Hello,
VSS:
The original Bacula VSS code was written by the developer by using
global values (this is not a critique because it seemed logical at the
time), which means that if two threads try to use the Bacula VSS code at
the same time, they will corrupt data. Consequently the Bacula Windows
FD explicitly forces only one VSS job to run at a time. This can be
fixed and I think Bacula Systems has experimental code that does it, but
for the moment it is not on our priority list, though as Windows
filesystems get bigger and bigger, it is becoming more important. We do
have some users that must run multiple simultaneous jobs and they do so
by turning VSS off. I hope that one day, in the next year or two,
Bacula will not only handle multiple simultaneous VSS jobs, but that it
can automatically use multiple threads in the same job, which would, in
most cases, avoid the need for running two or more jobs.
Performance:
By the way, my experience is that Windows is simply slower than Linux
when doing filesystem operations, thus it is very hard to have Windows
FDs that get the same performance that we see on Linux. I have never
investigated the exact reasons, but some that I suspect are: the Windows
file related APIs are far more complex than Linux, sometimes requiring
far more API calls to get the same info that Linux gives in one call;
Windows networking seems to be particularly slow -- this may be due to
poor out of the box tuning or simply that Windows programmers have never
paid as much attention to networking performance enhancements as the
open source Linux community has.
Best regards,
Kern
On 12/05/2014 10:24 PM, Patrick wrote:
> Hi Andreas,
> Hi Josh,
>
> Thanks for your hints toward NTFS performance. I have checked the access time
> setting on the windows file server and on all it was disabled. The Windows
> Server 2008 R2 are configured with the Fileserver role, I think Windows set
> the value automatically.
>
> During my research from the NTFS side I stumble over VSS again and I observed
> that even I configured the Maximum Concurrent Jobs on the Windows FD Client
> to 10 only one job backups real data, the others just wait before the VSS
> line in the log file. After the first job finished, one of the other print
> the VSS line and backup real data. It seems that only one VSS shadow copy can
> be use by the bacula-fd.exe.
>
> I couldn’t found anything in the documentation [1] and only this on the
> mailinglist, without a concrete answer [2].
>
> Can I configure the bacula-fd.exe two use more than one VSS shadow copy at
> the same time?
>
> I talked to our windows expert and he told me that Windows Server 2008 R2 can
> have up to 64 concurrent VSS shadow copy.
>
> Thanks again,
> Patrick
>
> [1]
> http://www.bacula.org/5.2.x-manuals/en/main/main/Windows_Version_Bacula.html#SECTION003480000000000000000
> [2]
> http://adsm.org/PRIVOXY-FORCE/lists/html/Bacula-users/2012-09/msg00151.html
>
>> On 01 Dec 2014, at 18:06, lst_hoe02 AT kwsoft DOT de wrote:
>>
>>
>> Zitat von Josh Fisher <jfisher AT pvct DOT com>:
>>
>>> On 11/29/2014 5:43 AM, Patrick wrote:
>>>
>>>> Hi Josh, Thanks for your reply.
>>>>> You can try to isolate the problem. Try running a Windows backup with
>>>>> VSS, compression, and encryption all turned off. Compare a Windows VM
>>>>> against a Linux VM on the same host if possible.
>>>> I don’t use compression or encryption, but VSS. I disabled VSS and get
>>>> about 40 MByte/s. If I also set acl support = no, I get about 43
>>>> MByte/s. It’s better, but far away from the 90 MByte/s from a linux box
>>>> with similar data. Last night I have took a look at the bacula console
>>>> during the full backups and could see one Windows clients with 65
>>>> MByte/s. This server hosts a SQL Server with big database dump files.
>>>> The Bacula File Daemon is faster with big files. How can I tune the
>>>> Bacula File Daemon to increase the transfer rate for a lot of small
>>>> files? Can I set the maximum memory usage? Is a ramdisk which collects
>>>> the files from the hard drive and send it as bunches to bacula possible?
>>> You can change the MaximumNetworkBufferSize to 32k in both the client
>>> and SD configurations. Slowdowns of Windows clients have been noted
>>> before for 64k+ buffer sizes.
>>>
>>> You might also consider tweaking the NTFS filesystem on the Windows
>>> client. The filesystem parameters are in
>>> HKLM/system/CurrentControlSet/Control/FileSystem. Setting the DWORD
>>> value NtfsDisableLastAccessUpdate to nonzero will prevent a write to
>>> the disk each time a file is accessed. It is equivalent to the noatime
>>> option of ext4, so can definitely impact jobs like bacula-fd that are
>>> reading lots of files.
>>>
>> Technical details in case of NTFS can be found here for example:
>> http://technet.microsoft.com/de-de/library/bb457112%28en-us%29.aspx
>>
>> Regards
>>
>> Andreas
>>
>>
>>
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