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  • How can a single disk in a hardware SATA RAID-10 array bring the entire array to a screeching halt?

    - by Stu Thompson
    Prelude: I'm a code-monkey that's increasingly taken on SysAdmin duties for my small company. My code is our product, and increasingly we provide the same app as SaaS. About 18 months ago I moved our servers from a premium hosting centric vendor to a barebones rack pusher in a tier IV data center. (Literally across the street.) This ment doing much more ourselves--things like networking, storage and monitoring. As part the big move, to replace our leased direct attached storage from the hosting company, I built a 9TB two-node NAS based on SuperMicro chassises, 3ware RAID cards, Ubuntu 10.04, two dozen SATA disks, DRBD and . It's all lovingly documented in three blog posts: Building up & testing a new 9TB SATA RAID10 NFSv4 NAS: Part I, Part II and Part III. We also setup a Cacit monitoring system. Recently we've been adding more and more data points, like SMART values. I could not have done all this without the awesome boffins at ServerFault. It's been a fun and educational experience. My boss is happy (we saved bucket loads of $$$), our customers are happy (storage costs are down), I'm happy (fun, fun, fun). Until yesterday. Outage & Recovery: Some time after lunch we started getting reports of sluggish performance from our application, an on-demand streaming media CMS. About the same time our Cacti monitoring system sent a blizzard of emails. One of the more telling alerts was a graph of iostat await. Performance became so degraded that Pingdom began sending "server down" notifications. The overall load was moderate, there was not traffic spike. After logging onto the application servers, NFS clients of the NAS, I confirmed that just about everything was experiencing highly intermittent and insanely long IO wait times. And once I hopped onto the primary NAS node itself, the same delays were evident when trying to navigate the problem array's file system. Time to fail over, that went well. Within 20 minuts everything was confirmed to be back up and running perfectly. Post-Mortem: After any and all system failures I perform a post-mortem to determine the cause of the failure. First thing I did was ssh back into the box and start reviewing logs. It was offline, completely. Time for a trip to the data center. Hardware reset, backup an and running. In /var/syslog I found this scary looking entry: Nov 15 06:49:44 umbilo smartd[2827]: Device: /dev/twa0 [3ware_disk_00], 6 Currently unreadable (pending) sectors Nov 15 06:49:44 umbilo smartd[2827]: Device: /dev/twa0 [3ware_disk_07], SMART Prefailure Attribute: 1 Raw_Read_Error_Rate changed from 171 to 170 Nov 15 06:49:45 umbilo smartd[2827]: Device: /dev/twa0 [3ware_disk_10], 16 Currently unreadable (pending) sectors Nov 15 06:49:45 umbilo smartd[2827]: Device: /dev/twa0 [3ware_disk_10], 4 Offline uncorrectable sectors Nov 15 06:49:45 umbilo smartd[2827]: Num Test_Description Status Remaining LifeTime(hours) LBA_of_first_error Nov 15 06:49:45 umbilo smartd[2827]: # 1 Short offline Completed: read failure 90% 6576 3421766910 Nov 15 06:49:45 umbilo smartd[2827]: # 2 Short offline Completed: read failure 90% 6087 3421766910 Nov 15 06:49:45 umbilo smartd[2827]: # 3 Short offline Completed: read failure 10% 5901 656821791 Nov 15 06:49:45 umbilo smartd[2827]: # 4 Short offline Completed: read failure 90% 5818 651637856 Nov 15 06:49:45 umbilo smartd[2827]: So I went to check the Cacti graphs for the disks in the array. Here we see that, yes, disk 7 is slipping away just like syslog says it is. But we also see that disk 8's SMART Read Erros are fluctuating. There are no messages about disk 8 in syslog. More interesting is that the fluctuating values for disk 8 directly correlate to the high IO wait times! My interpretation is that: Disk 8 is experiencing an odd hardware fault that results in intermittent long operation times. Somehow this fault condition on the disk is locking up the entire array Maybe there is a more accurate or correct description, but the net result has been that the one disk is impacting the performance of the whole array. The Question(s) How can a single disk in a hardware SATA RAID-10 array bring the entire array to a screeching halt? Am I being naïve to think that the RAID card should have dealt with this? How can I prevent a single misbehaving disk from impacting the entire array? Am I missing something?

