(original article)

Re: TODO list of Linux md/raid

11 June 2009, 19:37 UTC

Hi! I think, there is way to increase raid1 read performance on long files. Now raid1 read only from one disk, becose striping requied head seek. Solution in raid10 with "far" replicas also have disadvantages.

But we can use second (or third) disk to read ahead from curent request. For example, if get read request for blocks "ABCD", let it read to first drive, but also we can make requset to second disk (if there is no other request), read blocks "abcd" to read-ahead cache. Blocks "abcd" have offset from "ABCD". This mean, when long file will be readed, in the cache we can take all blocks from second drive. Value of this offset can be seted from /proc fs, or recalculated in dynamic. This method get double read performance without any changes in stored data.

What do you think about this algorithm? Artem Ryabov




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