Comment Re:I call BS (Score 2) 184
RAID controllers do not launch reads on all involved drives. That would be stupid.
?
For a RAID1, most RAID controllers (and software RAID implementations) will absolutely read from all devices so as to service the read ASAP.
For distributed parity forms of RAID, you inherently have to read from all devices.
For dedicated parity disk forms of RAID, you have to read from all devices except the parity device.
I've never tried a mixed RAID1 of SSD and magnetic disk, but with a large enough write cache the theory seems reasonable. Most controllers [with a BBU] acknowledge the write as soon as it hits cache.