10-06-2009 02:05 PM - edited 03-04-2019 06:16 AM
All,
I have a SAN that replicates traffic across a 100mb MAN that I need to shape back. I created a policy that guarantees 50mb and shapes to 70mb. The mirrors broke.
We're going to contact the vendor tomorrow to see WHY it couldn't work on 50mb, but I wanted to post my policy to see if there were any changes that you would make:
interface FastEthernet0/1
description Connects to the OpteMAN DR link
ip address 172.27.1.2 255.255.255.0
load-interval 30
speed 100
full-duplex
service-policy output DR
end
class-map match-all SANTRAFFIC
match access-group name SANTRAFFIC
Extended IP access list SANTRAFFIC
10 permit ip 10.131.100.0 0.0.0.255 10.131.1.0 0.0.0.255 (16427 matches)
policy-map DR
class SANTRAFFIC
bandwidth 51200
shape peak 71680
class class-default
!
I'm not sure if I should shape or police it, but I figured that I didn't want to just drop the traffic.
Thanks,
John
Solved! Go to Solution.
10-07-2009 08:54 AM
If your SAN only sends the bulk of traffic in one direction, and there's congestion, that's where you want to apply QoS (i.e. you likely could get by with application of just one policy on one end of the link). However, assuming the SAN might want to "recover" in the reverse direction, having the QoS policy already in place guarantees service levels when that happens.
With regard to your new policy approach, I recommend you try to think of priorities between traffic more than bandwidth allocations. Bandwidth allocations are generally only necessary when the applications really need it to work (well). Otherwise, it's more a question of what traffic is serviced first when there's congestion. Assuming other traffic has users waiting, and SAN replication does not, then we want to prioritize the other traffic over the SAN replication traffic. This can be done with a policy similar to the one in my prior post. Do note, although that sample policy effectively prioritizes non-SAN traffic over SAN traffic, you might still see SAN using 95% of the link. The important point though is, although SAN uses the bandwidth it "moves aside" for non-SAN traffic.
10-06-2009 06:32 PM
I recall(?) unlike class "bandwidth" that's in Kbps, a shaper or policer uses bps. If I'm correct, you're might be shaping for 71 Kbps, not 71 Mbps.
PS:
Depending on the needs of your traffic, and the needs of the SAN mirroring, I would try the minimal bandwidth guarantee and not otherwise restrict the SAN traffic. I.e. if the bandwidth is otherwise available, why limit SAN's usage? This assumes with the minimal bandwidth defined for SAN, other traffic will push SAN aside if the bandwidth is otherwise needed.
I.e.
Something like this might work:
policy-map DR
class SANTRAFFIC
bandwidth remaining percent 1
class class-default
10-07-2009 07:01 AM
Joseph,
The reason for this is I've configured failover for all of our branches using this 100mb connection between our corporate office and the other side of the 100mb link. The SAN traffic takes up about 90mb of the pipe, but branches can usually use, and are accustomed to, 20mb. I wanted to guarantee 50mb on the link for the SAN, but I wanted to limit the amount of traffic that it could use, so I could guarantee the users at least 20mb. Maybe I should do something like:
access-list 100 deny ip 10.131.100.0 0.0.0.255 10.131.1.0 0.0.0.255
access-list 100 permit ip any any
access-list 100 deny ip 10.131.100.0 0.0.0.255 10.131.1.0 0.0.0.255
class match-any DR
match access-group 100
class match-all SAN
match access-group 101
policy-map DR
class DR
bandwidth 20480
class SAN
bandwidth remaining percent 95
And in order for this to be effective, do I have to apply at both ends of the link? From what I understand, the SAN only sends in one direction.
Thanks!
John
10-07-2009 08:54 AM
If your SAN only sends the bulk of traffic in one direction, and there's congestion, that's where you want to apply QoS (i.e. you likely could get by with application of just one policy on one end of the link). However, assuming the SAN might want to "recover" in the reverse direction, having the QoS policy already in place guarantees service levels when that happens.
With regard to your new policy approach, I recommend you try to think of priorities between traffic more than bandwidth allocations. Bandwidth allocations are generally only necessary when the applications really need it to work (well). Otherwise, it's more a question of what traffic is serviced first when there's congestion. Assuming other traffic has users waiting, and SAN replication does not, then we want to prioritize the other traffic over the SAN replication traffic. This can be done with a policy similar to the one in my prior post. Do note, although that sample policy effectively prioritizes non-SAN traffic over SAN traffic, you might still see SAN using 95% of the link. The important point though is, although SAN uses the bandwidth it "moves aside" for non-SAN traffic.
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