Striped RAID Very Sloooowwww

Striped RAID uses both drives at once. It doesn't fill one, then start on the other. When the drives are nearly full, adding a large file may be slow, since it may have to use many small pieces of the drives.

Mirrored RAID keeps identical copies on each drive. A file is written to both drives simultaneously, so the write speed is about the same a non-RAID. Read speed may be faster if the RAID software allows reading different blocks simultaneously from multiple drives.

Concatenated RAID combines multiple drives to look like one large virtual drive, using the actual drives in order. If you start writing from the beginning, the first drive will be filled, then the second, etc. The speed is the same as non-RAID. If you are dealing simultaneously with files that happen to be on different drives, it can be faster than non-RAID.

Striped RAID interleaves the drives to make a virtual drive. It is set up with a block size of one or more sectors. With two drives, the even numbered block are on one drive, the odd on the other. When a large file is written, pieces will be written to all drives simultaneously, so you get a higher read and write speeds.

How can you stripe performance if you are using an interface that doesn't even begin to support one channel per drive or have the bandwidth that one drive can deliver?

Also, Seagate firmware can affect small read/write I/O dramatically and make it slow.

The 300MB/sec is an SATA II specification for drives, but does not reflect real world performance. Like saying you have an Ultra160 / Ultra320 SCSI disk drive. The SCSI channel is what supports multiple drives. Or in SATA, Port Multiplier, when using a PM enabled controller and drive enclosure.

FireWire 800 is at best about what one drive today can deliver also, but still only a single bus/channel and close to what one drive alone can use.

Some dual drive cases have firmware to RAID the drives so it shows up as one volume, stripped or mirror.