[Moller] [Jlab-scicomp-briefs] JLab farm cache system upgrades on May 17

[Jie Chen]

Dear JLab Scientific Computing Users:

JLab farm disk cache system will undergo a major change on the upcoming 
maintenance day of May 17. The current read-only cache will be upgraded 
into a new write-through cache system which not only offers all 
capabilities of the current system but also enables a user with 
appropriate permission to deposit new files into the cache. The new 
files will be migrated into the tape library after a short period of 
time within which the files can be modified or deleted. The purpose of 
this upgrade is to increase the efficiency of the disk file system and 
the tape library usage, to offer users an easier way to put files into 
the tape library, and to provide better control of file system hierarchy 
within any physics experimental project.

The upgrade will have a minimal impact to users.  For example, all Auger 
job submission scripts do not need to be changed, and majority of jcache 
sub-commands are still valid. However, there are a few things worth 
noticing:

1. Cache directory on farm nodes is changed from /cache/mss/xyz to 
/cache/xyz. If one has to access a mounted cache directory directly, 
please make sure the new location of the cache directory.

2. The new cache system looks like a file system on top of the tape 
library. However, the permission and ownership settings are controlled 
by the tape library software (JasMine). If a user wants to change group 
or permission of a directory, he/she should not use chgrp or chmod on 
the directory. Instead the user should use jcache chgrp/chmod command to 
accomplish the task. The new command not only changes the 
group/permission of a directory on the disk but also updates the 
appropriate information inside the tape library.

3. A newly created file will be backed up to the tape library if its 
size is larger than 3 MB and the file is older than the backup threshold 
(12 days).

For more information, please consult the write-through cache 
documentation at

https://scicomp.jlab.org/docs/write-through-cache

Send comments and suggestions to scicomp at jlab.org. Thank you very much.

Sincerely,


Your scicomp team.

-- 
################################################################
#     Jie Chen
#     Scientific Computing Group
#     Jefferson Lab
#     12000 Jefferson Ave
#     Newport News, VA 23606
#     757-269-5046
#     chen at jlab.org
################################################################					
					

_______________________________________________
Jlab-scicomp-briefs mailing list
Jlab-scicomp-briefs at jlab.org
https://mailman.jlab.org/mailman/listinfo/jlab-scicomp-briefs