RAID (p.7)

RAID Wrapup

So the RAID levels are protocols for managing an assortment of hard disks and presenting them to the system as one drive. Advantages offered are increased data safety, increased read/write performance, and increased size of contiguous space. Of course the main tradeoff in those schemes using mirroring or parity, or both, is space for safety. Some storage space is sacrificed to insure the survival of the data as a whole. This general table summarizes the relationships.

You may be wondering what happened to RAIDs 2 and 4. What we have covered here are the levels in most common use. RAID 2 is intended for drives which do not have built-in error detection. RAID 4 is much like RAID 3, with a dedicated parity drive and data striped across more than one drive. The difference is that RAID 4 stripes data in larger blocks, rather than at byte level. Reads are quite fast, but writes are slow.

Link

For an excellent article about RAID and RAID systems, see: http://www.systemlogic.net/articles/01/1/raid/

More to Come

Watch this EPC Newsletter! More cost-effective IDE RAID solutions are slated to join Advantech's PCM-3900 IDE RAID controller in the first quarter of 2002.

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