7.7.2 Specifying the types of cache files and their storage locations

If you will be using disk caches or two-way caches, specify the storage locations for the files that will store the cache information.

A file storing cache information is called a cache file.

When you will be using disk caches or two-way caches, you must specify the storage locations for the cache files.

Organization of this subsection

(1) Types of cache files
(2) Specifying storage locations for cache files
(3) Relationship between storage locations for cache data files and EADS servers when redundant copies of data are created

(1) Types of cache files

The following subsections describe the three types of cache files.

(a) Cache data file

Cache data files store data (keys and values) that are stored in caches.

(b) Cache index file

Cache index files store indexes for the data in cache data files.

As many cache index files are created as there are cache data files.

(c) Cache information file

Cache information files store settings for caches.

One cache information file is created for each cache.

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(2) Specifying storage locations for cache files

In this subsection, you specify storage locations for cache files.

You must specify storage locations for cache data files. The following table lists the storage locations for cache files.

Table 7‒9: Storage locations for cache files and the file names
No.	Type of cache file	Storage location	File name
1	Cache data file	`directory-specified-in-the-eads.cache.disk.n.dir-parameter-in-the-cache-properties/cache-name`	`eads_data_[EADS-server-ID]_[cache-name]_[range-ID]_[nnnnn].ecf`
2	Cache index file	`directory-specified-in-the-eads.cache.disk.info.dir-parameter-in-the-cache-properties/cache-name`	`eads_index_[EADS-server-ID]_[cache-name]_[range-ID]_[nnnnn].ecf`
3	Cache information file	`directory-specified-in-the-eads.cache.disk.info.dir-parameter-in-the-cache-properties/cache-name`	`eads_info_[EADS-server-ID]_[cache-name].ecf`

Legend:

[range-ID]: Number (integer 01 to 96) used to identify a range in a cache. The range ID matches the server ID of the EADS server on which the data is stored.

[nnnnn]: Sequential file number (five-digit integer)

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(3) Relationship between storage locations for cache data files and EADS servers when redundant copies of data are created

Specify as many storage locations for cache data files as the multiplicity value specified in the eads.cache.disk.n.dir parameter. For example, if the number of redundant copies of data plus the original is set to 3, specify a value from 1 to 3 for n.

The following explains the relationship between storage locations for cache data files and EADS servers when the number of redundant copies of data plus the original is set to 3, using EADS server 1 as an example.

Figure 7‒5: Relationship between storage locations for cache data files and EADS servers

Because data is distributed in EADS, cache data files are stored in each EADS server.

The following cache data files are stored on EADS server 1:

Cache data file that stores data in range 1 (original data)
Cache data file that stores a copy of data in range 4
Cache data file that stores a copy of data in range 5

Specify the storage locations for these cache data files in the eads.cache.disk.n.dir parameters in the cache properties.

Example specification of the eads.cache.disk.n.dir parameter (when using the same directory to manage the cache data files):

eads.cache.disk.1.dir=/hdd/cache_server01     # Storage location for the original data
eads.cache.disk.2.dir=/hdd/cache_server01     # Storage location for the data in range 5 (copy 1)
eads.cache.disk.3.dir=/hdd/cache_server01     # Storage location for the data in range 4 (copy 2)

Example specification of the eads.cache.disk.n.dir parameter (when using different directories to manage the cache data files):

eads.cache.disk.1.dir=/hdd/cache_server01_range01     # Storage location for the original data
eads.cache.disk.2.dir=/hdd/cache_server01_range05     # Storage location for the data in range 5 (copy 1)
eads.cache.disk.3.dir=/hdd/cache_server01_range04     # Storage location for the data in range 4 (copy 2)

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