7.2.3 Caches and buffers

• IFS (incremental file system)
• IFS with several independent buffers
• Directory cache
• Data cache

Caches and buffers may be configured in the following sections. All file sizes are in MBytes. See "Setting up caches and buffers" on page 34 for a detailed description.

IFS (incremental file system)

This is a buffer that temporarily holds data copied to writable disks with operating system commands. To actually burn the buffered data to the disk a "cdadm writer flush" command must be issued. The incremental file system is described in "Burning disks incrementally" on page 154.
Example:

fsbuffer {
file { fsbuffer }
size { 100 }
inodes { 10000 }
}

The example defines a buffer of 100 MB. The file name of the buffer is fsbuffer. The maximum number of inodes (i. e., the number of files and directories that can be stored in the buffer) is 10,000.

IFS with several independent buffers

iXOS-JUKEMAN 2.3, in addition to setting up an IFS with one buffer, allows setting up several independent buffers. You select one of these buffers when you initialize a disk.
The section for these buffers is ifs { ... }. The parameter list { } specifies the names of all buffers (buffer names may be up to 15 characters). In the buffers section, the properties for each buffer are defined. The following parameters may be specified:

For example, to set up two buffers replace the fsbuffer { }section with the following section in server.cfg:

ifs {
list { small_buffer big_buffer }
buffers {
small_buffer {
file { small.buf }
size { 40 }
inodes { 10000 }
volumes { 20 }
}
big_buffer {
file { big.buf }
size { 800 }
inodes { 300000 }
volumes { 400 }
}
}
}

The example defines two buffers: small_buffer (40 MB) for up to 20 disks and 10,000 files/directories and big_buffer (800 MB) for up to 400 disks and 300,000 files/directories. When initializing a disk the corresponding buffer is specified in the following fashion:

cdadm writer fsi=ifs buffer=small_buffer action=init
location=jb.dev,5 vname=CDR_007

or

cdadm writer fsi=ifs buffer=big_buffer action=init
location=jb.dev,5 vname=CDR_007

Directory cache

This cache stores the directory names of the disks known to iXOS-JUKEMAN. See "The directory cache" on page 34 for a detailed description.
Example:

dircache {
file { dircache }
size { 100 }
}

The example sets up a directory cache of 100 MB. The file name of the cache is dircache.
If the line "file { dircache }" is omitted, the RAM cache size will be changed.

Data cache

This cache stores data read from the disks controlled by iXOS-JUKEMAN. See "The data cache" on page 38 for a detailed description.
Example:

regcache {
file { regcache }
size { 800 }
}

This example sets up a data cache of 800 MB. The file name of the cache is regcache.
If the line "file { regcache }" is omitted, the RAM cache size will be changed.