[DRBD-user] Discarding device blocks very slow

Eric Robinson eric.robinson at psmnv.com
Mon Jul 31 11:32:50 CEST 2017

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


For what it's worth:

1. Discard is enabled and working on both nodes.
2. No messages about trim or discard in the logs.
3. Network latency is sub-1 millisecond, bandwidth is 1 Gbit (utilization about 10%). 
4. Drbd is version 9.0.8 on both nodes.

--
Eric Robinson
   

> -----Original Message-----
> From: drbd-user-bounces at lists.linbit.com [mailto:drbd-user-
> bounces at lists.linbit.com] On Behalf Of Robert Altnoeder
> Sent: Monday, July 31, 2017 2:17 AM
> To: drbd-user at lists.linbit.com
> Subject: Re: [DRBD-user] Discarding device blocks very slow
> 
> On 07/31/2017 10:46 AM, Eric Robinson wrote:
> > But that still does not explain why discards across the network are so slow.
> 
> There are lots of possible reasons.
> Discard might not be enabled on both nodes, there should be a message
> about discard being available or unavailable in the logs. IIRC, if it can't discard,
> it will zero-out.
> The network may have too high latency or too low bandwidth.
> Without a great amount of detailed information all one can do about
> performance-related issues is to guess.
> 
> Generally, both nodes should be running the same and most recent version
> of DRBD 9, because all those features have been added quite recently, and
> lots of enhancements and fixes are still applied to the code.
> 
> --
> Robert Altnoeder
> +43 1 817 82 92 0
> robert.altnoeder at linbit.com
> 
> LINBIT | Keeping The Digital World Running DRBD - Corosync - Pacemaker f /
> t /  in /  g+
> 
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