frecover across the network

[John Walker_1]

I am performing an frecover task from one machine to another for reasons of DDS compatability. Can anyone please tell me why this takes so long? It takes upwards of 6 hours to even find the relevant files let alone recover them. Both machines are on the same LAN. Is there an explanation for the time taken, and is there any way of speeding this up at all?

[Bill Hassell]

There is a lot of missing information. Is the LAN 10BaseT or 100BaseT or soemthing else like TokenRing? If it is 100BaseT, what does lanadmin report when you display the first page of data concerning the speed and duplex? If it reports 100BaseT half-duplex, that is your problem and ALL LAN transfers over that link are running much slower than 10 Mbits. Turn off autonegotiation on both ends.

Now 6hrs would be quite good for a DDS3 tape that has about 20 Gb of compressed data. It's hard to say if the transfer rate is slow until the amount of data and the link speed is stated.

There's nothing you can do to frecover...it is running as fast as it can.

[John Walker_1]

I have checked lanadmin:
Type (value) = ethernet-csmacd(6)
MTU Size = 1500
Speed = 10000000

But why does it take so long to find the files on tape before it even performs the recovery of the data? This is what is taking in excess of 6 hours+

[James R. Ferguson]

Hi John:

Have you tested how long an 'frecover' would take without involving the network?

If you are using the default options in the 'config' file when you create the tape in the first place then you are sacrificing efficiency.

Build /var/adm/fbackupfiles/config to look something like this:

blocksperrecord 128
records 32
checkpointfreq 256
readerprocesses 2
maxretries 5
retrylimit 50000000
maxvoluses 100
filesperfsm 200

Regards!

...JRF...

[John Walker_1]

Thanks James, but the config settings do not enter the equation. The story is this..the tape was created by one of our servers on a DDS2 drive. The machine I am trying to restore the data to only has DDS1 drives, so I can only recover the data by putting the tape in another machine with a DDS2 drive and frecovering across the network. I appreciate that the data recovery will be a lot slower than if the tape was in the machines' own drive
but why does it take so long to read the tape until it finds the required files. I have it running now and it has been going for over 3 hours already and still hasnt found any of the files yet. And yes I know they are on the tape as I have recovered them before.

[James R. Ferguson]

Hi (again) John:

The 'config' file parameters used when the 'fbackup' tape was created are stored in the tape's volume header and *are* used by 'frecover'.

Document #PU9408251055 notes:

/begin_quote/

The filesperfsm parameter controls the number of files between each fast search mark and has an impact on the time to recover files from a
backup tape. During a recovery, the tape streams rapidly to the nearest fast search mark then slows down to check each file, up to the required one.

Setting filesperfsm to a low value means that there will be fewer files between each fast search mark. With older DDS drives this could
result in much faster recovery of individual files. With the newer DDS drives, such as the compression drives, recovery operations are much faster than before and reducing the value of this parameter is usually not necessary.

/end_quote/

...JRF...

[John Walker_1]

Thanks for the information. It is useful to know, but sadly the config cannot be amended for this particular tape. I guess I will just have to sit and wait - or upgrade the drive on my machine!!

[Paula J Frazer-Campbell]

John

What vervions of NFS are running on these machines? as connecting a version 2 machine to a version 3 machine and vica versa has speed problems.

Just and idea

Paula

[Bill Thorsteinson]

AYou may find it faster to run the recover on the system that has the drive. This will eliminate the network from
your tape access.

If you have the space you could recover to the system
with the drive and transfer the files afterwards.

If not NFS mount the drive on the remote system and
recover to the NFS mount point.

I find recovers run much faster on the server with
the backup set (on disk or tape).