Linux RHEL file systems

DanGiles

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PREDATAR Control23

After setting up the file systems for TSM on RHEL, I was surpised to see missing space. e.g.

Filesystem Size Used Avail Use% Mounted on
/dev/mapper/tsmvg_db001-tsmlv_db001 126G 188M 120G 1% /tsmdata/db001
...
/dev/mapper/tsmvg_actlog-tsmlv_actlog 126G 188M 120G 1% /tsmdata/actlog
/dev/mapper/tsmvg_archlog-tsmlv_archlog 493G 198M 467G 1% /tsmdata/archlog
/dev/mapper/tsmvg_stg001-tsmlv_stg001 13T 150M 12T 1% /tsmdata/stg001

As you can see, Size-Used<>Avail. I was then given this bit of information:

•In order to protect the filesystem from completely running out of space, which could possibly lead to a system hang, by default sets an option called reserved-blocks-percentage to 5%. This option sets aside a certain percentage of filesystem blocks as reserved. This allows system daemons, such as syslogd, to continue to function correctly in the event a filesystem becomes full. It does this by preventing any non-privileged processes from accessing these reserved blocks.
• Additionally, these reserved blocks are also used by the filesystem to improve performance by reducing file fragmentation.
• Reducing this value from the default is not recommended unless the filesystem is large.

The question becomes, given the way TSM uses these volumes, can I eliminate this reserved space altogether? I intend to use pre-defined volumes for the most part for storage pools.
 
PREDATAR Control23

So, I got a reply back from IBM (that was quick!) and they pointed me to the following APAR:

http://www-01.ibm.com/support/docview.wss?uid=swg1IC85800

Well, it says you can change it, but doesn’t say if you should, and by how much. However, this did give me the proper search pattern to put into google and so I was able to get these:

http://unix.stackexchange.com/questions/7950/reserved-space-for-root-on-a-filesystem-why
http://www.microhowto.info/howto/re..._root_on_an_ext2_ext3_or_ext4_filesystem.html

Which tells me I can get rid of all reserved space :D
 
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