Re: Where does 130IOPS come from?

[Jan Schermer <jan@xxxxxxxxxxx>]

Every HDD has a “mean access time” number (related to the rotation speed, number of heads, etc.)

with 8ms access time this gives you 1000/8 = 125 seeks per second.

This is where it comes from :-)

Of course the best case will be better, I generally calculate 150 IOPS for any SATA drive, 200 for SAS. Some high-end FC disks with 15K RPM can have as high as 300 IOPS, but that’s probably not what we want to use here.

Jan

On 02 Jul 2015, at 17:53, Steffen Tilsch <steffen.tilsch@xxxxxxxxx> wrote:

Hello Cephers,

Whenever I read about HDDs for OSDs it is told that "they will deliver around 130 IOPS".
Where does this number come from and how it was measured (random/seq, how big where the IOs, which queue-dephat what latency) or is it more a general number depending on disk seek times?

Regards and thanks for clarifying,
Steffen

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