RAID 1 (Mirroring and Duplexing) Comparing mirroring and duplexing Mirroring is the simplest method of avoiding data loss when a single disk fails. During writes, data is sent to both disks. During reads, different data can be read from both disks, which provides good read Performance. Duplexing is another form of keeping a copy of data. Where mirroring uses a single controller, duplexing can also handle a controller failure. Duplexing requires an operating system that supports RAID 1.
This site says cost of tiling per square metre is between $95 and $170 psm for floor tiles and $90 and $160 for wall tiles. Those prices include tiles so take $30 psm off those.
Slate wall tile costs $3.78 per square foot. Marble varieties of floor tile are readily available at an average of $6 per square foot, and polished marble wall tile can be found at $10.90 per square foot. It can also be purchased in half square-foot pieces (6 inches by 6 inches) at $713 for eight pieces.