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  • "Wireless disabled by hardware switch" after suspend and other hardware buttons ineffective - how can I solve this?

    - by fahadayaz
    I have recently purchased a Novatech nFinity N1410 laptop and am having problems with the wireless, which sudo lshw -C network tells me is Centrino Wireless-N 2230 and using the iwlwifi driver. The problem is that after the device has been suspended, I am not able to get the wireless working again without a restart. The network indicator states that the wireless disabled by hardware switch. Though Fn+F2 is meant to be the wireless switch, xev tells me that the system doesn't see it as anything at all when I press this hardware combination. Also, though the brightness up/down buttons work fine, the volume up/down buttons do not work either. What can I do to fix this? I am running Ubuntu 12.10 with all available updates installed.

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  • Coherence on Exalogic: 6x Speeds on Half the Hardware is Possible

    - by jeckels
    Recently, Oracle Coherence released its 12c version, focused on scalability and real-time data delivery. As part of the launch, we showcased Coherence's tight coupling with Exalogic Elastic Cloud. By leveraging the Inifiniband Fabric in Exalogic, Coherence can now operate at up to 6x the speed on as little as half the hardware on an Exalogic box. This breakthrough is helping customers save money on their hardware costs while improving performance of their data grid. Here's a free resource available for you to explore this technology relationship further.For even more information on Coherence, attend our upcoming free virtual developer day on November 5th to see how developers can leverage Coherence in their everyday tasks.

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  • How long to install a new RAID 1 pair in linux using hardware RAID?

    - by Roger H
    Hi, I need to install a pair of 1Tb disks into a server that has a hardware RAID card. How long is it likely to take to configure the RAID controller - sticking the disks in is only a 5 minute job, but is there likely to be significant downtime while both disks mirror (even though they are both blank)? Am I looking at 10 minutes over all, or more like 2 hours for this to happen? Thanks

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  • No "Safely Remove Hardware" for USB-Connected External Hard Disk? (Windows XP)

    - by deathlock
    I have several external hard disks with different brands. Each time I connect those hard disk to my laptop (with USB), there is no option for Safely Remove Hardware / Eject. This problem only seem to occur with external hard disks, since the option is there if I connect with USB Flash Drives. Why is it happening and is there any way to enable it? What is the best method to remove an external hard disk?

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  • what is the a good hardware for a small business server? [closed]

    - by mans
    I need to setup a server for our small team. I neeed to install: 1- a version control application 2- Continus built application (the application needs to be built on windows) 3- WIKI 4- project managment software 5- issue tracking software 6- file sharing I think I need a raid 1 server for mirroring. Since it is not a database server, I am not interestred in raid 0. What is a suitable hardware for this server and where can I buy it in UK?

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  • How many layers are between my program and the hardware?

    - by sub
    I somehow have the feeling that modern systems, including runtime libraries, this exception handler and that built-in debugger build up more and more layers between my (C++) programs and the CPU/rest of the hardware. I'm thinking of something like this: 1 + 2 OS top layer Runtime library/helper/error handler a hell lot of DLL modules OS kernel layer Do you really want to run 1 + 2?-Windows popup (don't take this serious) OS kernel layer Hardware abstraction Hardware Go through at least 100 miles of circuits Eventually arrive at the CPU ADD 1, 2 Go all the way back to my program Nearly all technical things are simply wrong and in some random order, but you get my point right? How much longer/shorter is this chain when I run a C++ program that calculates 1 + 2 at runtime on Windows? How about when I do this in an interpreter? (Python|Ruby|PHP) Is this chain really as dramatic in reality? Does Windows really try "not to stand in the way"? e.g.: Direct connection my binary < hardware?

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  • Robotic Arm &ndash; Hardware

