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consequent backups much slower - why?

Proposed Answer consequent backups much slower - why?

  • Friday, July 20, 2012 7:44 AM
     
     
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    Hi all,

    I run virtual Windows Server 2008 R2 in VMware ESXi 5.0 from local datastore (8 SAS disks in raid 60) on HP ProLiant DL380 G7 server. When i create virtual disk on the same datastore, attach it to virtual Windows Server 2008 R2 and use it as dedicated backup volume i get great speeds for first full backup, and also every consequent backup. This way full exchange backup of around 500Gb gets backed up in less than 2 hours, which I am very satisfied with. However, my fast local datastore is getting low on space and i wanted to offload backups to cheaper external storage. I took older HP ProLiant ML350 G5 with 6 SATA disks in raid 10 and exported them to ESXi (in first test over NFS, in the second over iSCSI, I'll explain right away) from FreeBSD 9.0.

    Now, when i create virtual disk on NFS/iSCSI datastore and attach it to Windows Server 2008 R2 as dedicated backup volume, i noticed that first backup gets done with satisfactory speed for this kind of hardware (around 10Mb/s), and this backs up my domain controller of around 20Gb in 30 minutes. But every consequent backup takes much longer, up to 4 hours for the same amount of data, and disk activity shows no more than 1Mb/s for reads and writes.

    I do not think it is disk/controller/network I/O problem, because if i start to copy one file from ESXi host to the same datastore, and the other file from the same datastore to the ESXi host while backup is running, files get copied fast and i see increase in disk read/write activity.

    So, could this problem be related to some windows backup specifics? And if so, could i get an advice how to get better speeds for consequent VSS backups of Windows virtual servers to NFS/iSCSI datastores?

    Thank you in advance.

     

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  • Tuesday, August 07, 2012 9:22 PM
     
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    Hello ux666.

    Look at this link, it will explain how VSS works and maybe you can find a solution:

    http://technet.microsoft.com/en-us/library/ee923636(v=ws.10).aspx

    You can monitor Windows host using Performance Monitor (Avg Disk Queue Lenght) and your bandwith with iperf. What backup solution youre using? If you can put more information about your trouble trip, please, help me to help you.

    Thanks.

    Luiz Eduardo MCP Windows Server 2003. MCTS Network Windows Server 2008. MCTS Application Windows Server 2008. MCTS SQL Server 2008. Se a resposta ajudou, colabore com o Fórum e classifique.

     
  • Thursday, August 09, 2012 5:03 AM
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    Any updates for your issue?
     
  • Friday, August 31, 2012 3:58 PM
     
     
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    Any updates for your issue?
    I hope it is resolved.

    Luiz Eduardo MCP Windows Server 2003. MCTS Network Windows Server 2008. MCTS Application Windows Server 2008. MCTS SQL Server 2008. http://sqldicas.com.br - Se a resposta ajudou, colabore com o Fórum e classifique.

     
  • Friday, October 19, 2012 2:06 PM
     
     
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    After some time I am here again. Delay is partly due to testing and partly to summer vacation.

    I moved my tests to ProLiant ML350g5. It runs FreeBSD 9.0 x64 with 8Gb of RAM. I have 6x500Gb sata disks in raid 1+0 on integrated SmartArray E200i RAID controller. Cache is enabled for both controller and disks, as instructed here, but unlike there i have set write to read cache ratio to 100/0 (as opposed to 0/100 as described). Storage is presented to ESXi over NFS as a datastore where virtual Windows Server 2008 R2 has its system disk (around 20Gb) and backup volume of 40Gb. Backup is done with integrated Windows Server Backup (full backup to a dedicated volume).

    As I said, first backup goes well (20Gb in 20min), second one much worse (20Gb in 6hrs).

    What exact information could I provide so you can help me?

    Thank you in advance.

     
  • Monday, October 22, 2012 11:35 AM
     
     
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    Hello ux666.

    What are you means when you says "first backup"? It is the first backup of the day? It is manualy started? The subsequent backups are full and started exactaly like first backup? Did you read the VSS link that i sent to you?

    Your environment is not really simple, i sugest you to monitor while your backup is running. Can you post more details about your backup methods? 

    Regards.

    Luiz Mercante
    MCITP SQL 2008 | MCTS SQL 2008 | MCTS Windows Apps | MCTS Windows Network | MCP 2003
    sqldicas@outlook.com
    http://sqldicas.com.br

     
  • Tuesday, October 23, 2012 8:01 AM
     
     
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    Hi Luiz,

    "First backup" means a backup when there are no previous backups on dedicated backup drive. Backups are not started manually. They are configured as scheduled backups. You are right when you say that subsequent backups are full and started exactly like first backup. I have read the VSS link you have sent me, and it did not solve my problem but I got better understanding of VSS.

    I switched NFS server from FreeBSD to CentOS to check if this could be FreeBSD-related issue and it turned out that CentOS does not have the problem of slower consequent backups. While monitoring disk reads and writes on NFS server, i noticed that first backup only writes to disk, while consequent backups do much more reading than writing. This is probably due to the way VSS works - consequent backup is checking the previous backup (a lot of disk reading) and writes only the differences (occasional disk write).

     
  • Wednesday, October 24, 2012 6:00 PM
     
     
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    If you are making a full backup or a dif/inc, you just need to read the source records that have the archive bit ON or OFF. I cant understand why are you having a lot of reads after your first backup. Please, answer just few more question, maybe i can help you a little more.

    1- What backup software are you using?
    2- You are shutting down your VMs, connecting that volumes in your backup server and then making your backups? Can you describe it better?

    Thanks

    Luiz Mercante
    MCITP SQL 2008 | MCTS SQL 2008 | MCTS Windows Apps | MCTS Windows Network | MCP 2003
    sqldicas@outlook.com
    http://sqldicas.com.br

     
  • Thursday, May 02, 2013 11:16 PM
     
     
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    Hello ux666.

    Look at this link, it will explain how VSS works and maybe you can find a solution:

    http://technet.microsoft.com/en-us/library/ee923636(v=ws.10).aspx

    You can monitor Windows host using Performance Monitor (Avg Disk Queue Lenght) and your bandwith with iperf. What backup solution youre using? If you can put more information about your trouble trip, please, help me to help you.

    Thanks.

    Luiz Eduardo MCP Windows Server 2003. MCTS Network Windows Server 2008. MCTS Application Windows Server 2008. MCTS SQL Server 2008. Se a resposta ajudou, colabore com o Fórum e classifique.

    Can we finish this thread?

    Luiz Mercante
    MCITP SQL 2008 | MCTS SQL 2008 | MCTS Windows Apps | MCTS Windows Network | MCP 2003
    sqldicas@outlook.com
    http://sqldicas.com.br


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