On May 18, 2010, at 3:36 PM, Nelsn Helm wrote: > Can a single HD (physical disk) be formatted into a GUID volume and a Mac OS > extended volume?
Don't confuse the partition map scheme with the volume format! The partition map chops the disk into one or more volumes. You must then format these partitions. In disk utility you can choose one of several formats. There are four different flavors of Mac OS Extended (also called HFS+), MS-DOS and UFS. If the drive is going to be used on a Mac, you should probably choose the journaled Mac OS Extended. This can be read on any Mac. In older parlance, laying down the partition map was called initializing and installing a file system was called formatting. > Yes, but I keep all my data on external drives, and I want them to be > readable by PPCs. If you format partitions with journaled Mac OS Extended any Mac can read them no matter what partitioning scheme is chosen. It's only when booting that you have to worry about the partition mapping type. > I just "surface scanned" my main external HD, all my data but pictures. It > has 1,500 bad blocks. I have always backed it up, but back-ups don't protect > from data loss from bad blocks on the mother disk. If I read it right, RAID 3 > or higher stores data three places, two mirror images and one to compare > those images, looking for differences indiciative of errors. RAID 3-5 all use at least three disks with two for data and one for parity. For example, if you have three 1G disks in a RAID 3 array, the capacity of the array will be 2G because one of the disks is devoted to parity. The parity storage allows the content of either data disk to be reconstructed after a failure using checksums.
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