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Persistent data » History » Revision 5

Revision 4 (Greg Burri, 07/21/2009 01:33 PM) → Revision 5/18 (Greg Burri, 07/30/2009 04:29 PM)

h1. Structures 

 h2. Files cache 

 This file contains all the shared files and theirs SHA-1 hashes. This file is saved in user space after an update of the file list, it is completely loaded at the start of Aybabtu. If some paths of some files doesn't match the shared directory they are discarded. 

 You can see the proto file here : source:/protos/files_cache.proto 

 h3. Size 

 Here is a size approximation for 50'000 files stored in 1 TB. The overhead of the file format is not taken in account. 

 <pre> 
 Nb of files : 50'0000 
 Total size : 1 TB 
 Chunk Size : 32 MB 
 Average file per directory : 50 
 Average filename and dirname length : 50 char 
 Size of a hash : 20B 
 </pre> 

 <pre> 
 AverageFileSize = 1*1024^4 / 50'000 = 21MB 
 Sha1Size = floor(AverageFileSize / 32MB) * 20 * 50'000 = 1 * 20 * 50'000 = 977kB 
 FilenameSize = 50'000 * 50 * 2 = 4.8MB (2 bytes per char) 
 DirnameSize = (50'000 / 50) * 50 * 2 = 97kB 

 TotalSize = 977kB + 4.8MB + 97kB = 5.9MB 
 </pre> 


 h2. Configuration file 

 TODO..