/scratch in CentOS 7
Just as we did in RHEL6, the unused space of the hard drive of a host will be available for anyone to use at /scratch. Nothing has changed in this regard. However, in light of some recent events, we would like to take this opportunity to talk about /scratch and it's purpose.
The first and perhaps most important thing is: /scratch is NOT backed up in any way. Any data that you put on /scratch is solely your own responsibility. If you put critically important files on it, and your machine experiences a hard drive failure, your data could be lost and there may be nothing we can do about it.
/scratch is intended to be what the name intends: a scratch pad, a place to put things which you may need, but which could be lost without much harm. For example, if you have a program that generates a bunch of temporary information in generating an ultimate solution, /scratch is the ideal place. Typically the /scratch partition has a LOT more space available than the root filesystem.
For temporary files, please do not use /tmp. /tmp is a directory for temporary files, but not temporary files explicitly generated by users. Note that /tmp is part of the root filesystem, which contains enough space to hold the operating system and default programs:
user123@box999[modulefiles]$ df -h /tmpFilesystem Size Used Avail Use% Mounted on/dev/mapper/vg_box999-lv_root 50G 20G 31G 39% /user123@box999[modulefiles]$ df -h /scratchFilesystem Size Used Avail Use% Mounted on/dev/mapper/vg_box999-lv_scratch 179G 64M 179G 1% /scratch
Although the hard drive capacity of our various models varies, the above is representative of a typical scenario. There have been case where users have piled up their data into /tmp and filled out the entire root filesystem, which can cause erratic system behavior.
But I have a huge amount of very important data...
If you find that you have a huge amount of data which you can't afford to lose, but which also won't fit into your home directory, apply for a /data directory. A /data directory is similar to the /home directory in that it is NFS mounted and backed up, except that it is intended to house raw data that you cannot afford to lose.
Apply for a /data directory here: Data Directory Request Form