[DRBD-user] Performance with DRBD + iSCSI

Leroy van Logchem leroy.vanlogchem at wldelft.nl
Wed Feb 21 17:04:07 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.

> 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.

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