[DRBD-user] Requested Feature

Lars Ellenberg lars.ellenberg at linbit.com
Tue Mar 18 14:24:45 CET 2008

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

On Tue, Mar 18, 2008 at 11:05:08AM +0000, Ben Clewett wrote:
> Dear DRBD,
> I would like to request a feature for DRBD.  I would be interested in 
> showing the data rate sent over the network to the other host in 
> /proc/drbd.  This would enable me to monitor bottlenecks and predict 
> limitations easily.

how about
# dstat -D total,sdf -N bond0,ethx0

> I am interested in knowing whether this is the sort of feature it would be 
> possible for a user like my self with a few years C experience to add my 
> self?  If so, whether any user might give me a pointer or two?

how shal we measure the data transfer rate?  if currently there is
nothing written, then there is nothing to transfer, data rate is zero.
probably not an indicator of any bottleneck.

or did I misunderstand the question?

> For instance, keeping an array of the last 15 minutes, holding a total of 
> data transfer in and out, so that a 1-minute, 5-minute and 15-minute rate 
> could be displayed, with the array rotated every new minute.

you can rrd graph the "dr/dw/nr/ns" counters.

> Please also let me know if this is a really bad idea!

I think the idea is good, but probably best implemented outside DRBD,
using available tools.  in-kernel re-implementation of the round robin
data base concept is somewhat "interessting" :)

> PS, another feature that would be very useful for me is another version of 
> /proc/drbd showing output as XML, say /proc/drbd_xml.

I don't think it is a good idea to export kernel data as xml.

> Then my self or other users could program our own extensions with
> ease.

what extensions are you thinking of?
what prevents you from implementing them now?

> A good DTD with comments could aid users tracking problems.

problems of which kind?
what sort of comments?

if anything, we can provide some wrapper (python, perl, whatever),
that would do
# proc_drbd_to_xml < /proc/drbd | xml_parsing_thingy
to give you a standardized xml representation of /proc/drbd.

but honestly, I don't quite see the benefit from that.

what am I missing, what is it you are after, really?

: 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 :
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