disk to disk copy through network.

[Logu_2]

Hi,
I want to make a disk copy of a root disk to a disk in another machine. Both source and destination machine have two disks each and the OS disk is not disturbed for this.

So I did this,
dd if=/dev/rdsk/srcdisk bs=1024k | ssh dstIP "dd of=/dev/rdsk/dstdsik
bs=1024k"

srcdisk is a 36GB disk and the dstdisk is a 72 GB disk. Both machines have 11.11 OS. These two machines are connected through a 10/100Mbs ethernet switch and there is no other traffic on this switch. It went on for more than 4 hours so I stopped it to check if am doing the right thing. I tried booting with the new disk and it is not completely booting, but it goes. Now my question is, will it take this much of time for copying a 36 GB. Did I miss something here. Will it boot properly If I have left it for somemore time to complete.

Thanks
-Logu

[Victor Fridyev]

Hi,

Theoretically everything is OK. Re time needed: such a copying via SCSI takes about 40 minutes for 36 GB on rp24xx computer with 440 MHz CPU. So for network it may take some hours. Try to change the bs parameter. I use bs=32768k for SCSI.
BTW, with such a procedure you loose half of the target disk. It will be seen as 36 GB disk after the copying completion.
If you want to copy your server, the best solution is make_recovery or make_tape_recovery.

HTH

[curt larson_1]

for a quick estimate of how long it will take, try transfering a 10M file.

10M x 3600 = 36G
1 sec x 3600 = 1 hour

so for each second it takes to transfer the 10M file it will take that many hours to transfer the 36G.

[Oved]

Hey,

You can also use make_net_recovery. It helps you save an image of your system to another system.

Bye,
Oved

[Bill Hassell]

Networks are VERY slow in disk terms. A very slow disk might serially transfer data at 10Mbytes/sec while fast disks run 50-100Mbytes/sec or more. In network terms (which is always bits), that's about 80 to 800Mbits/sec without overhead (IP headers, packet segmentation, retries, speed of the sending and receiving machines, even patch levels). It's very difficult to maintain anything close to the network's maximum bandwidth, so figure about 50Mbits/sec for a 100Mbit LAN. That's 5 Mbytes/sec, 300Mbytes/min, 18Gbytes/hour. So best case, it might take 2 hours but that is ideal. 4 hours might be more reasonable.

However, all this assumes that the two LANs are running at 100Mbit/sec in full duplex mode. Verify this with lanadmin on both ends. A simple ftp of a 100Mbyte file will also verify the link speed fairly quickly.

Copying a root disk to another machine is alwqays problematic. This will only work *IF* the two machines are identical. I/O channels must be identical, LAN cards must be identical, and of course, the machines must be the same model. Any variations and boot problems will be normal. Get a copy of Ignite/UX which is designed to accomplish exactly this task over the network (a lot faster too).

[Hein van den Heuvel]

Ditto Bill's reply. It is all to easy to have a 'weak link' in a network chain.
Make sure both system interafces are configured 100mb and full duplex. And even then count on 2+ hours as per 'back of the enveloppe' calculation. 'Calibrating' / checking with a know 100Mb file is a worhwhile step also.
Finally, for larger transfers I always pipe into a compress tool, over the net, and uncompress.

Hein.