EMC Data Domain 与 Oracle RMAN的备份速度问题

Question

各位BRS专家，有一个Data Domain备份速度的问题希望得到帮助。原文如下： The server is an IBM AIX 6.1 P7 frame running with VIO front end. The current production backup is done using a VTL with an 8Gb fiber connection and the server is a media master. The datadomain connection is also thru the VIO and uses a 10Gb fiber. The database is approximately ~1Tb in size. When a RMAN full backup is done to the VTL the backup will complete in about 35 to 40 minutes. However, when a backup is done of the same database is done to the datadomain device the length jumps to 1 hours / 20 minutes. Also, there is another database which is 283Gb in size and it also takes about 1 hour / 10 minutes to backup to the datadomain - the confusion is why would a backup of 283Gb and 1Tb be so similar. In addition, a couple of times it has been found that  a backup to the datadomain really slows down and a unmout/remout of the device needs to be done to return the backup to at least a consistent speed. While I was writing this discussion a backup was running to the datadomain of the 1Tb database at the same time I was running a iostat –VF /datadomain/OracleMMA 30 1000 command – suddenly there was a significant drop off in speed as seen below: FS Name: % tm_act Kbps tps Kb_read Kb_wrtn /datadomain/OracleMM - 70327.4 68.7 0 2109440 FS Name: % tm_act Kbps tps Kb_read Kb_wrtn /datadomain/OracleMM - 17331.6 17.0 0 519992 From that point on the device has not regained the speed – earlier I was seeing speeds like 2.9 to 3.0GB every 30 seconds. I have no idea what would cause such a drop – it should be noted this backup is the only one being written to the datadomain at this time. We have separated the Oracle data files and the archive logs into separate directories. The RMAN command is setting the FILESPERSET=1 and encryption/compression are not set. What I’m trying to figure out is have we configured the device incorrectly or are their some methods to see if we can account for the differences in the throughput. In addition we have separated the Oracle data files and the archive logs into separate directories. The mount options are as follows: DD01 /data/col1/DBlogs /datadomain/DBlogs nfs3 Dec 14 11:09 cio,rw,bg,hard,nointr,rsize=32768,wsize=32768,proto=tcp,vers=3,timeo=600 DD01 /data/col1/OracleMMA /datadomain/OracleMMA nfs3 Dec 14 11:09 cio,rw,bg,hard,nointr,rsize=32768,wsize=32768,proto=tcp,ver s=3,timeo=600

herohj · Answer

Hi ,

You talked about VTL and NFS for your backup method ,so I am not quite sure what is exactly the backup method you are in use .

There are tons of the factors could contrbute to the slowness of backup ,so without exact description we hardly pin point the root cause .

zhaos2 · Answer

谢谢答复！上述描述其实比较了VTL及DataDomain两种备份方式，同样对1TB数据库进行备份，用DD方式（1h20m）明显慢于VTL （35m - 40m）。另外用DD备份283GB的数据库也用了1h10m。想请教一下是否配置有什么问题。如果需要了解具体环境，请列出相应的问题。

herohj · Answer

VTL is part of data domain ,data domain is a name of our product ,so I am not sure what you are referring for VTL and DD?

we have CIFS/NFS/VTL and dd boost inside data domain which could be in use for production backup .Currently dd boost and vtl go through over fibre channel .You need take a look at the host side and networking side to narrow down what's going on .

For networking side ,you can take a TCP/DUMP then analyse if there is frame dropped /timeout like that ...

Inside host ,you should check the configure of NIC configuration .

zhaos2 · Answer

Thanks Jim! Obviously the VTL in this case is a product from other vendor, and Data Domain currently can only support NAS with Oracle RMAN, so NFS with AIX in this case.

herohj · Answer

You are not correct and I am not clear from what you say.If you are talking about RMAN backs up to DD directly ,that is for DDBOOST technology not NFS.

Assuming you are correct ,for NFS technology backing up to DD by backup application ,there are lots of factors can impact the performance .

1.You should check the real LAN speed between AIX and DD,iperf tool can get the speed if you not sure .

2.depends on what is the tcp/ip window size on NIC in AIX

3.did you enable the jumbo frame from switch and whether you set the MTU from both DD and AIX to 9000

4.AIX may disable the selctive ack feature by dedault ,should get it enabled but that should investigate tcp/dump

again ,there are quite lot of things impact performance ,please open a ticket to DD that our support engineer will address it for you !

liulei_it · Answer

hi ,buddy. the block read by Oracle RMAN, it is logical not physical .So, when the backup begin, Oracle RMAN just scan all Oracle form block and backup them  no matter whether they are same size. Is it test without acutally woking?  You can set 'alter database enable block change tracking' in your Oracle when executing increase backup,then you can find out it is shorter than before.

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