[Box Backup] Problems with cygwin (was: Change in network usage characteristics in 0.08?)
Mon, 29 Nov 2004 10:33:35 +0000
On 28 Nov 2004, at 23:40, Per Thomsen wrote:
> On 11/27/04 9:10 AM, Ben Summers wrote:
>> There were no changes in protocol behaviour in 0.08.
>> If you use lazy mode, the daemon is designed to send a trickle of
>> backups throughout the day. So I would expect a connection to the
>> server for quite a lot of the day if the clients have extensive data
>> modifications to upload.
> Agreed. However, I'm seeing this trickle of data 24x7. No let-up. I
> know that the folks that are using the machine aren't changing files
> at 2 in the morning. They go home at 5pm, so the latest I should see
> is about 11pm or midnight for any substantial data transfer.
I agree that something is not quite right. I'm suspicious of the cygwin
>> Regarding the asymmetry over the data transfer, it does seem a little
>> odd. Obviously you're confident that the measuring system is
>> correct, so turn on ExtendedLogging and take a look at the logs and
>> see exactly what is being sent.
> I'm using MRTG, which is a robust bandwidth monitoring tool.
Yes, that's probably reliable.
>> If a directory is modified on the client, it will request a list of
>> that directory from the server until it has uploaded the files. This
>> might mean it's requested once an hour with the default settings, for
>> up to six hours. Might this be it?
>> Or if the client is a fileserver, and one of it's clients has a clock
>> which is wildly out of sync, it might be downloading the directories
>> all the time. Check the client logs for warnings about huge offsets,
>> but, say, a 12 hour offset won't provoke the warning but continual
>> filesystem write activity by that fileserver client will result in
>> more queries to the server.
>> But as usual, a look at the logs will give more clarity over what's
> I looked at the logs, and here's what I've found: The two wayward
> clients are connecting every 5 minutes and 10 seconds (+/- 3 seconds),
> rather than every hour as their config files dictate.
I can't think of any reason for that behaviour.
> Your explanation about the higher transmission rates makes sense, if
> the clients are constantly requesting the directory information from
> the server. The connection takes between 2 and 4 minutes, so there is
> always at least one client connected to the server. Hence the constant
> bandwidth drain.
> I won't have access to the client machines until tomorrow (they are at
> 2 different companies that won't be open until Monday), but I will
> look at the Windows event logs for them to see if I can glean any more
> information from them.
> My suspicion is that one of two things is happening:
> 1. There is a bug in the 0.08 cygwin client, which causes this
> behavior. My bandwidth use changed after I installed the 0.08 cygwin
> client. I installed the 0.08h win32 client on a Windows machine here,
> and observed no problems like what I'm seeing with the cygwin client.
> The cygwin client on this machine had done the 'every-5-minute' thing
> before that as well.
I have never run the cygwin client. I'm afraid I can't really help on
this. Looking at the logs may show something interesting, and perhaps
someone else who does run it can help?
> 2. The new versions of the client somehow has permission problems with
> the /var/bbackupd directory. I will be checking into that tomorrow. If
> bbackupd is unable to touch the 'last_sync_start' file, I can see how
> this can happen. last_sync_start never gets a more recent timestamp,
> and bbackupd will continually try to touch the file, and re-connect.
These timestamps are for information only. The client does not use them
for timing information. This won't be the problem.
> I'm going to be switching to the Win32 clients anyway, so this may be
> a moot point for me (if it is cygwin-related), but I wanted to make
> sure that something wasn't being missed.
I would like to know why it's doing this, in case it's a problem with
some of the non-cygwin code.