Temp And Logging Space Configuration; Copyright © 2011 Caringo, Inc - Dell DX6000G Setup And Configuration Manual

Appendix A. Temp and Logging Space Configuration
Every file that is written to or read from the DX Storage cluster will be cached in the location
specified for the spooler directory during the installation process. The spooler directory is integral
to the internal function of DX Storage CFS and should never be manually manipulated, particularly
while CFS is actively running. Consequently, it is important that the directory be properly configured
prior to using CFS. The spool directory's file system should be configured with enough space to
keep the default maximum of 100,000 files and should be no smaller than 50GB. It must also be
large enough to hold 2X the largest data file being written. When allocating disk space, be sure to
allow for adequate logging space if you selected to log to a file (max of 8 log files with 512MB each).
In addition to the spool and logging space required for CFS, CNS maintains a lookup file in /var/lib.
The size of this file will grow approximately 1Gb per 10 million files stored in the name space. To
ensure there is adequate space for swapping of this file, 2Gb of free space must be available per 10
million files written to the name space.
If files in your system will be large, verify that the file system type will support sufficiently large files
and extended attributes. The mount option 'user_xattr' must be included in the /etc/fstab entry for
the spooler partition. Ext3 is recommended, although there are plenty of valid choices. A good
feature comparison is available on the Wikipedia at the following URL:
Comparison_of_file_systems
Note
If you are using an Ext3 file system, the 'dir_index' option should be enabled by default
but should be verified for performance, particularly in situations where there are a large
number of files per directory. To determine whether the option is already enabled, run the
following command:
sudo debugfs -R feature /dev/sda1
where '/dev/sda1' represents the disk partition where the temp space resides. If the
returned list contains a 'dir_index' option, no further action is needed. Otherwise you can
enable this option using the following command, again replacing /dev/sda1 with the disk
partition where the temp space resides:
sudo tunefs -O dir_index /dev/sda1
If the available space on the partition where the spool/cache directories reside gets too low or the
file count exceeds 100,000, cached files with the oldest access dates will be flushed until adequate
space has been regained. If more than 65% of the available space for the configured partition
is utilized, the least recently used cached files are flushed until the cache is reduced by 10%.
When 80% of available spool space is consumed, CFS will start returning out of space errors. The
evaluation of available space considers all usage for the partition, not just CFS usage, and includes
any reserved space you have explicitly dedicated for other purposes. For this reason, best practice
is to configure a dedicated partition for the CFS spool/cache with a minimum of 50GB of available
space. Environments writing large files under high throughput conditions may need to tune their
cache eviction percentages to prevent rapid consumption of spool space and should contact their
support resource for further assistance.

Copyright © 2011 Caringo, Inc.

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Version 2.6
February 2011