[DRBD-user] Significant performance improvement!

[Lars Ellenberg]

On Thu, Jun 19, 2008 at 09:28:58PM +0200, Marcelo Azevedo wrote:
> After placing the metadata on a different spindle (HD) , i was able to reach
> almost close to native speed (1-2MB/s less)
>  
> with metadata internal i was reaching tops around half of the native speed , 
> 37MB/s~ :
>  physical partition -> drbd -> ext3 
>   and
> 63MB/s~ with physical partition -> ext3 
> 61MB/s with  metadata  external, now this is true for another strong machine .
>  
> This other machine has hardware RAID1 with two :
> Cheetah T10 series,
> 146GB ,Serial Attached SCSI
> Interface Speed: 3Gb/s
> Spindle Rotation Speed: 15,000 RPM
> Performance: 10K
> on an IBM 2G Xeon server with 2 dual cpu packages , each cpu with 4 cores . IBM
> ServeRAID SCSI controllers
> 4GB of ram
> native speed  -hardware raid1 ->  physical partition -> ext3 is around 110MB/s
> ( still isn't this a bit slow for this HD ? )
> hardware raid1 -> physical partition -> drbd -> ext3 - 101MB/s with
> external metadata on a USB2 connected SATA HD 7,200 rpm
>  
> now this is the crazy part  - 8.3MB/s~ write speed ! with internal metadata ,
> and 150MB/s read speed..
> this test was repeated with bonnie , iozone and dd , all showed around same
> numbers ,
> i mean why the huge jump from 8MB/s to 100MB/s when using external metadata ,
> and should this be STRESSED on the Docs or when starting the program that
> putting the metadata on external media improves performance significantly?  ,
> still i don't understand why i was able to reach only 8MB/s write speed on this
> strong server , maybe because of the hardware raid1 underneath?

http://www.drbd.org/users-guide/ch-internals.html#s-metadata
 -> internal meta data 
   -> disadvantages

"head movements" aka seek time.

if you use internal meta data on the same single spindle,
without a decent battery backed write cache,
you want to configure a large-ish al-extents,
so drbd meta data updates happen infrequently.

-- 
: Lars Ellenberg                           http://www.linbit.com :
: DRBD/HA support and consulting             sales at linbit.com :
: LINBIT Information Technologies GmbH      Tel +43-1-8178292-0  :
: Vivenotgasse 48, A-1120 Vienna/Europe     Fax +43-1-8178292-82 :
__
please don't Cc me, but send to list -- I'm subscribed