6,534
edits
Changes
created
== 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
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