There is no way to change DISKINODES for existing ploop. This is a limitation of ext4.}}
 In other words, <code>vzctl set --diskinodes</code> is ignored for ploop layout -- it can only be specified on create.
-== Default value == <!--T:7-->
+== Default value ==
 By default, ext4 allocates 1 (one) inode per each 16 KB of data; this is
 practically the same as to assume that the average file size will be 16KB.
 For example, when creating a ploop with 40GB of disk space, 2621440 inodes
 will be available:
 <math>\frac{40 * 1024 * 1024}{16} = 2621440</math>
-== Increasing == <!--T:11-->
+== Increasing ==
 If the above default is too low for your usage (for example, a container
 has or will have too many small files), you can specify a larger value
 for DISKINODES '''during container creation or conversion only'''.
 {{Note|The feature works since vzctl 4.7.}}
 {{Note|You can only specify <code>--diskinodes</code> for <code>vzctl create</code> or <code>vzctl convert</code>.}}
 The way it works is the following. First, a file system big enough
 to accommodate the requested number of DISKINODES is created, and then
@@ Line 54: / Line 41: @@
 requested amount of DISKSPACE.
 Example:
-  <!--T:17-->
+  vzctl create 123 --diskspace 40G --diskinodes 5242880
 vzctl create 123 --diskspace 40G --diskinodes 5242880
 Here, a filesystem big enough to have 5242880 of diskinodes
 will be created (it's 5242880 * 16K = 80G), then downsized to 40G.
-== Issues == <!--T:19-->
+== Issues ==
-=== Too high DISKINODES value === <!--T:20-->
+=== Too high DISKINODES value ===
 Sometimes, when the amount of DISKINODES specified is too high,
 a very large filesystem is created, and it can not be downsized
@@ Line 74: / Line 58: @@
 shown when converting a container from simfs to ploop:
-  <!--T:22-->
+  vzctl set ''CTID'' --diskspace  40G --diskinodes 1000000000 --save
   ...
   vzctl convert ''CTID''
@@ Line 84: / Line 67: @@
   Failed to resize image: Error in ploop_resize_image (ploop.c:2477): Unable to change image size to 83877888 sectors, minimal size is 502423144 [38]
 In this case, 1G inodes requirement leads to creation of 16TB filesystem
 (remember, 1 inode per 16K). Unfortunately, such huge FS can't be downsized
@@ Line 90: / Line 72: @@
 the error message are in sectors which are 512 bytes each).
 '''Solution 1''': please be reasonable when requesting diskinodes for ploop.
 '''Solution 2''': please set DISKINODES to 0 before conversion:
-  <!--T:26-->
+  vzctl stop ''CTID''
   vzctl set ''CTID'' --diskspace ''xxx''G --diskinodes 0 --save
   vzctl convert ''CTID''
 This will lead to creating a filesystem with default number of inodes.
-=== Too low DISKINODES value === <!--T:28-->
+=== Too low DISKINODES value ===
 If DISKINODES specified during <code>create</code> or <code>convert</code> is
 lower than the default (1 inode per 16K of disk space), it is silently ignored.
 In other words, there is no way to limit DISKINODES to lower than DISKSPACE / 16384.
-== See also == <!--T:30-->
+== See also ==
 * {{git commit|vzctl|ef320d32a4}}
 * https://lists.openvz.org/pipermail/users/2014-October/005913.html
 [[Category: Storage]]