    - by Szymon Kobalczyk
    This is first in series of articles about project I've been building  in my spare time since last Summer. Actually it all began when I was researching a topic of modeling human motion kinematics in order to create gesture recognition library for Kinect. This ties heavily into motion theory of robotic manipulators so I also glanced at some designs of robotic arms. Somehow I stumbled upon this cool looking open source robotic arm: It was featured on Thingiverse and published by user jjshortcut (Jan-Jaap). Since for some time I got hooked on toying with microcontrollers, robots and other electronics, I decided to give it a try and build it myself. In this post I will describe the hardware build of the arm and in later posts I will be writing about the software to control it. Another reason to build the arm myself was the cost factor. Even small commercial robotic arms are quite expensive – products from Lynxmotion and Dagu look great but both cost around USD $300 (actually there is one cheap arm available but it looks more like a toy to me). In comparison this design is quite cheap. It uses seven hobby grade servos and even the cheapest ones should work fine. The structure is build from a set of laser cut parts connected with few metal spacers (15mm and 47mm) and lots of M3 screws. Other than that you’d only need a microcontroller board to drive the servos. So in total it comes a lot cheaper to build it yourself than buy an of the shelf robotic arm. Oh, and if you don’t like this one there are few more robotic arm projects at Thingiverse (including one by oomlout). Laser cut parts Some time ago I’ve build another robot using laser cut parts so I knew the process already. You can grab the design files in both DXF and EPS format from Thingiverse, and there are also 3D models of each part in STL. Actually the design is split into a second project for the mini servo gripper (there is also a standard servo version available but it won’t fit this arm).  I wanted to make some small adjustments, layout, and add measurements to the parts before sending it for cutting. I’ve looked at some free 2D CAD programs, and finally did all this work using QCad 3 Beta with worked great for me (I also tried LibreCAD but it didn’t work that well). All parts are cut from 4 mm thick material. Because I was worried that acrylic is too fragile and might break, I also ordered another set cut from plywood. In the end I build it from plywood because it was easier to glue (I was told acrylic requires a special glue). Btw. I found a great laser cutter service in Kraków and highly recommend it (www.ebbox.com.pl). It cost me only USD $26 for both sets ($16 acrylic + $10 plywood). Metal parts I bought all the M3 screws and nuts at local hardware store. Make sure to look for nylon lock (nyloc) nuts for the gripper because otherwise it unscrews and comes apart quickly. I couldn’t find local store with metal spacers and had to order them online (you’d need 11 x 47mm and 3 x 15mm). I think I paid less than USD $10 for all metal parts. Servos This arm uses five standards size servos to drive the arm itself, and two micro servos are used on the gripper. Author of the project used Modelcraft RS-2 Servo and Modelcraft ES-05 HT Servo. I had two Futaba S3001 servos laying around, and ordered additional TowerPro SG-5010 standard size servos and TowerPro SG90 micro servos. However it turned out that the SG90 won’t fit in the gripper so I had to replace it with a slightly smaller E-Sky EK2-0508 micro servo. Later it also turned out that Futaba servos make some strange noise while working so I swapped one with TowerPro SG-5010 which has higher torque (8kg / cm). I’ve also bought three servo extension cables. All servos cost me USD $45. Assembly The build process is not difficult but you need to think carefully about order of assembling it. You can do the base and upper arm first. Because two servos in the base are close together you need to put first with one piece of lower arm already connected before you put the second servo. Then you connect the upper arm and finally put the second piece of lower arm to hold it together. Gripper and base require some gluing so think it through too. Make sure to look closely at all the photos on Thingiverse (also other people copies) and read additional posts on jjshortcust’s blog: My mini servo grippers and completed robotic arm  Multiply the robotic arm and electronics Here is also Rob’s copy cut from aluminum My assembled arm looks like this – I think it turned out really nice: Servo controller board The last piece of hardware I needed was an electronic board that would take command from PC and drive all seven servos. I could probably use Arduino for this task, and in fact there are several Arduino servo shields available (for example from Adafruit or Renbotics).  However one problem is that most support only up to six servos, and second that their accuracy is limited by Arduino’s timer frequency. So instead I looked for dedicated servo controller and found a series of Maestro boards from Pololu. I picked the Pololu Mini Maestro 12-Channel USB Servo Controller. It has many nice features including native USB connection, high resolution pulses (0.25µs) with no jitter, built-in speed and acceleration control, and even scripting capability. Another cool feature is that besides servo control, each channel can be configured as either general input or output. So far I’m using seven channels so I still have five available to connect some sensors (for example distance sensor mounted on gripper might be useful). And last but important factor was that they have SDK in .NET – what more I could wish for! The board itself is very small – half of the size of Tic-Tac box. I picked one for about USD $35 in this store. Perhaps another good alternative would be the Phidgets Advanced Servo 8-Motor – but it is significantly more expensive at USD $87.30. The Maestro Controller Driver and Software package includes Maestro Control Center program with lets you immediately configure the board. For each servo I first figured out their move range and set the min/max limits. I played with setting the speed an acceleration values as well. Big issue for me was that there are two servos that control position of lower arm (shoulder joint), and both have to be moved at the same time. This is where the scripting feature of Pololu board turned out very helpful. I wrote a script that synchronizes position of second servo with first one – so now I only need to move one servo and other will follow automatically. This turned out tricky because I couldn’t find simple offset mapping of the move range for each servo – I had to divide it into several sub-ranges and map each individually. The scripting language is bit assembler-like but gets the job done. And there is even a runtime debugging and stack view available. Altogether I’m very happy with the Pololu Mini Maestro Servo Controller, and with this final piece I completed the build and was able to move my arm from the Meastro Control program.   The total cost of my robotic arm was: $10 laser cut parts $10 metal parts $45 servos $35 servo controller ----------------------- $100 total So here you have all the information about the hardware. In next post I’ll start talking about the software that I wrote in Microsoft Robotics Developer Studio 4. Stay tuned!

