[DRBD-user] Minimum/recommended system requirements

Helmut Wollmersdorfer helmut.wollmersdorfer at gmx.at
Tue Apr 19 17:42:13 CEST 2005

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


Chris de Vidal wrote:

> So my question: do our boxes meet the minimum/recommended spec?  Both are
> identical:
> DRBD 0.7.10
> CentOS 3.4 (same as RedHat Enterprise Linux 3)
> Celeron 600
> 1GB ECC RAM
> 120GB drives (don't recall the DMA/RPM speed but I can find out if necessary)
> 100MBit Intel NICs connected by crossover (don't recall which chipset but
> I can find out if necessary)

This should be appropriate for DRBD, but maybe not enough for the 
additional applications.
I am running EPIAs at 600 MHz (~Celeron 500), 512 MB, 80+160 = 240 GB, 
100 Mbit NIC, very fine with DRBD.

> If they do meet spec, any ideas why load peaked so much?  I was writing
> many small files using dump and restore.  I could see how someone could
> DoS us by repeatedly hammering our logs or uploading thousands of tiny
> files.

DRBD adds only little use of RAM and CPU, but it adds traffic on the 
NICs. Some NICs with bad hardware or bad drivers produce reasonable 
CPU-usage at full traffic.

Most resource comsumption comes from the applications at top of DRBD. 
Compare benchmarks of DRBD-sync against a large 'cp -a <something>' on 
ext3/DRBD.

> P.S. I just had a thought: perhaps I need to run hdparm.

If your HDDs run with UDMA 133 you should get read speeds over 50 MB/sec 
with 'hdparm -tT /dev/hdx. Second thing is to measure network speed, 
e.g. with 'bing <own-IP> <peer-IP>.

Helmut Wollmersdorfer



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