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Slow data stream on RedHat 5.8 with Netbackup


I have a problem with a slow data stream when running a Netbackup Media Server on RedHat 5.8. We are migrating systems from Solaris 10 to RedHat 5.8. The speed on Solaris 10 is about twice as fast as the RedHat 5.8 system. Also, we have no problem with earlier versions of RedHat, just 5.8. I was told that the 5.8 version is a different animal than even RedHat 5.6. Is there a different OS config I need to set up to get RedHat 5.8 and Netbackup 7.5 to get along? Possibly buffer changes, kernel tweaks, etc?



7 Replies



2: Check NIC is working as intended. Use the Netbackup GEN_DATA directive to verify path can transfer data.

Am using RH 5.8 and has no problem in trasfering >300MB/sec via 10GB ethernet


This backup is going over the

This backup is going over the SAN to LTO tape. Besides the buffers, any other tweaks?


There are special buffer for

There are special buffer for FTL configurations (NUMBER_DATA_BUFFERS_FT & SIZE_DATA_BUFFERS_FT ) . Do you got those set ?

You may also have a marginal good tape drive. Marginal good tape drives does not reach the maximal writing speed because of write corrections. Try using a cleaning tape
If the client is UNIX type check out the GEN_DATA directive (See my previous post)  in combination with a /dev/null disk stu on the media server. If this does not rock I believe you got a SAN problem then.

The "FT" buffers wouldn't

The "FT" buffers wouldn't apply in my case since I'm not using Fiber Transport, but I will double check the standard I/O buffer settings. What I'm looking for is info on the RedHat 5.8 O.S. vs Netbackup. Are there any tweaks I need to make with this config that wasn't needed in RH 5.6 or Soalris 10?




None that I am aware off. The

None that I am aware off. The only teaks we do is some TCP/IP settings. The rest is left to default

Add the following values to /etc/sysctl.conf

kernel.msgmni = 256
kernel.sem = 300 32000 32 1024
# Make sure TCP sessions are kept alive
# Recommended network settings.
net.core.rmem_max = 16777216
net.core.wmem_max = 16777216
net.core.rmem_default = 262144
net.core.wmem_default = 262144
net.ipv4.tcp_rmem = 8192 524288 16777216
net.ipv4.tcp_wmem = 8192 524288 16777216
net.core.netdev_max_backlog = 30000
Activate sysctl settings with command:  (A system reboot will automatic read and apply /etc/sysctl.conf )
sysctl –p

Sounds good, thanks.

Sounds good, thanks.


On RHEL you may have other

On RHEL you may have other services that may impact the general performance, to name two: SELinux and iptables. If these security services are active, and you have very heavy network load, as in the case of a media server, you may see noticably lower performance.

Nicolai's network settings will definately improve the TCP performance. Another part to look into is the settings of the net driver/NIC HW. You can try with/without TCP checksum offloading etc.