[DRBD-user] Opteron/Xeon - Kernel 2.4/2.6 setup

Helmut Wollmersdorfer helmut.wollmersdorfer at gmx.at
Mon Jun 14 14:26:24 CEST 2004

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

Lars Ellenberg schrieb:

> uhm, what does your cpu say to dd if=/dev/hda of=/dev/null ?
> or to dd if=/dev/zero of=scratchfile ?

root at via1:/mnt/nb0# dd if=/dev/zero of=scratchfile
2488220+0 Records ein
2488219+0 Records aus
1273968128 bytes transferred in 156,543794 seconds (8138094 bytes/sec)

CPU on via1 85-95%
CPU on via2 30-40%
(identical hardware on both nodes)

Here the CPU consumption seems to be the limit, or maybe ext3. With drbd 
full-sync I get 11.5 MB/sec -> 50% CPU on both nodes. Obviously drbd 
full-sync is _very_ efficient.

Do it reverse:

root at via1:/mnt/nb0# dd if=scratchfile of=/dev/zero
2488220+0 Records ein
2488220+0 Records aus
1273968640 bytes transferred in 25,523378 seconds (49913794 bytes/sec)

CPU 70%

Here the disk is the limit, 50 MB is identical to hdparm.

> this is most likely NOT drbd consuming cpu, but _tcp_ used by drbd...

Yes, drbd0 consumes the half directly.

> and might be reduced considerably by using NICs that do the tcp work
> themselves (and nic drivers that are aware of it).

Don't know.
# lspci -v
00:14.0 Ethernet controller: Advanced Micro Devices [AMD] 79c970 
[PCnet32 LANCE] (rev 36)
         Subsystem: Allied Telesyn International AT-2450 10/100 Fast 
         Flags: bus master, medium devsel, latency 32, IRQ 10
         I/O ports at e000 [size=32]
         Memory at df002000 (32-bit, non-prefetchable) [size=32]
         Expansion ROM at <unassigned> [disabled] [size=1M]
         Capabilities: [40] Power Management version 1

For my purposes the configuration is faster than needed. The hosted low 
traffic websites, 1 GB traffic per month, produce significantly below 
10% CPU.

> (and probably by using zero copy network writes as we do in 0.7)

Benchmark figures for the audience?

Helmut Wollmersdorfer

More information about the drbd-user mailing list