Re: VMware Training
[See below] On Feb 19, 2014, at 10:46 PM, Jay Ashworth j...@baylink.com wrote: Why bother with a clustering FS, then, if you cannot actually /use it/ as one? - jra On February 19, 2014 10:44:22 PM EST, Jimmy Hess mysi...@gmail.com wrote: On Wed, Feb 19, 2014 at 2:06 PM, Jay Ashworth j...@baylink.com wrote: - Original Message - From: Eugeniu Patrascu eu...@imacandi.net [snip] My understanding of cluster-aware filesystem was can be mounted at the physical block level by multiple operating system instances with complete safety. That seems to conflict with what you suggest, Eugeniu; am I missing something (as I often do)? When one of the hosts has a virtual disk file open for write access on a VMFS cluster-aware filesystem,it is locked to that particular host, and a process on a different host is denied the ability write to the file, or even open the file for read access. Ghods how I miss real tightly coupled clustering, shared hierarchical storage and true clustered filesystems like in VMS. Here’s a 35 year old OS that still is better than anything we have today. Secure, granular prigs, file versioning, multiple simultaneous cluster interconnect physical layers, POSIX compliance, heavy distributed networking and strong system services built in. When people tell me about clustering today and then add these caveats about how clustered files aren’t actually sharable or that you can’t have complete orthogonality. I guess I’m now old. -d - Dan Shoop sh...@iwiring.net 1-646-402-5293 (GoogleVoice)
Re: VMware Training
On Feb 20, 2014, at 1:48 PM, Jimmy Hess mysi...@gmail.com wrote: The locking restrictions are for your own protection. If the filesystem inside your virtual disks is not a clustered filesystem; two instances of a VM simultaneously mounting the same NTFS volume and writing some things, is an absolute disaster. Under normal circumstances, two applications should never be writing to the same file. This is true on clustered filesystems. This is true when running multiple applications on a single computer. Why should two applications should never be writing to the same file? In a real clustered *file*system this is exactly what you want. The same logical volume mounted across host cluster members, perhaps geodistantly located, each having access at the record level to the data. This permits HA and for the application to be distributed across cluster nodes. If a host node is lost then the application stays running. If the physical volume is unavailable then logically shadowing the volume across node members or storage controllers / SANs permits fault tolerance. You don’t need to “fail disks over” (really logical volumes) as they are resilient from the start, they just don’t fail. When the shadow members return they replay journals or resilver if the journals are lost. I’d note that this can be accomplished just so long as you have a common disk format across the OS nodes. These problems were all resolved 40 years ago in mainframe and supermini systems. They’re not new. VMware has been slowly reinventing — more accurately rediscovering — well known HA techniques as it’s trying to mature. And it still has a lot of catching up to do. It’s the same tale that microcomputers have been doing for decades as they’ve come into use as servers. However I’m not sure what all of this has to do with network operations. ;) -d - Dan Shoop sh...@iwiring.net 1-646-402-5293 (GoogleVoice)
Re: NTP DRDos Blog post
On Feb 20, 2014, at 11:43 AM, Jon Lewis jle...@lewis.org wrote: On Thu, 20 Feb 2014, Brian Rak wrote: That's not a new term. http://en.wikipedia.org/wiki/DRDOS DRDoS, a type of network attack named Distributed Reflection Denial of Service. http://en.wikipedia.org/wiki/Distributed_Reflection_Denial_of_Service#Reflected_.2F_Spoofed_attack Or Digital Research Disk Operating System...if you're old enough. Who knew DRDOS would become popular [again]? I had wondered what the problem was, older than age, with anyone trying to run DRDOS. It should fit in the memory and cpu footprint of a modern toaster. -d - Dan Shoop sh...@iwiring.net 1-646-402-5293 (GoogleVoice)
Re: comcast business service
On Feb 20, 2014, at 4:08 AM, shawn wilson ag4ve...@gmail.com wrote: A while ago I got Comcast's business service. Semi-idle connections are get dropped (I haven't really diagnosed this - I just no that it isn't the client or server but some network in between). However the second and most obvious issue is that intermittently, the service will grind to a halt: --- 8.8.8.8 ping statistics --- 37 packets transmitted, 34 received, 8% packet loss, time 36263ms rtt min/avg/max/mdev = 398.821/5989.160/14407.055/3808.068 ms, pipe 15 After a modem reboot, it goes normal: --- 8.8.8.8 ping statistics --- 4 packets transmitted, 4 received, 0% packet loss, time 3003ms rtt min/avg/max/mdev = 23.181/23.920/24.298/0.474 ms This seems to happen about once or twice a day. I can't attribute it to any type of traffic or number of connections. All of the rest of the network equipment is the same and the behavior persists when a computer is plugged directly into the modem. I called Comcast and they said they didn't see anything even when I was experiencing ridiculous ping times. I tend to think it's an issue with the 'modem' but I'm not sure what the issue might be or how to reproduce it when asked to if I tell them to look at it. I’ve seen this happen before with various cable ISPs. I’d concur with the poster suggesting intermittent noise on the cable segment as a likely culprit. Also if you have a cable modem that binds multiple channels for higher bandwidth this can also be problematic, especially with the noise. Signals will look good to the NOC but it’s not the signal “level that’s the issue it’s the signal to noise level. Noise has to be measured locally and techs don’t always check SNL. Also check to see if the packets aren’t actually being dropped but just taking longer than ping is looking for. Also check for out of sequence packets returned. These can indicate flapping of a bonded circuit or the bonded circuit experiencing noise. Try seeing if you disconnect everything and get a straight run to the demarc, with a know and tested out good cable, if the problem doesn’t ever occur. This could indicate noise on the cable in your premise. But I’ve experienced this same problem with noise coming through the demarc. I’ve also seen levels too hot beyond the demarc causing similar problems too. HTH. -d - Dan Shoop sh...@iwiring.net 1-646-402-5293 (GoogleVoice)