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  • How to diagnose and fix Kernel Panic Fatal Machine Check error?

    - by 0x4a6f4672
    I have got a new Samsung Series 7 laptop with dual boot setup for Windows 8 and Ubuntu 12.10. A fine machine comparable to a Macbook Pro. The Ubuntu installation was quite a hassle, but with the help of Boot Repair finally it seemed to work. Or so I thought. Windows 8 starts fine, but if I want to start Ubuntu regularly the following Machine Check Exception error occurs, quite similar to this one [Hardware Error] CPU 1: Machine Check Exception: 5 Bank 6 [Hardware Error] RIP !inexact! 33 <00007fab2074598a> [Hardware Error] TSC 95b623464c ADDR fe400 MISC 3880000086 .. [similar messages for CPU 2,3 and 0] .. [Hardware Error] Machine Check: Processor context corrupt Kernel panic - not syncing: Fatal Machine Check Rebooting in 30 seconds Kernel panic does not sound good. Then it starts to reboot, and the second boot trial often works. Is it a Kernel or driver problem? The laptop has an Intel Core i7 processor. I already deactivated Hyperthreading in the BIOS, but it does not seem to help :-( I also disabled the Execute Disable Bit (EDB) flag in the BIOS. EDB is an Intel hardware-based security feature that can help reduce system exposure to viruses and malicious code. Since I disabled it, the error did occur less frequently, but it still appears occasionally :-( It seems to be the same error as described here and here. Maybe a Samsung specific Kernel problem? A similar error also happens on a Samsung Ultrabook Series 9 (which seems to be kernel bugs 49161 and 47121). At my Samsung Series 7, it still occurs for instance during booting on battery after "Checking battery state". Perhaps anyone else has an idea? These Kernel Panic errors are reallly annoying..

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  • Kernel Panic Fatal Machine Check

    - by 0x4a6f4672
    I have got a new Samsung Series 7 laptop with dual boot setup for Windows 8 and Ubuntu 12.10. The Ubuntu installation was quite a hassle, but with the help of Boot Repair finally it seemed to work. Or so I thought. Windows 8 starts fine, but if I want to start Ubuntu regularly the following error occurs, quite similar to this one [Hardware Error] CPU 1: Machine Check Exception: 5 Bank 6 [Hardware Error] RIP !inexact! 33 <00007fab2074598a> [Hardware Error] TSC 95b623464c ADDR fe400 MISC 3880000086 .. [similar messages for CPU 2,3 and 0] .. [Hardware Error] Machine Check: Processor context corrupt Kernel panic - not syncing: Fatal Machine Check Rebooting in 30 seconds Kernel panic does not sound good. Then it starts to reboot, and the second boot trial often works. Is it a Kernel or driver problem? The laptop has an Intel Core i7 processor. I already deactivated Hyperthreading in the BIOS, but it does not seem to help :-(

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  • When should I decline to make a requested change?

