rbd speed: write vs read

rbd speed: write vs read

[Fyodor Ustinov]

Hi!

oops. This my misconfiguration.

WBR,
     Fyodor.

Re: rbd speed: write vs read

[Sage Weil]

On Fri, 6 May 2011, Fyodor Ustinov wrote:
> Hi!
> 
> oops. This my misconfiguration.

Out of curiousity, what was the misconfiguration?

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).

sage

Re: rbd speed: write vs read

[Fyodor Ustinov]

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.

rbd speed: write vs read

[Fyodor Ustinov]

Hi!

root@stb1:~# dd if=/dev/zero of=/dev/rbd0 bs=10240000
^C13217+0 records in
13217+0 records out
135342080000 bytes (135 GB) copied, 1135.75 s, 119 MB/s

root@stb1:~# dd if=/dev/rbd0 of=/dev/null bs=10240000
^C930+0 records in
929+0 records out
9512960000 bytes (9.5 GB) copied, 394.773 s, 24.1 MB/s

It's my misconfiguration?

P.S. 20 OSD servers, 2*1G ether.

WBR,
     Fyodor.