Page Comparison

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(*) Guess based on various hardware review site tear-downs.

Read Performance: Random 8MB reads

This experiment targets recovery -- how quickly can we read 8MB segments from the disk?

The result is boring -- all disks can average between 260 and 270 MB/s (which is apparently about all we can expect of our 3Gbps SATA ports).

-TODO- 8MB latency may be interesting. If we have lots of nodes, we may only read a few segments. Hopefully that offers just as good bandwidth as reading a lot of them.

Write Performance: Random 8MB writes to some fraction of the disk

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The idea is to test how well write performance holds up under increased space utilisation. For example, if we write 120GB to the first 20% of the disk's logical blocks (randomly overwriting), how does the drive fare? We'd hope that when utilisation isn't too high, the drive's FTL would be able to efficiently erase recently overwritten LBAs and keep up with the write load.

Before each run, the disks were trimmed using hdparm. Perhaps a secure erase would have been better, but most drives appeared to regain full write performance this way. Notably, the Mushkin one did not (the 100% test was first, followed by 20,40,60%...).