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Home > Archive > Data Storage > November 2004 > Dedicated LAN segment for backup traffic
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Dedicated LAN segment for backup traffic
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| Charles Morrall 2004-11-23, 5:48 pm |
| When discussing backup & recovery over the regular LAN, quite a few people
propose to install a dediced NIC in each server and using either a dedicated
switch or a separate VLAN in the existing ethernet switch infrastructure.
The notion of offloading backup traffic from the LAN appeals to them.
However, I'm not so sure of the idea's merits. Assuming each server is on a
gigabit LAN already, since new server hardware will most likely have it
included, I don't see much point in the hastle of creating and maintaining a
seperate segment.
In the Windows world at least, most servers won't saturate a single gigabit
link. NTFS makes sure of that. I can maybe push 30MB/s on a good day, on
average perhaps 20MB/s. In theory, a 1000Mbps should give me 80MB/s or so.
Let's say I have two dedicated backup servers, each with a gigabit link.
Even in theory, I shouldn't be able to push more than 2Gbps, thus the
backplane of the gigabit switch will not be loaded with more than 2 Gbps
inbound and 2Gbps outbound. I'm fairly sure even a mid-range gigabit switch
has a bit more bandwidth than 4Gbps. "Bogging down the network" I hear. With
what I ask? Can't the switch handle it if it's a switched infrastructure?
We've come a long way since 10Mbps hubs.
Of course, if you have a lot of traffic on the server's interface, and you
don't want to interfere with the normal production flow it might make sense.
Although I'm thinking if I load the production server with enough backup
traffic to actually congest a gigabit link, the server is probably swamped
with CPU cycles anyway.
Had the situation been that the servers are on 100Mbps, it might make sense.
But in that case, you're probably better off investing in a gigabit
infrastructure for the regular LAN, before messing with a dedicated backup
segment.
Your comments are appreciated, since these are just my own theories.
/charles
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| Faeandar 2004-11-23, 5:48 pm |
| On Tue, 23 Nov 2004 20:21:04 GMT, "Charles Morrall"
<charles.morrall@telia.com> wrote:
>When discussing backup & recovery over the regular LAN, quite a few people
>propose to install a dediced NIC in each server and using either a dedicated
>switch or a separate VLAN in the existing ethernet switch infrastructure.
>The notion of offloading backup traffic from the LAN appeals to them.
>However, I'm not so sure of the idea's merits. Assuming each server is on a
>gigabit LAN already, since new server hardware will most likely have it
>included, I don't see much point in the hastle of creating and maintaining a
>seperate segment.
>
>In the Windows world at least, most servers won't saturate a single gigabit
>link. NTFS makes sure of that. I can maybe push 30MB/s on a good day, on
>average perhaps 20MB/s. In theory, a 1000Mbps should give me 80MB/s or so.
>
>Let's say I have two dedicated backup servers, each with a gigabit link.
>Even in theory, I shouldn't be able to push more than 2Gbps, thus the
>backplane of the gigabit switch will not be loaded with more than 2 Gbps
>inbound and 2Gbps outbound. I'm fairly sure even a mid-range gigabit switch
>has a bit more bandwidth than 4Gbps. "Bogging down the network" I hear. With
>what I ask? Can't the switch handle it if it's a switched infrastructure?
>We've come a long way since 10Mbps hubs.
>
>Of course, if you have a lot of traffic on the server's interface, and you
>don't want to interfere with the normal production flow it might make sense.
>Although I'm thinking if I load the production server with enough backup
>traffic to actually congest a gigabit link, the server is probably swamped
>with CPU cycles anyway.
>
>Had the situation been that the servers are on 100Mbps, it might make sense.
>But in that case, you're probably better off investing in a gigabit
>infrastructure for the regular LAN, before messing with a dedicated backup
>segment.
>
>Your comments are appreciated, since these are just my own theories.
>
>/charles
>
I (we) have had this conversation several times and it always ends the
same way: show me the stats. In each case the stats did not show
anywhere near saturation, so no backup LAN.
Heck, the only thing we offload from the LAN for backups is NetApp,
and that goes over FC direct to tapes (switch in between). Otherwise
a boatload of clients and databases go over the LAN. No issues.
~F
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