How to decompress splited files (from one compressed one) located in different directories?

I have a problem in decompressing file in Ubuntu. Here, I have huge amount of compressed file (test.tar.gz) which is nearly 1.2 TB and resultantly becomes 3 TB after decompressing.

I have only 4 TB and 1 TB SSD so that I cannot decompress the file in a single SSD.

So, my point is;

1. How to split the (already) compressed file into several parts? (for example, splitting into 2 files, both of which are 600 GB)
2. After that, I have to locate those files into different directories due to the amount problem. Then, How to decompress those files into a single directory even if they are located at the different directories?

Use the split command :) If you want 2 files use -n with 2:

split test.tar.gz -n 2

Joining can be done with cat:

 cat x* > test2.tar.gz

will merge all files starting with x into test2.tar.gz Replace x* by the 2 files (and add directories).

Mind that you will need about double the space if all are on the same partition.

Split the tarball gzipped archive into two file and put one in the smaller SSD and the other into the bigger SSD; assuming your smaller SSD is mounted to /mnt/smallerSSD and the other SSD to /mnt/biggerSSD:

split -b 800M test.tar.gz test.tar.gz.part.
mv test.tar.gz.part.aa /mnt/smallerSSD
mv test.tar.gz.part.ab /mnt/biggerSSD

This will create two files test.tar.gz.part.aa and test.tar.gz.part.ab respectively of 800MB and about 400MB (sum is 1.2TB) and put them each in a different SSD. If you have less than 800MB of free disk space in your smaller SSD, use a smaller value.

Then, using cat and tar, proceed to extract the whole archive into the bigger SSD

cd /mnt/biggerSSD
cat /mnt/smallerSSD/test.tar.gz.part.aa /mnt/biggerSSD/test.tar.gz.part.ab | tar -xvz

This may not work if the free disk space is not enough; in that case you could use netcat/ssh to transfer (and then retrieve) some parts from the other devices in the local network, or else, you could use a more aggressive compression algorithm for your tarballs (e.g. bzip2) but this will result in longer compression/decompression times.