About RAID-0 with 4 HDDs

are you using OS X to manage this or something else?

https://www.softraid.com/

SoftRaid will support 4 drives as RAID 0 and there is a free trial.

I don't want to put a SSD as it's not officially supported

Nonsense. Apple used to sell 3.5-in form factor SSDs to mount on a drive sled, but they no longer do.

You can use a 2.5-in form factor drive, but you need a sled adapter.

All those items you describe use ONE large file, and do not intersperse raids or writes to other files. Of course they were fast, because they are not a "Real-World" test of actual use for production.

You do not need Striped RAID for more space one logical drive.

Use "Concatenated RAID" for more space. It is also called "Just a Bunch of Drives" or JBOD. Its advantage over Striped RAID is that if a Drive fails, its files can still be saved with Data Rescue Utilities.

"Concatenated RAID" can be used with two or any larger number of drives. The drives can be very different from each other. It should be directly available in the version of Disk Utility you are running.

Whats the advantage of two raid 0's in your device? FWIW the cost of two drives you could probably get an SSD, hat would be far faster and with RAID 0 if you loose one drive you effectively made the other drive dead as well. You are also dependent on a software solution - if it's Apple or 3rd party and you are running 10.7 and get into a mess no one is going to support your platform.

This card for RAID it's only for more performance and more support for RAID (more types of RAID) or it's necessary for mroe than two HDDs?

Striped RAID requires frequent backups, because if EITHER Drive fails, ALL data is lost. Recovery Software can not deal with half the blocks being written to a different drive, and because Striped RAID has no redundancy, there is no way to recover that data.

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RAID gets its speed boost when reading the second and subsequent blocks from the SAME very large file. Allowing ANY intervening reads to or from any other files completely ruins that speedup.

You should not expect a speedup when you place both your Source and Destination files on the same RAID set. Each reference to a different file destroys the speedup from RAID.

You must not use a RAID set used for fast production data transfers for your Boot Drive, because the Boot drive is constantly reading and writing to dozens of different files all over the drive, and the RAID performance will be lost.

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There is NO performance advantage to Hardware RAID for Striped RAID or mirrored RAID. The RAID card is only required for RAID 5, and similar RAID versions that compute checksums and store them on the last drive in the set.

The Apple RAID card has a battery on board, so that once the data are delivered to the RAID card, the processor is signaled that the data are safe and it can continue. Then the checksums are computed and written to the drive. Without the battery, the processor must WAIT for the checksums to be computed and stored on the drive before proceeding, so performance will be lower. And the batteries on those cards have been hard to find and nothing but trouble.

RAID really boosts the data transfer, I can see it.

How did you make that measurement? with ONE Large data file? or a disk test that uses ONE large data file?

But I want to know if I can or not to use 4 HDs with software-RAID being RAID-0, sure. It will crash or it supports,

It will not crash. But it makes NO SENSE. you need TWO RAID sets, not one large one RAID set to get performance. One is Source, one is Destination. Scratch, Libraries, and Boot Drive go on other drives.

I had only one HD and it fails I would lose data too,

The difference is that EITHER drive failing wipes out BOTH. Even with very reliable drives, you are cutting the Mean Time Between Failure in half with two drives, and cutting in 4 with four drives. You will need backups at least daily, or you will need to not leave ANY finished output files on these drives.

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You should add a USB-3 card in the PCIe slot on your Mac and use some Fast USB drives as well.