Neil Brown wrote: > On Monday May 7, rabbit@xxxxxxxxx wrote: >> Neil Brown wrote: >>> On Friday May 4, davidsen@xxxxxxx wrote: >>>> Peter Rabbitson wrote: >>>>> Hi, >>>>> >>>>> I asked this question back in march but received no answers, so here it >>>>> goes again. Is it safe to replace raid1 with raid10 where the amount of >>>>> disks is equal to the amount of far/near/offset copies? I understand it >>>>> has the downside of not being a bit-by-bit mirror of a plain filesystem. >>>>> Are there any other caveats? >>>>> >>> To answer the original question, I assume you mean "replace" as in >>> "backup, create new array, then restore". >>> You will get different performance characteristics. Whether they >>> better suit your needs or not will depend largely on your needs. >> Hi Neil, >> Yes I meant take an existing 2 drive raid1 array (non bootable data) and >> put a raid10 array in its place. All my testing indicates that I get the >> same write performance but nearly double the read speed (due to >> interleaving I guess). It seemed to good to be true, thus I am asking >> the question. Could you elaborate on your last sentence? Are there >> downsides I could not think of? Thank you! > > I would have thought that you need "far" or "offset" to improve read > performance, and they tend to hurt write performance (though I haven't > really measured "offset" much). > > What layout are you using? > Correct, I am using 'far' layout. The interleaving of the 'offset' layout does not work too good for sequential reads, but far really shines. Yes write performance is hurt by about 10%. Compared to 190% gain in reads I can live with it. - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
