Areca 24/4 Internal/External Port Pcie 3.0 12 Gb/s SAS/SATA Raid Controller 2Gb Cache - Manual (Page 256)

APPENDIX
256
RAID 1 - Simple Mirroring
RAID 1-Simple Mirroring is also known as “two disk mirror”; data
written on one disk drive is simultaneously written to another
disk drive. Read performance will be enhanced if the array con-
troller can, in parallel, access both members of a mirrored pair.
During writes, there will be a minor performance penalty when
compared to writing to a single disk. If one drive fails, all data
(and software applications) are preserved on the other drive.
RAID 1-Simple Mirroring offers extremely high data reliability,
but at the cost of doubling the required data storage capacity.
HDDs and SSDs have different characteristics. If you combine an
SSD and a HDD in a RAID1-Simple Mirroring hybrid solution, you
can get all the reads from the SSD with SSD speed and at the
same time have the redundancy of RAID1 without the need to
buy a second, expensive SSD.