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Re: DRBD sync speed




On Wed, Oct 10, 2018 at 12:38:57PM +0100, Adam Weremczuk wrote:
> I have 2 identical servers connected with 2 x 1 Gbps links in bond_mode
> balance-rr.
> 
> The bond is working fine; I get a transfer rate of 150 MB/s with scp.
> 
> cat /proc/drbd
> version: 8.4.10 (api:1/proto:86-101)
> srcversion: 17A0C3A0AF9492ED4B9A418
>  0: cs:SyncSource ro:Primary/Secondary ds:UpToDate/Inconsistent C r-----
>     ns:10944 nr:0 dw:0 dr:10992 al:8 bm:0 lo:0 pe:0 ua:0 ap:0 ep:1 wo:f
> oos:3898301536
>     [>....................] sync'ed:  0.1% (3806932/3806944)M
>     finish: 483:25:13 speed: 2,188 (2,188) K/sec
> 
> The transfer rate is horribly slow and at this pace it's going to take 20
> days for two 4 TB volumes to sync!
> 
> The volumes have been zeroed and contain no live data yet.
> 
> My sdb disks are logical drives (hardware RAID) set up as RAID50 with the
> defaults:
> 
> Strip size: 128 KB
> Access policy: RW
> Read policy: Normal
> Write policy: Write Back with BBU
> IO policy: Direct
> Drive Cache: Disable
> Disable BGI: No
> 
> Performance looks good when tested with hdparm:
> 
> hdparm -tT /dev/sdb1
> 
> /dev/sdb1:
>  Timing cached reads:   15056 MB in  1.99 seconds = 7550.46 MB/sec
>  Timing buffered disk reads: 2100 MB in  3.00 seconds = 699.81 MB/sec
> 
> The volumes have been zeroed and contain no live data yet.
> 
> Any idea why the sync rate is so painfully slow and how to improve it?

Have you read
https://serverfault.com/questions/740311/drbd-terrible-sync-performance-on-10gige

and edited your drbd.conf to suit?

Unrelated: how is it that you decided on RAID50 for 4TB of disk space?
If it's valuable, you should be looking at RAID10. If it's not
valuable, why 50 over 6 or RAIDZ2 or 3?

-dsr-