How to choose optimalarchiving settings
When creating a new archive, you are presented with several compressionrelated parameters onGeneral optionspage of "Archive name and parameters" dialog. First you need to selectthe archive format, which can beRAR,ZIP orRAR5. ZIP is preferable if you arenot sure that receiver of your archive has WinRAR or other softwareable to unpack RAR archives. Otherwise it is recommended to choose RAR,which supports more functions and higher compression. "RAR5" is the latestversion of RAR format introduced in WinRAR 5.0. While it includes manyimportant changes like AES-256 encryption, more efficient recovery record,larger dictionary sizes, older software including older WinRAR versionsis not able to decompress RAR 5.0 archives. So you need to takecompatibility issue into account when selecting RAR5 if you plan toprovide created archive to other people.
Regardless of the archive format the next step is selection ofcompression method. You can choose among "Store", "Fastest", "Fast","Normal", "Good" and "Best" methods. "Best" provides highest,but slowest compression, "Fastest" compresses poorly, but is very fast,"Store" adds files to archive with maximum possible speed, but withoutany compression. "Fastest" might be more suitable for daily backups,"Best" for Internet distribution, "Normal" for everyday use likecompressing email attachments.
If you selected the ZIP archive format, your preparations are finishedat this stage. In case of RAR and RAR5 there are two more important optionsaffecting compression: dictionary size and solid archiving mode.
Compression dictionary is the memory area used by compression algorithmto find and compress repeated data patterns. Larger dictionary frequentlyimproves compression of big files, especially in solid mode,but it also leads to slower compression and higher memory requirements.Normally we recommend to use 4 MB dictionary for RAR format and 32 MBfor RAR5 (RAR 5.0) archive format. You can read more about the dictionarysizehere.
"Create solid archive" option compresses files as single contiguous data stream resulting in higher compression ratio when processing manysmall similar files. But it also reduces speed of further archive modifications and increases amount of data loss in case of archive damage.This mode is explained in detailsSolidarchives topic.
These are all the main settings, which affect compression ratioand speed. Actually, you do not need to set them before every archiving.Simply select your favorite default values once in the defaultcompression profile, which can be createdinCompression settings dialog.