[DRBD-user] DRBD - Slow Performance

Dan Lavu Dan.Lavu at rivermine.com
Mon Feb 15 23:37:10 CET 2010

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


I posted most everything on the initial email, but to recap, I'm pretty
sure it's a disk issue. 

When copying a large file to the raid, using SFTP I see IO read and
write times of 30-35MB/s and I see transfer rates of 20MB/s. Keep in
mind I'm syncing between two datacenters, Texas to Illinois. 

When it's syncing, iostat shows read write times of 2MB/s. I even
created a ramdisk for an external metadisk and I saw no improvement. 

If my raid can easily write at 30MB/s why is the DRBD sync capped at
2MB/s? This is a RAID 5, with two logical volumes. 


Dan Lavu 

-----Original Message-----
From: Digimer [mailto:linux at alteeve.com] 
Sent: Monday, February 15, 2010 5:30 PM
To: Dan Lavu
Cc: drbd-user at lists.linbit.com
Subject: Re: [DRBD-user] DRBD - Slow Performance

Dan Lavu wrote:
> Digi,
> Thanks for advance again, but I've already tried this. I'm still
> at 2MB/s. I've exhausted IRC any google searches involving DRBD slow
> sync. I'm really contemplating rebuilding the machine with a RAID 10
> enhance performance but I still do not know if this is going to
> the issue, any thoughts about this? Thanks in advance.
> Best Regards,
> Dan Lavu

How is performance on the local disk? Have you checked using something 
like: fdisk -tT /dev/sda? Also, what performance do you get if you write

a large file to the array?

What I am wondering is; Is the performance limitation a DRBD issue, a 
disk issue or a sync'er issue. What kind of performance do you get 
sending a file over the DRBD's network interfaces directly (not writing 
to the DRBD disk)?


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