backup network

[X_S]

can someone explain to me how tx/rx and checksum offload configurations contribute to network performance? i did read in previous posts that tx/rx should be on and checksum offload enabled and that both server and client nics should match up. they do for majority of the clients but i'm finding out my networking group does not use flow control on the swtiches. (i'm assuming this means that tx/rx are off). One of their reasons is that it's not necessary because we have a GB network. do these settings actually improve throughput? and if so by how much?

please help, i'm going nuts here. i've done all of the performance tuning tests possible. size, number of buffers, network size buffers, etc. i'm not confident that i'm maximizing all the parts.

thanks in advance.

[Ankur_Kumar]

Hi

Here are some tips, I hope you try them out and please do inform us on the post trial performance

NIC�s
� 10Mb/sec is 1.25MB/sec (8 bits in a byte) which translates to 4.4GB/hour transfer (IEEE 802.3i)
� 100Mb/sec is 44GB/hour (IEEE 802.3u)
� 1000Mb/sec is 440GB/hour (IEEE 802.3ab which is Ether and not fibre)
� TCP/IP has overhead so the actual transfer is typically around 50-60% efficiency. If your NIC�s support it, set the checksum offload to Tx/Rx so that the NIC handles the CRC calculations instead of the CPU. This does reduce CPU overhead and improves backup speed marginally.
� Set the correct Max Transfer Unit (MTU) size � To calculate �ping server -f -l � To calculate the best Receive Window size (RWIN), calculate your MTU and then ping the server and insert the results into:
Bandwidth(KBPS) / 8 * Average Latency(MiliSec) = RWIN Size(Bytes). Round the result up so that it is exactly divisible by your Maximum Segment Size (MSS). If MTU is 1500 then MSS is 1460 (40k overhead).

Duplexing
� Half-Duplex is one way comunication, one person talks the other listens� Only one side can talk at a time
� Full-Duplex is sametime communication, if teo people are talking then they can both talk and listen at the sametime.
The debate on this issue is never ending.
You cna try out 100 Mbps with FULL DUPLEX on both the box and the switch side.
Using auto negotiate may sometimes result into network communication issues.

Chiao Come Va
Ankur Kumar

[X_S]

Thanks Ankur for your reply. i do recall finding this thread before and it definately helps. i'm sorry i should've been more clearer but i was also wondering what configurations need to be made at the switch for flow control. right now i believe they are disabled and according to our networking group, it's not necessary. do these configurations need to match up with the nics in regards to flow control and checksum (if applicable)?

[Ankur_Kumar]

Hi CP,

I guess a 100 Mbps Full Duplex on the switch side and the client will help you achieve a better yield.

chiao

Ankur Kumar