Promise Technology TX8, TX4 user manual RAID 1 Mirroring

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UltraTrak100 TX4 and UltraTrak100 TX8 User Manual

RAID 1 – MIRRORING

When a disk array is mirrored, identical data is written to a pair of drives, while reads are performed in parallel. The reads are performed using elevator seek and load balancing techniques where the workload is distributed in the most efficient manner. Whichever drive is not busy and is positioned closer to the data will be accessed first.

With RAID 1, if one drive fails or has errors, the other mirrored drive continues to function. This is called Fault Tolerance. Moreover, if a spare drive is present, the spare drive will be used as the replacement drive and data will begin to be mirrored to it from the remaining good drive.

Figure A2. RAID 1 mirrors identical data to two drives

Due to the data redundancy of mirroring, the drive capacity of the array is only the size of the smallest drive. For example, two 1GB drives which have a combined capacity of 2GB instead would have 1GB of usable storage when set up in a mirrored array. Similar to RAID 0 striping, if drives of different capacities are used, there will also be unused capacity on the larger drive.

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Contents ULTRATRAK100 TX4 ULTRATRAK100 TX8 Copyright TrademarksImportant Data Protection Information Radio Frequency Interference Statement Table of Contents RAID Page Introduction Architectural DescriptionFeatures and Benefits Feature BenefitInstall Hard Drives ConfigurationGetting Started Unpack ULTRATRAK100UltraTrak100 Disk Drive Access TX4 Shown Connecting the Scsi Cables Back of UltraTrak100 TX4 see for TX8Daisy Chaining Several UltraTrak100s Together Connect Power Cable and Switch Power on Assign a Scsi IDConfigure the ULTRATRAK100 Press SEL to Save Changes Choosing a RAID Level Advantages DisadvantagesCharacteristics/Advantages Disadvantages RAID 0+1Partition and Format the Array JbodMaintenance Drive Status IndicatorsIndicator Color Meaning Critical & Offline ArraysREBUILDING/SYNCHRONIZING Fault Tolerant Arrays When a Disk Drive FailsReplacing a Disk Drive Module Drive Replacement Drive CarrierConnecting Cables to Disk Drive Replacing a Power Supply Module TX8 onlyBack of UltraTrak100 TX8 ULTRATRAK100 Front Panel Interface Type of Interface Name CommentsError Mode Configuration ModeLCD Messages Array FunctionalView Status Configure Array Configure Cache Configure ScsiView Status View Controller Info View Cache StatsView Array Information View EnclosureView Controller Information Temperature 30C/86F Array 0 Size 12GBRAID 0 Functional 5009 RPMCreate/Cancel Auto Array Setup Press SEL to Create Press Exit to Cancel What you can doView Drive Assignments Define Array Delete ArrayNo Free Disk What you can do Maxtor Asng In Ary IBM Asng In AryRAID Level 4KB 8KB Maxtor Free IBM Assigned Maxtor FreeWipe out disk Synchronize Array Disable Buzzer Array ID Rebuild/Sync Pri. LowWrite Cache Write Cache What you can doWrite Back Write Thru What you can do Write BackMode ID SelectedScsi ID Press Or to move these items on the LCD What you can doTechnical Support Services Contacting Promise SupportUSA Tech Support Center European Tech SupportPacific Rim Sales Office China OfficeLimited Warranty Disclaimer of Other WarrantiesPage Returning Product for Repair USA & Canada Your Responsibilities Appendix a Technology Background Introduction to RAIDRAID 1 Mirroring RAID 0+1 STRIPING/MIRROR RAID 3 Block Striping with Parity Drive RAID 5 Block and Parity Striping Jbod Spanning Appendix B Frequently Asked Questions Why can’t I see the drives on the UltraTrak100 under FDISK?