    - by reuscam
    I work on the software side of a company that provides custom hardware with software running on top of it. Often times the hardware is not engineered well. In those cases, I am often asked first to troubleshoot the problem - of course the symptom is always "your software crashed" or something along those lines. Just recently we had another one of these incidents where power on a USB line is not reliable, and it causes a USB device to fail. This causes a usability problem in one of our applications. I have been asked by upper management to handle this better - continually monitor the USB device, and if it disappears, then reboot, or try to reset it. Doing either of these is not guaranteed to fix anything. Ultimately, the real fix is to correct the reliability of the device from the hardware side. I could improve performance, but not to 100%, and of course I would be using my already limited time to bloat code and add yet another device monitoring thread. So with all that said, how do I make a good decision about when to say that this needs to be a hardware fix, and only a hardware fix? Can I approach this quantitatively, and come up with some sort of definitive yes/no test? I'm sure its not that easy.

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  • Software RAID to hardware RAID, can it be done?

    - by gtaylor85
    Can it be done ... well. (For the record, I did not set this server up.) In my server there are 4 disks. 3 of them are in a software RAID5, and 1 has the OS installed. I want to buy a RAID controller, 4 new HDs and set up a hardware RAID5. If possible, I'd like to just image the current setup, and use it to build my new one. My questions are: Can I image a 3 disk RAID5 to 4 disk RAID5? Are there problems with this? What is considered best practice for your OS. To have it on a separate disk like it currently is, or to install it on the RAID5? Thank you. I can clarify anything. I'm not sure what other info might be pertinent.

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  • How to figure out if hardware is slower than it should be?

    - by paldepind
    I'm pretty sure that my computer is slower than it should be and it has been that since a got it. For instance it lags a lot in Counter Strike Source. And yes I've installed all the newest drivers. And it doesn't matter what OS I uses. I've tried both Windows, Linux and FreeBSD and it's slow in all of them. So what could this be? Is there something wrong with the hardware? And if, then what could it be?

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  • How do I configure hardware raid in a Poweredge 2850?

    - by Eric Fossum
    I just bought a Dell Poweredge 2850 from Craigslist and for the most part I'm happy with it's $300 price-tag, but I cannot figure out where to configure the embedded hardware raid... I've seen online you should hit <CTRL-M>, but while booting my box never says that. I have <CTRL-A> (I think) for an LSI Logic config, but that seems to just program SCSI and verify drives on my SCSI-A and SCSI-B. Anyone have a clue where this RAID config is?

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  • Recommendation for hardware upgrade: thin clients? Or...?

    - by Alex C.
    I work for an animal shelter in Upstate New York. We have about 50 machines running XP Pro. They're connected to a Windows network with a domain. About half of these computers are used for nothing more than using two web-based apps -- one to keep track of our animals, the other to process credit cards. Having a full-blown desktop PC seems like overkill for this purpose. The PCs are three-to-five years old, and I'd like to come up with a plan to upgrade the hardware. Our donations are down (not surprising, given the economy), so cost is a big factor. Can people recommend some options? Some sort of thin client, maybe?

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  • Partner WebCasts: EMEA Alliances and Channels Hardware Webinars, July 2012

    - by rituchhibber
    Dear partner Oracle is pleased to invite you to the following webcasts dedicated to our EMEA partner community and designed to provide you with important news on our SPARC and Storage product portfolios. Please ensure you don't miss these unique learning opportunities! 1. How to Make Money Selling SPARC! 3PM CET (2pm UKT), Tuesday, July 10, 2012 The webcast will be hosted by - Rob Ludeman, from SPARC Product Management, and Thomas Ressler, WWA&C Alliances Consultant. Agenda: To bring our partners timely, valuable information, focused on increase in their success during selling SPARC systems. The webcast will be focused and targeted on specific topics and will last approximately in 30 minutes.You can submit your questions via WebEx chat and there will be a live Q&A session at the end of the webcast. REGISTER NOW 2. Introduction to Oracle’s New StorageTek SL150 Modular Tape Library 3pm CET (2pm UK), Thursday, July 12, 2012 This webcast will help you to understand Oracle's New StorageTek SL150 Modular tape library which is the first scalable tape library designed for small and midsized companies that are experiencing high growth. Built from Oracle software and StorageTek library technology, it delivers a cost-effective combination of ease of use and scalability, resulting in overall TCO savings. During the webcast Cindy McCurley, from Tape Product Management will introduce you to the latest addition to the Oracle Tape Storage product portfolio, the SL150 Modular Tape Library. This 60 minutes webcast will cover the product’s features, positioning, unique selling points and a competitive overview on StorageTek. You can submit your questions via WebEx chat and there will be a live Q&A session at the end of the webcast. REGISTER NOW Delivery Format This FREE online LIVE eSeminar will be delivered over the Web and Conference Call. Note: Please join the call 10 minutes before the scheduled start time. We look forward to your participation. Best regards, Giuseppe Facchetti EMEA Partner Business Development Manager, Oracle Hardware Sales Sasan Moaveni EMEA Storage Sales Manager, Oracle Hardware Sales

