16TB filesystem & inodes

The number of inodes is defined by the nbpi option (during the creation of the fs)

     nbpi=
     The number of bytes per inode block. The default is 8192 bytes.

It can not increased afterwards. I do not think increasing it (when creating the fs) would make much sense.

The inodes of the rootfs do not depend from the inodes or the number of files of a data FS. So stay with the default inodes of the rootfs, it can be extended if necessary later on.

Hi Raymond,

please dont change the rootfs unless directed so by EMC support.

For regular file systems you can get up to 4 billion inodes for a 16TB fs if you set the param mentioned in this post https://community.emc.com/message/432439#432439 *before* you create it or before you extend beyond 2TB.

If the param ufs.inodelimit is at the defalt we will only create up to 256 million inodes (to save space) when creating or expanding a file system.

For an already created 16TB f

Note that the only cases you should need less then 8k npbi is when you have lots of empty files or maybe symlinks.

Otherwise each file takes up at least 8kB disk space

So in order to really need the 4billion inodes in a 16 TB file system all of the files would have to be less than 8kB in length

any files larger than that would would help "free up" some inodes - i.e. a 8 GB file only needs one inode but the 8k nbpi calc creates 1000 inodes for 8GB of disk space.

regards

Rainer

So in order to really need the 4billion inodes in a 16 TB file system all of the files would have to be less than 8kB in length any files larger than that would would help "free up" some inodes - i.e. a 8 GB file only needs one inode but the 8k nbpi calc creates 1000 inodes for 8GB of disk space.

Rainer, can you please explains this again ? Inodes contains information about files, what did you mean when you said

a 8 GB file only needs one inode but the 8k nbpi calc creates 1000 inodes for 8GB of disk space.

Thanks

maybe that was misleading - what I was trying to say is that 8k npbi create an inode per 8k file system size

so if all your files are 8k or less then you roughly get number of inodes you need

now if one of these files is 8GB then you still get 1 million inodes (pro-rated for that space) but only need 1 for that file - so you have 1M-1"left" unused

If you think that through you come to the conclusion that with just a few larger file you will always have more inodes than you need - except you create files/symlinks that dont need data blocks at all

Rainer