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Storage basics: RAID striping in detail
By Stephen J. Bigelow
A SearchStorage.com reader recently asked: What is RAID striping?
Very simply, RAID striping is a means of improving the performance of large storage systems. For most normal PCs or laptops, files are stored in their entirety on a single disk drive, so a file must be read from start to finish and passed to the host system. With large storage arrays, disks are often organized into RAID groups that can enhance performance and protect data against disk failures. Striping is actually RAID-0; a technique that breaks up a file and interleaves its contents across all of the disks in the RAID group. This allows multiple disks to access the contents of a file simultaneously.
Instead of a single disk reading a file from start to finish, striping allows one disk to read the next stripe while the previous disk is passing its stripe data to the host system -- this enhances the overall disk system performance, which is very beneficial for busy storage arrays.
Parity can be added to protect the striped data. Parity data is calculated for the stripes and placed on another disk drive. If one of the disks in the RAID group fails, the parity data can be used to rebuild the failed disk. However, multiple simultaneous disk failures may result in data loss because conventional parity only accommodates a single disk failure.
Check out some of our recent expert advice on RAID striping and parity:
Storage expert Marc Staimer discusses the performance impact of RAID striping at the array and operating system level.
Designing storage for performance is a very esoteric effort by nature. There are quite a few variables that need to be taken into account.
RAID-50 combines striping with distributed parity for higher reliability and data transfer capabilities.
RAID-53 has a higher transaction rate than RAID-3, and offers all the protection of RAID-10, but there are disadvantages as well.
The difference between RAID-10 and RAID-01 is explained.
RAID, or redundant array of independent disks, can make many smaller disks appear as one large disk to a server for better performance and higher availability.
Stephen J. Bigelow is the features writer for SearchStorage.com
11 Apr 2007
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