[DRBD-user] huge performance problems, drbd8 sync painfully slow

Juergen Sauer juergen.sauer at automatix.de
Sat Mar 30 15:48:36 CET 2019

Am 29.03.19 um 16:28 schrieb Digimer:
> Sync performance is not DRBD performance. In fact, the faster sync is
> forced to go, the more it takes away from application performance that
> is using DRBD. By default, DRBD 8.4+ will watch the load coming in from
> above and dynamically adjust the sync performance, speeding up when load
> is light and slowing down when load is high.
> Lets say, for simple math, your DRBD resource has a max sustained write
> speed of 100 MB/sec. If Sync is running at 35 MB/sec, you've got only 65
> MB/sec left for your applications. If you force sync to 90 MB/sec, only
> 10 MB/sec is available for your application. (Obviously this is
> simplistic and doesn't touch on IOPS, but you get the idea I hope).

Not Agreed.

But avaible is about 350 MiB/sec on device, and about 1100 MBit/sec over
dedicated drbd 10GBe clusterlink.

So 30 MiB/sec is painfully a waste of time.

> If you want to see what DRBD write performance is like in the real
> world, pause the sync (or wait for it to finish), then try running write
> tests. If that's slow, then we have a real problem.

> In the meantime, I'd highly recommend simplifying your drbd config.
> Premature optimization never is.

OK, what makes the performance better?

mit freundlichen Grüßen
Jürgen Sauer
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