From SigmonSays

RAID, RAID/md

Contents 1 Summary 2 Space Calculations 3 History 4 Current Status 5 see also

Summary

Generation	Disk Size/Count	Total Raw Capacity	Formatted Capacity	Notes
1st, grapefruit	4x 250G IDE	1TB	691G
2nd, papaya	5x 500GB SATA	2.5TB	1.8TB
3rd, watermelon	5x 1TB SATA	5TB	3.6TB
4th, pineapple	TBD

Space Calculations

ext2/3 file system overhead claims to be 10% of available raw capacity. ie, RAID5 Configuration for 3rd generation `watermelon` setup:

TOTAL_DRIVES=5
PARITY_DRIVES=1
DRIVE_SIZE=1000 # GB

RAW_CAPACITY = DRIVE_SIZE * (TOTAL_DRIVES-PARITY_DRIVES)
FS_OVERHEAD = RAW_CAPACITY * 0.10
FORMATTED_SIZE = RAW_CAPACITY - FS_OVERHEAD

RAW_CAPACITY
FS_OVERHEAD
FORMATTED_SIZE

NOTE RAW_CAPACITY is available space w/o a file system (N-1)

History

• RAID V1 - 4x 250GB, Maxtor drives IDE
• RAID V2 - 5x 500GB, Seagate Barracuda 7200.10 ST3500630AS 500GB Serial ATA 7200RPM Hard Drive w/16MB Buffer
• RAID V3 - 5x 1TB, Seagate Barracuda 7200.11 ST31000333AS 1TB 7200 RPM SATA 3.0Gb/s 3.5" Internal Hard Drive -Bare Drive
• RAID V4 - research phase
• RAID V5

Current Status

• http://sigmon.homelinux.net/raid

see also

• mdadm