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Posts: 1,258 | Thanked: 672 times | Joined on Mar 2009
#33
Originally Posted by Konceptz View Post
I think this is somewhat pointless as the reason for striping was to use both hard drive's spin speed to increase data rate where the bottleneck is always the hard drive.

In this case, "conventional" seek time bottlenecks are eliminated due to the type of memory. Unless something is wrong with implementation, the default swap setup should be pretty much 100% of the speed you can get for "virtual memory".

But there are far more factors than "it should work this way". Therefore, if many people are coming up with a much faster swap solution by switching to a class 6 card, maybe we can also see if we can't pinpoint the slow down? (ie. throughput, kernel handling, etc..)
emmc/sd behave worse than a harddrive really...

The internal block size is something like 256k, if you write 4k (page size), then write 4K somewhere else, then the emmc/sd must internally read 256k, modify the 4k, write back 256k. This makes emmc/sd behave alot like a hard drive that hates seeks.

256 / 4 is 64, that is, worst case speed is the sequential write speed divided by 64. Or, in the case of a class 6 microsdhc card, the worst case speed is 96 kilobytes/sec.

Most swap activity is random I/O.

But anyway, even if this was not the case, striping across two devices doubles the bandwidth anyway.
 

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