Re: rbd speed: write vs read

[Fyodor Ustinov <ufm@ufm.su>]

On 05/06/2011 07:08 PM, Sage Weil wrote:
> On Fri, 6 May 2011, Fyodor Ustinov wrote:
>> Hi!
>>
>> oops. This my misconfiguration.
> Out of curiousity, what was the misconfiguration?
I have 20 OSD server. 10 in one vlan and 10 in other (btw, question: mon 
server can listen on all ip addressessimultaneously?).
Because our NOC, 10 servers have anisotropic configuration - 800Mbps in 
one direction and 150Mbps to another.
> Doing a streaming read in 10MB chunks when RBD is striped over 4MB
> objects won't be terribly efficient.  You should get the best sync read
> performance when the object sizes match up.  You'll get better performance
> if whatever is sitting above the block layer dispatches multiple read
> requests in parallel (i.e. something smarter than dd, like a file system).
Hmm. But it's linear read. I do not know how it works internally, but 
did reading 10MB by 4MB chunk can not be executed in parallel?

WBR,
     Fyodor.