Hi. I currently have 3 drives with data on them already, and one drive
that I just purchased. I am thinking of making this into RAID-5, but
was wondering if there was a way to do this while preserving the
existing data on the 3 drives that have data, without using external
storage?
Also, I was wondering if it is possible to make RAID-5 with more than
3 drives, for example, 5 drives and 1 parity?

Thanks in advance

Short answer: No. and No (at least, not as you describe it).

RAID 5 is a redundant array of inexpensive disks that puts its parity
stripe across all disks in the array. Its minimum recommended
configuration is 3 drives (I suppose you could make 2 drives work, but
it's kind of silly, IMO). Because RAID5 stripes across all drives, it
doesn't matter how many drives are in the array... The key is, though,
that all drives must be the same size. Also understand that the parity
stripe occupies one drive's worth of space, across the whole storage
array.

Had you already been in RAID5 configuration on a RAID controller that
allowed for expandable partitions, you could very well have added the
next drive to expand the array.

Nonetheless, not having that external storage method puts you in an
undesirable position if your drives happen to be subject to failure.

Well....you could technically create a RAID-5 using these drives...IF:

1.All 4 drives are the exact same size
2.There is little enough data that it could all fit on to a single one
of the 4 drives.

you could then copy all of the data from the 3 drives to 1 of the
drives so you end up with 1 drive with data and 3 empty drives,
connect everything to a RAID controller and create the RAID.

And yes parity is striped across all the drives in a raid-5 array so
that if any 1 drive goes down the data can be restored using the
remaining drives.

Hey give crythias-ga the answer he/she answered the question perfectly

Thanks for the kudos. I (male) am not a GA Researcher (name isn't
hyperlinked). Comment is free. :)