Linux, Unix, NAS, File Systems: Inodes (Part 1) – Checking Availability And High Level Overview
Inodes really tell you how many file handles (files) that can be created on a file system. Most people will never exceed the default setting when the file system is created, nor even know that one is set. I will eventually go into more detail concerning this topic here on the blog. The majority (not all) of file systems that are used on Linux and Unix do not support dynamic inode allocation. What this means is that if you exceed the inode limit of a file system before the storage space, the remainder will be un-usable. That is until some of the current files are removed.
So here is the really bad part. The inodes on ext2 and ext3 (Linux default type) are statically set when the file system is formatted. You can not go back and change the max inode settings. The exceptions to this that I know of are as follows:
- Reiser4
- VxFS
- XFS
- JFS
- WAFL (NetApp proprietary)
- XZFS
If you are running one of the above and have max inodes issue, you can correct it.
I have been working with computers for over 15 years and have only ran into this problem once. Luckily, it occurred on a NetApp NAS device that had the ability to increase this value on the live file system. The main killer here are tons of small files. In this case, the file system for that NFS share was 40 gigabytes in size and default was ~1 million inode limit. The quick fix for the issue was to increase this to 3 million.
As far as a ext2 and 3 go, the following shows how to query a file system for relevant inode information
root@testbox:~# tune2fs -l /dev/sda1 tune2fs 1.41.3 (12-Oct-2008) Filesystem volume name: <none> Last mounted on: <not available> Filesystem UUID: 56161dd8-9d1d-4c54-851d-938bb88ce6d4 Filesystem magic number: 0xEF53 Filesystem revision #: 1 (dynamic) Filesystem features: has_journal ext_attr resize_inode dir_index filetype needs_recovery sparse_super large_file Filesystem flags: signed_directory_hash Default mount options: (none) Filesystem state: clean Errors behavior: Continue Filesystem OS type: Linux Inode count: 4685824 Block count: 18731782 Reserved block count: 936589 Free blocks: 15534374 Free inodes: 4459463 First block: 0 Block size: 4096 Fragment size: 4096 Reserved GDT blocks: 1019 Blocks per group: 32768 Fragments per group: 32768 Inodes per group: 8192 Inode blocks per group: 256 Filesystem created: Mon Sep 29 16:25:20 2008 Last mount time: Fri Jan 23 14:27:02 2009 Last write time: Fri Jan 23 14:27:02 2009 Mount count: 4 Maximum mount count: 33 Last checked: Thu Jan 15 09:00:37 2009 Check interval: 15552000 (6 months) Next check after: Tue Jul 14 10:00:37 2009 Reserved blocks uid: 0 (user root) Reserved blocks gid: 0 (group root) First inode: 11 Inode size: 128 Journal inode: 8 First orphan inode: 2908742 Default directory hash: tea Directory Hash Seed: a6544c5xxxxxxxxxxxxxxxxx Journal backup: inode blocks
The above is good to know, especially to check an un-mounted file system. The command below shows a friendlier formatted output
root@testbox:~# df -i Filesystem Inodes IUsed IFree IUse% Mounted on /dev/sda1 4685824 226361 4459463 5% / tmpfs 222201 4 222197 1% /lib/init/rw varrun 222201 64 222137 1% /var/run varlock 222201 5 222196 1% /var/lock udev 222201 5142 217059 3% /dev tmpfs 222201 5 222196 1% /dev/shm /dev/sdb1 61063168 1116 61062052 1% /media/disk
As you can see, there are no issues to be worried about on this test computer. Most systems administrators perform centralized monitoring of disk usage at a disk space level (capacity). On highly used servers that utilize locally stored and/or direct attached storage, it is a good idea to have a script check and report on the available inodes.
Notes: This information is provided for a high level overview concerning inodes. More in-depth information will be provided in up-coming posts.
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