User manual

Setting up iXOS-JUKEMAN
iXOS-JUKEMAN 2.2 User Manual Pre.12/9736
3.3 Set up caches and buffers
Caches speed up access to frequently used data. With iXOS-JUKEMAN
you can set up both a directory and a data cache. Caches on your hard
disk are not required to run iXOS-JUKEMAN, since it always holds a di-
rectory and data cache in RAM. For a large number of disks, however, it is
recommended to set up at least a directory cache.
In addition, iXOS-JUKEMAN supports incremental writing to disks with the
incremental file system. To use this feature, iXOS-JUKEMAN needs a
buffer on your hard disk to temporarily store the data to be written to the
disks. Using the incremental file system, it is almost as easy writing to op-
tical disks as writing to the hard disk.
Set-up of Recommendation
directory cache yes
data cache no (see “Note” on page 40)
IFS buffer required for incremental file system only
3.3.1 The directory cache
iXOS-JUKEMAN maintains a directory cache for all controlled disks. It
stores the directory structure and file name information in the cache. This
can improve performance, because a file search can be conducted with-
out having to insert disks into drives of a jukebox. The cache is cyclic: old
entries are dropped, when the cache is full and new entries arrive. The
default size for the directory cache is 1 MB in RAM. Depending on the
number of disks controlled by iXOS-JUKEMAN you may want to set up a
larger hard disk-based directory cache.
Because of sophisticated hash techniques, the directory cache offers ex-
ceptionally high performance.
The cache is filled dynamically, when clients access the server and re-
quest non-cached directories and files. Internally the caching occurs un-
der the following conditions:
1. If a directory is accessed and it is not found in the cache, then it is
filled into the directory cache.