You will be limited on writes to the speed of your drbd replication link
(If using protocol C, which you should if you care about your data).
Network teaming, bonding, etc will not work because you are pretty much
going from a single IP to a single IP, so there is no benefit in
aggregating NICs. If you really want to use the full potential of your
backend storage, you need to purchase 10GBit network cards for drbd.
A very long time ago I ran some benchmarks:
https://services.ibb.gatech.edu/wiki/index.php/Benchmarks:Storage#Benchmark_Results_3
If you look at the first result in the table, even if the backend is
faster (I got over 200MB/s writes on a non-drbd partition), the drbd
partition maxes out for writes at around gigabit speed 123,738KB/s.
I currently have a new set of servers with the ARECA SAS controllers and
24 1TB drives. The backend can write up to ~500MB/s but when I use drbd,
the bottleneck is just 120MB/s.
I guess the only other configuration that may help speed would be to
have a separate NIC per drbd device if you backend is capable of reading
and writing from different locations on disk and feeding several gigabit
replication links. I think it should be able with SAS drives.
e.g
/dev/drbd0 uses eth1 for replication
/dev/drbd1 uses eth2 for replication
/dev/drbd2 uses eth3 for replication
... you get the idea...
HTH,
Diego
Chris wrote:
Hello everyone,
I have a raid 6 setup with lvm and my write is fast around 500mb sec. I
want to but the drbd on top the lvm and the another lvm on top of drbd.
I'm wondering
1. Will why write speed decrease because drdb needs to write the data to
the secound server?
2. My raid 6 is 1tb is it better to break it up into 4 250gig or two
five hundred gig and 4 drbd for better speed?
All the data that is going thru drbd is connected by 1gig cross over
cable to both servers. Just thinking that the gig link may slow down
brbd with drive size and speed of drive. Sas 15k
This setup is for two xen server that will be using the allocated lvm
chunck
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Diego Julian Remolina
System Administrator - Systems Support Specialist IV
School of Physics
Georgia Institute of Technology
Phone: (404) 385-3499
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