[DRBD-user] Performance with DRBD + iSCSI

Ross S. W. Walker rwalker at medallion.com
Wed Feb 21 17:14:08 CET 2007

Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.


> -----Original Message-----
> From: Leroy van Logchem [mailto:leroy.vanlogchem at wldelft.nl] 
> Sent: Wednesday, February 21, 2007 11:04 AM
> To: drbd-user at linbit.com
> Subject: Re: [DRBD-user] Performance with DRBD + iSCSI
> 
> 
> > Discover the latency for 1 block sized packet of data to 
> travel from one
> > host to another, say for a 4k packet.
> >
> > 24 packets transmitted, 24 received, 0% packet loss, time 23022ms
> > rtt min/avg/max/mdev = 0.164/0.226/0.290/0.038 ms, pipe 2
> > This is because each 4k io operation, the standard for file system
> > operations, needs to travel across the network. 
> >   
> Thanks for sharing this. If this proves to be useful, please include 
> this in the
> drbd documentation under section e.g.: expectations.
> 
> When I apply these to our cross linked e1000's: IOPS=3558 at 15MB/s.
> Why does normal O_SYNC i/o on ext3 using 0.7.23 top this by a factor 5
> or more? I thought 0.7.x did uses small bio's.

Explain the test procedure you used and your setup a little more and I
can get a better picture of your scenario.

-Ross

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