Module Three

N frds provides the ability to reconstruct the

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n FRDS : provides the ability to reconstruct the contents of a failed disk onto a replacement disk. n Enables the continuous monitoring of these parts and the alerting of their failure n FRDS+ n Protect from disk failure – can reconstruct disks by automatically hot swapping while server is running n Includes environmental n FRDS+ adds hazard warnings RAID Levels RAID 0 (STRIPPING) n Creates one large disk by using multiple disks – striping n No redundancy n No fault tolerance (1 fail = all fail) n Read/Write performance is increased
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RAID 1 (MIRRORING) n Mirroring n Duplicates data on other disks (usually one to one ratio) n Expensive (doubles cost of storage) RAID 2 (HAMMING CODE PARITY) n Multiple disks n Parity information created using a hamming code n Can be used in 39 disk array 32 Data and 7 recovery n Not used, replaced by more flexible levels RAID 3 (BYTE LEVEL PARITY) RAID 4 (BLOCK LEVEL PARITY) n RAID 3 – Byte level n RAID 4 – Block level n Stripe across multiple drives n Parity information on a parity drive n Provides redundancy n Can affect performance with single parity drive RAID 5 (INTERLEAVE PARITY) n Most popular n Stripes data and parity information across all drives n Uses interleave parity n Reads and writes performed concurrently n Usually 3-5 drives. If one drive fails, can reconstruct the failed drive by using the information from the other 2. RAID 7 (SINGLE VIRTUAL DISK) n Functions as a single virtual disk n Usually software over Level 5 hardware n Enables the drive array to continue to operate if any disk or any path to any disk fails. RAID Summary 0 – Striping 1 – Mirroring 2 – Hamming code parity 3 – Byte level parity 4 – Block level parity 5 – Interleave parity 7 – Single Virtual Disk Other Types of Fault Tolerance Redundant Servers n Primary Server mirrors to secondary server n Fail-over or rollover to secondary in the event of a failure n Server fault tolerance can be warm or hot Server Cluster n Group of independent servers managed as a single system n Load Balancing n Improves performance n “Server Farm” n Microsoft Cluster Server
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Backup Methodologies Full Back Up – every file Incremental n Only files that have been changed or added recently n Only files with their archive bit set are backed up. n This method is fast and uses less tape space but has some inherent vulnerabilities, one being that all incremental backups need to be available and restored from the date of the last full backup to the desired date should a restore be needed. n Restore = last full backup plus each incremental Differential n Only files that have changed since the last backup n All files to the full backup (additive) n Restore = full backup plus the last differential Types of Tape n DAT – Digital Audio Tape n QIC – Quarter Inch Cartridge – Small and slow n 8mm Tape – Superceded by DLT n DLT – Digital Linear Tape – 4mm tape – large and fast Other media CD – permanent backups, longer shelf life than tape
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n FRDS provides the ability to reconstruct the contents of...

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