Development > PowerArchiver 2017 – data deduplication, fma-rep1 filter (.pa)

PowerArchiver 2017 – data deduplication, fma-rep1 filter (.pa)

February 7th, 2017 | Category: Development

Dear users,

We have exciting additional information about PowerArchiver 2017 and its advanced codec pack – the .pa format. We have added a very important new feature, a data deduplication filter called fma-rep1. It helps in achieving significantly better compression on huge files and is quite unique among our commercial peers.

What is fma-rep?

The Deduplication filter(fma-rep1) is based on anchor hashing ((also known as content-based segmentation). Technically, it is LZ77, but has no entropy coding and only longer matches have a chance to be replaced with a reference.

It has much lower memory requirements than plzma4, so it can be used to compensate plzma4’s smaller window/dictionary size. It is also very fast, between 50 MBs and 100 MBs (real life with SSD), depending on your cpu (single threaded), so we can use it in both our optimized strong and optimized fast modes.

Due to large file sizes, and the fact that fma-rep takes a lot less memory than plzma4, it is very useful for large software installation DVDs that have a lot of compressed data already. The most efficient way of using it is to use a large window of fma-rep1 and fast codec to achieve good compression and yet very fast speed.

Example

For test examples, we selected the popular Microsoft installation ISO file for their Office 2016 software. You may download the trial installation file yourself so that you may check the compression and speed results on your own computer. Due to the large sizes of the installation files and their internal contents, slower compression codecs found in WinZip (zipx, lzma), WinRar (rar5, best), 7-zip (lzma2, ultra) as well as our own plzma4, do not significantly help the compression ratio. So in this scenario, we can use the Optimized Fast mode and get 3x faster compression while still getting great compression ratio compared to others.

PowerArchiver 2017 with Advanced Codec Pack (.PA) is available to our most dedicated users with an active PowerArchiver Select plan, as a preview version. First public releases will come in February 2017.