[DRBD-user] Sync its so slow

Nate Seif seifn at rstechnicalservices.com
Tue Oct 23 20:52:33 CEST 2007

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


Identify where the bottleneck is to [possibly] get faster sync speeds:
(1) Check to make sure your kernel has proper [driver] support for your 
chipset. Run 'lspci' to get info about what chipset you have if you don't 
already know.
(2) Make sure you have DMA enabled for your hard drives. Research first, 
then run 'hdparm' to test write speeds to see if hard drives are the 
bottleneck.
(3) Check your network: can you get faster transfer speeds with other 
app's? Make sure you've got the proper drivers for your NIC's...

Good luck.

Nate


On Tue, 23 Oct 2007, Igor Neves wrote:

> Hi,
>
> I'm having problems with sync, using drbd 8.0.4, in centos 5.0.
>
> When i have to do one full sync, of the disc, it takes me 12 Hours
> (500G).
>
> The 2 nodes are connected between Gigabit Ethernet, my question it's,
> what do i have to do, to make it faster? This time is insane! :)
>
> I know my disk does not write at Gigabit ethernet capacity, but indeed,
> lets say it writes at least at 50MBytes/sec.
>
> If we write data, at 50MBytes/sec it should take theoretically about
> 1.66 hours, its about 1h and 40 minutes or so.
>
> Of course the disk writes faster than that, at least in this case i
> have one SAS controller with 15k rpm disk's.
>
> I have in drbd.conf configured 'rate 100M'.
>
> I have drbd over the disk, and ext3 over it, but i think this is
> transparent for drbd, this should not take the drbd to slow.
>
> When it is doing the full sync, i see in '/proc/drbd' and it says it's
> copying at about 20K/sec, and since it is in bits, it is pretty slow.
>
> This is bug? Or I am the bug? :) Since I'm new to drbd, i think the
> second option will be more likely then the first one! :D
>
> Gigabit Ethernet = 125MBytes/Sec
>
> Thanks for all the help.
> ---------
> Igor Neves <igor.neves at 3gnt.net>
> 3GNTW - Tecnologias de Informação, Lda
>
> sip igor at 3gnt.net 	jid igor at jabber.3gnt.org
> icq 249075444		tlm 00351914503611
>
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