Bret Busby wrote: > I have an external USB HDD connected to a system running Debian 6 LTS.
I don't really have any great contribution. But since no one else seems to have any good response I will contribute what I know. I have never had good luck with USB connected hard drives. They work for a while. But then invariably they get dropped offline. It might be 3-6 months between events. But for me they just are not reliable. In the past I have tried very hard to use them as system disks. Now I consider that something to avoid. I still use USB disks as "large floppies". They are still great for being large temporary data stores for holding and moving data between machines. But only when connected for short term use. Reading your problems just reinforces this belief. [On the other hand USB network devices have been rock solid for me. Meaning that while I avoid USB disks I actively use USB networking on several machines to add additional NICs. I am planning another site using additional USB NICs. It is probably hardware dependent but they have been working great for me regardless of the opposite for disks. And I have three sites using USB sound cards very robustly.] > I have tried to transfer data from the desktop intenal HDD, to the > external USB HDD. > > The file manager shows as being "Nautilus 2.30.1". I read by your message that you are a graphical desktop user. That's fine. But for transfering large amounds of data the command line tools such as rsync are the best in class. I wouldn't even consider trying to use nautilus or other graphical file managers for this type of task. I would highly recommend using rsync. Even if for you it means a stretch to get off of the mouse and over to the keyboard. The best advantage of tools such as rsync is that it is interruptable and restartable with a minimum of lost effort. I may be 1G into a 3G transfer and want to stop it, change something, and restart it again. With a normal copy that would mean copying the original data again. With rsync it means it will examine what needs to be done and be able to continue the copy using the already transfered data as done and moving forward. rsync -avP /from/here/dir-or-file /to/there/dir/ > From time to time, as in this instance, I forget (until too late) that > Debian 6 can not cope with transferring data more than about 1GB at a > time; in this instance, I had tried to transfer about 3GB, to make > room in my /home partition. Knowing how flaky USB disks interfaces tend to be I think this is most likely a hardware problem. Doesn't change your situation. But I think it blames the right thing to blame. In any case I have definitely copied gigs and gigs of data to and from USB disks. It can be very good to make large data sets portable on a portable USB drive. My complaints usually happen after the disk has been in active use as a system device for a month and then it goes offline. > The transfer had seized up, after transferring about 1.1GB of the > 3.2GB that I had tried to ransfer, so, after a couple of days of it > apparently doing nothing, I stopped it, and, as the system monitor > showed a system load of around 43 (whatever that means - if it was as > a percentage of system capacity, it could be more meaningful, to me). > The system monitor currently shows a system load average of about 35. Let me give a short explanation of system load. Which is almost impossible to say briefly so forgive me in advance for leaving out important parts, saying half of it wrong, and still saying too much. The concept is the important part here. First there is no set capacity. There isn't a cap such as 5 or 10 or 100. Therefore there isn't a way to say what percentage of your system is being used by any particular system load. But it is an important indicator of system status and health. A load of 35 or 43 are both very high system loads! The operating system process scheduler schedules processes to run. A process ready to run is queued into the run queue. If the process is calculating PI to a zillion decimal places then it is going to use 100% of the cpu until it has consumed its time slice and suspended to give the next process time to run. If there are no other proceses then the cpu will be given back to this process and the cpu will continue to be 100% utilized forever. But what about processes reading and writing to the disk drive or network? In computer speed spinning disk drives are slow. In computer speeds networks are slow. Web servers are slow. Say that your web browser sends an http GET request to a web site. It then must wait for the response. Your web browser is ready to run. But it can't. It is waiting for external events return. It is "blocked" waiting for I/O. While it is waiting the OS will schedule another process to run. If there is another process ready it will get cpu. It may also be waiting for the disk drive to spin and return data. Or spin and complete a data write. The OS will spin through the run queue running any process that is ready to run. Some will run for a short time and then perform a read or a write to an I/O device. That will cause them to stop running while their I/O request is processed. Other processes such as those running protein folding research will consume all cpu running until the OS suspends them. The OS manages the run queue and keeps things moving through the cpu using a variety of algorithms to make best use of the cpu. A system running a lot of processes where all of the processes are using 100% cpu will be very busy and feel very slow. A system running a lot of processes where most of them are waiting for some I/O to complete will be mostly idle because it will be mostly waiting and will feel very responsive. You might not even notice it is doing so many things. I hope this explains the run queue in the OS and how it is used. The run queue is the load average you are seeing. Those numbers 43 and 35 are the number of processes in the OS run queue. It says that you have forty processes in the run queue. Wow! In a typical desktop system the load average will hover near zero. That your system is so large says something is blocking those processes from completing. Your system may be very responsive if they are all waiting, if they are all "blocked waiting for I/O". Or it may be really bogged down if they are all crunching something on the cpu. Or bogged down if they are consuming too much memory and your system swaps. A high load average indicates something is blocking those processes from completing and they are stacking up in the queue. When airplanes can't land at an airport fast enough then air traffic control stacks them up in the holding patterns. That is what is being indicated by your high load average. There isn't a maximum and therefore there isn't a percentage of capacity. If you see a high load average such as that run a 'ps' command to look to see what processes are running. Sorry I don't know how to do that from a graphical desktop. But in the command line shell I would normally run: ps -efH | less # Or the bsd way: ps aux | less Then look to see what is running. If you have a load of 40 then there will be at least 40 unusual processes there. Maybe that is 40 nautilus processes stacked up trying to talk to the USB. I think that likely. That would definitely indicate a system problem talking to the USB device. You may ask, "What is an unusual process?" That is a hard one to answer. You should look at a normally running system routinely and learn what is normally running. Then later when things are not running normally you will recognize patterns that are different. For example you would probably not normally see nautilus running. Or if you have it open I expect you would see one process. But if you were to see 40 nautilus procesess then you would know that was unusual and likely an indicator of a problem. What you would do with that information depends upon the information. I would try to figure out why those processes are stacking up. I would try to clear them. That might be by removing the USB. Or by killing processes with kill. Or other things depending upon the situation. But something is wrong and it is good to know what. I don't really know what to say about the rest of your problems and situation. But I hope this small piece was helpful for this small part of it. Bob
signature.asc
Description: Digital signature
