Arcserve backup gradually slowing down

dekkar
dekkar used Ask the Experts™
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Hello, I have an Arcserve backup job that runs every night. The job takes around 11hrs to backup 640Gb of data.


The backup starts at around 4,000Mb/min, and as time goes on it gradually slows down to around 500Mb/min.

I have tried this on both our SCSI LTO drive, and USB3 RDX drive, and they both behave the same way.

The biggest file in the backup is 420Gb, and this is where the major slowdown happens.

It seems that the job speeds up again once it completes every "subjob" (Exchange, SQL etc etc)

So every subjob will start at around 4,000Mb/min, and gradually slow down. So the bigger the files it has to backup, the slower it will get.

This will happen no matter where the data is, over the network or on a local disk...


I dont think its the network, as while this backup is running, I can copy data to the local server at over 6,000Mb/min......  and bakup to disk jobs in Arcserve run fine. It seems its only backup to tape jobs.

I also question if its the hardware, as both USB and SCSI devices behave the same way.

Any help would be appreciated.
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Aaron TomoskyDirector of Solutions Consulting

Commented:
Usually this is because it can only write at the slower speed. At the beginning it uses ram as a cache and is only limited by the read speed. But as ram fills up, it slows down to eventually be the speed of the write location.
First -- you use "Mb" when listing your speeds.   By convention, "Mb" is "megabits", and "MB" is megabytes -- that is, it takes 8 Mb to make 1MB.   Do you really mean to be talking about megabits?  The difference is less than an order of magnitude, but still rather significant.

Second -- Which LTO drive and tapes are you using?  There's more than an order of magnitude performance difference between LTO-1 and LTO-5.  

I don't believe that this is a target speed problem (that is, a problem with the thing you are writing to).  Your test that showed the same behaviour to both tape and RDX seems to eliminate that.  Nor does it sound like a network problem.

Rather, there's something about your server or disk configuration that is not optimal.  If you're running Windows of some flavor, check PerfMon to see if there is something degrading over time.   Perhaps your version of ARCserve has a memory leak and its performance is degrading over time.  Maybe your disk subsystem is performing poorly -- what are your topology and underlying hardware?  Which RAID controller are you using?

I would certainly check to see if there is a newer version or update to ARCserve in any case.
Aaron TomoskyDirector of Solutions Consulting

Commented:
" and bakup to disk jobs in Arcserve run fine. It seems its only backup to tape jobs."
It's the speed it can write to the tape. Lots of factors involved, compression actually can speed up the process.
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Author

Commented:
Hi,... sorry... Everything is in MB.... The tape is an LTO4......

I'm thinking of rebuilding the server....... I just have spent over 6 months trying to fix this, and maybe there is something else running on the server that is causing the problem....

I'll rebuild it with just Arcserve running, and see if that makes things run faster.
Aaron TomoskyDirector of Solutions Consulting

Commented:
Run resource monitor. Should get right to the issue pretty quickly

Author

Commented:
Ok, willl give it a go now.

Thanks,

Author

Commented:
Hmmm the backup has been running for 45 mins... Backed up 105Gb...

Started at 3900MB/sec, and is now at 2480MB/sec and dropping..... the free memory has remained at around 4GB.....
Aaron TomoskyDirector of Solutions Consulting

Commented:
How much is the backup process using? You can also see the io on the other tab with separate reads and writes. Watch if the reads are more than the writes.

Author

Commented:
There are a few processes active:

Tapeeng.exe 15MB
CARunJob.exe 20MB
CAagstart.exe 42MB


the CA stuff isnt using that much... the biggest resource is w3wp.exe with 915MB... and SQL with 769
If you are still looking for Answer the visit

Best location to get answer would be https://communities.ca.com/

or you can go to ARCserve Chat (Free)

http://www.arcserve.com/us/support.aspx
Commented:
Hi.... I ended up fixing it by buying a new piece of hardware......

I did try replacing the motherboard in my current server, but it didn't make a difference. I have no idea what was causing the slowdown. I reckon something in the OS/software..... I don't think it was hardware related, as I pretty much tested every piece of hardware in the server.

Author

Commented:
There was no answer so I replaced the server.

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