IBM Spectrum Virtualize V7.6 introduced advanced RAID technology known as "IBM distributed RAID", that improves the RAID array performance. IBM distributed RAID (DRAID) technology provide up to 20% better I/O performance and up to 10 times faster array rebuild rate compared to traditional non-distributed RAID arrays. (Please note that multiple enhancements for DRAIDhave been included in the later releases of IBM Spectrum Virtualize software).
In case of traditional RAID arrays, the hot spare disk drives are idle and do not perform any operation until one of the array member drive fails. Also, the rebuild operation takes longer time because it is limited by the time taken to write an entire disk drive. Hence the rebuild operation also increases the load on other member disk drives which increases the probability of second drive failure.
IBM distributed RAID array technology addresses these limitations by distributing the spare capacity over specific rebuild areas across all member drives. Hence in case of a member drive failure, the rebuilt data can be copied faster to the rebuild areas and redundancy is restored much more rapidly. Thus, the rebuild times are dramatically reduced, which lowers the extra load on the member drives. After the failed drive is replaced, data is copied back to that drive from the distributed spare capacity.
IBM distributed RAID has many advantages over traditional RAID. It includes additional functions and features. Few of the features are as follows:
- BM distributed arrays allow to create much larger RAID arrays. They can manage 4 to 128 disk drives and contain their own rebuild areas that can be used to store rebuild data when drives fail.
- Ability to distribute not only the spare space but also data and parity strips among more drives than in traditional RAID. This means more drives can be used to create one array, and therefore,
improving performance of a single array.
- Supported distributed array types are RAID 5 and RAID 6.
- Traditional and distributed arrays can co-exist in the same pool.
To know more about the features and advantages of IBM distributed RAID technology, you can refer to IBM DRAID whitepaper available at https://www.ibm.com/common/ssi/cgi-bin/ssialias?htmlfid=TSW03521USEN&.
This whitepaper is intended for customers looking for IBM Distributed RAID array technology to configure internal storage on IBM Spectrum Virtualize range of products. It also provides guidelines to move the existing volumes from traditional RAID arrays to the distributed RAID arrays that improves the array performance especially during array rebuild operations resulting due to drive failures.
For more information refer IBM Knowledge Center http://www.ibm.com/support/knowledgecenter/search/DRAID.
Please note that these are my personal thoughts and do not necessarily represent that of my employer.
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