how to speed up the backup

[a2z]

Hi,
I am completely new to legato netwerkor world. We are trying to backup a 50 GB database using RMAN/Legato Networker and it is taking 5 hours !!! I am not sure where to look to tune it. We have multiple channels in RMAN to backup and using DLT7000 drives and 100 MB/sec ethernet connection.

 

[TDun]

Make sure your network card is not set to auto-negotiate, but is set to full-duplex 100Mbit.
A DLT drive can handle 5-10Mb/s, so can handle 18-36G/hr if it is kept streaming.
What is your DLT connected to? An ultra-wide scsi controller? If so, then that is not the bottleneck.
How much free capacity is their on your lan, that the backup data can use, is that a bottleneck?

 

[fraxx]

Just wondering, what performance are you expecting?
The native speed of a DLT7000 is about 17GB/hour. Just by going by this number the backup should be completed in a little less than 3 hours.
A lot of factors here. 100Mbps (which I assume you mean, not 100MByte/s) goes to about 8 MByte/s useful data when you've taken out all the Ethernet & TCP/IP overhead.
Then it's database. Are you backing it up online or as a file dump?
The OS? Backup server hardware? Anything else on the SCSI bus to the DLT7000? Are you using a loader?
We need a lot more info to see where the bottleneck is.
/charles

 

[jgarmer]

Make sure compression is turn on at the tape drive as well. You get higher bit rates.

joe

 

[fraxx]

I'm not sure compression is always such a good idea. In this case, the network can give you about 8 MB/s of useful data. A rule of thumb I've learned is to be sure to have a data stream of three times the native speed of the drive. In this case that's 3x5=15MB/s, about double the network speed. If the data stream falls well bellow this, the tape drive's buffer gets underrun and the tape drive stops. DLT7000 doesn't slow down, it stops. It has to wait until the buffer is filled, the tape has to be rewound and repostioned on the last CRC check mark, and the backup starts again. If the data stream is consistently too low, the above process is repeated again and again. This is commonly know as "shoe-shining" and will positively kill performance, and also put excessive wear and tear on tapes and drives.
Therefore, experiement with turning compression off and on, establish some benchmarks in your enviornment and see what works best for you.
/charles

 

[jgarmer]

Okay use compression and go get a couple gig nics that will get you going. Gig nic are much cheaper now. Foot balling shoe shinning. We all get a kick out of DLT technology.

joe

 

[pmwut5]

What version of Legato are you running ? To verify the network setting between the Legato Client and Server try and ftp a large file (20MB) from the client to server. On a 100Mb connection you should approach 10MB/s. If it is much slower then reasearch network cards and port setting.

Once the network is verified then we are in the Legato domain. Is the 50GB volume one single volume - if so Legato will only start one savestream to backup the data irrespective of whether the volume is on multiple physical drives.

What is the spec of the client -- I have noticed a direct correlation between CPU speed and backup performance.

Our Pentium III 900Mhz backup at around 7MB/s sustained peaking at around 10-13MB/s. Pentium III 400 are only around 5MB/s but this does depend on the type of data.

Hope the above helps

 

[a2z]

Thanks a lot to everyone involved in discussion. It was quite a learning experience. Let me just give you a little bit more detailed information about architecture we are using.

We have HP-UX OS. We have around 30 clients defined in Legato Networker on the backup server which in turn is connected to storagetek jukebox which has 10 DLT7000 tape drives. There are 9 ultra-wide SCSI controller connections to 10 tape drives and one robotic arm. There are 2 100 Mbps cards dedicated just for backup. Seems network connection is the bottleneck. Since i tried to do ftp from client to backup server and it is all the time less than 5 MByets/s.
I would like to list all the information you asked for

1. We are using full-duplex 100 Mbit network cards
2. I can see that there are spikes tape write speed to 5 MB/s and then drops down to 400KB/s and jumps to 1200KB/s. And if database backup is going on more than one tape then write speed is reduced by that factor. Does that mean tapes are not streaming ? Might be due to insufficient incoming stream speed.
3.We did not turn off compression, i guess in our case it might be helping since network speed is not much. Should we try turning it off?
4.We would like to get Gig nic, do we need to make sure any other settings once we install Gig nic like processor speed.
5.Backup server is L2000 model with HP-US OS and it is 3 CPU machine. I will have to dig in further to get processor speed.

For now what i have understood that we need upgrade on both client and backup server network cards. Once again i really appreciate all your help and please let me know if we need to take any other steps.

 

[pmwut5]

The L2000 is a very fast machine and is very cable of driving all nine DLT drives flat out. Are the 2x 100Mb card aggregated into a 200Mb pipe ?
I would say it is the client end that needs investigation.

DO you have any unix clients - I.E. similar in spec to the server to test performance.

I have an N-4000 server with 2 gigabit back network and I still get NT clients with gigabit cards in that can only transfer 5MB/sec. As I said before NT and Novell backup performance improves with CPU speed.

 

[TDun]

Check the client ends are also set 100Mbit Full duplex with nothing as auto.
Then try with the ftp again and see if it improves.

 

[jkalbus]

The next suggestion on the network side would be to add another network just for backup purposes.

As you state you have 2 NICs on your HP Box - how about using one for backup, and one for public lan? You need to assign two IPs to the two NICs and two DNS Names to the two IPs - then tell the client to use the Backup Name for the backup server and everything will go better.

example:
/etc/hosts

192.168.0.1 L2000
192.168.1.1 L2000-bkp

client entry in networker:
server network interface entry: L2000-bkp