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  • Oracle Key Vault - Hardware Security Modul für TDE und mehr

    - by Heinz-Wilhelm Fabry (DBA Community)
    Anfang August hat Oracle ein neues Produkt namens Oracle Key Vault (OKV) zum Einsatz freigegeben. Es handelt sich dabei um ein Hardware Security Modul (HSM) - also um ein Stück Hardware zum Speichern von Schlüsseln, Passwörtern und Dateien, die Schlüssel und Passwörter enthalten. Oracle Datenbank Installationen nutzen die zuletzt genannte Form des Speicherns von Passwörtern und Schlüsseln in Dateien für Oracle Advanced Security Transparent Data Encryption (TDE) und external password stores. Die Dateien werden in den Versionen 10 und 11 der Datenbank als Wallets bezeichnet, in der Version 12 als Keystores. Allerdings gibt es auch schon seit der Datenbankversion 11.2 beim Einsatz von TDE die Möglichkeit, statt der Wallets / Keystores HSMs einzusetzen. Da Oracle selbst kein eigenes HSM Produkt anbieten konnte, haben Unternehmenskunden dann auf Produkte anderer Anbieter zurückgegriffen. Das kann sich mit OKV nun ändern. Abhängig vom Bedrohungsszenario kann die Entscheidung gegen den Einsatz von Wallets / Keystores und für den Einsatz eines HSMs durchaus sinnvoll sein, denn ein HSM bietet mehr Sicherheit: Eine Betriebssystemdatei kann leichter gestohlen (kopiert) werden, als ein HSM, das in der Regel als speziell gesicherte Steckkarte in einem Rechner eingebaut ist oder als eigenes Gerät geschützt in einem Rechenzentrum steht. ein HSM kann anders als ein Wallet / Keystore systemübergreifend verwendet werden. Das erlaubt eine gemeinsame Nutzung von Schlüsseln - was wiederum zum Beispiel den Einsatz von TDE auf RAC Installationen perfekt unterstützt. ein HSM kann von mehreren Anwendungen genutzt werden. Das erleichtert das Konsolidieren und Verwalten von Passwörtern und Schlüsseln. Im aktuellen Tipp wird als Einführung in das neue Produkt dargestellt, wie OKV für TDE genutzt werden kann.

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  • ATI Catalyst driver 12.8 is not using hardware acceleration on Precise

    - by Jack Wright
    I've been using Ubuntu and ATI Catalyst for years. On my clean install of Ubuntu 12.04 I've noticed that Catalyst 12.6 and then 12.8 are not actually using my HD5750 GPU for hardware acceleration - high CPU usage, zero GPU load. Everything installed correctly with no hassles, fglrxinfo and vainfo are correct as per this HowTo for Precise. I have an Ubuntu 10.04 with Catalyst 12.6 installation on the same hardware which does use the GPU - low CPU usage, high GPU load when transcodeing video files or playing video content. The VA-API drivers are not installed on the 10.04 build. They are not mentioned in this HowTo for Lucid. fgl_glxgears frame rates on Precise are a fifth of the rates on Lucid. LUCID jw@Kworld:~$ fgl_glxgears Using GLX_SGIX_pbuffer 16867 frames in 5.0 seconds = 3373.400 FPS 12523 frames in 5.0 seconds = 2504.600 FPS 13763 frames in 5.0 seconds = 2752.600 FPS PRECISE jw@NewWorld12:~$ fgl_glxgears Using GLX_SGIX_pbuffer 12905 frames in 5.0 seconds = 2581.000 FPS 3230 frames in 5.0 seconds = 646.000 FPS 517 frames in 5.0 seconds = 103.400 FPS 518 frames in 5.0 seconds = 103.600 FPS 6489 frames in 5.0 seconds = 1297.800 FPS This is glxgears running in fullscreen. In Lucid (10.04) I can't see the gears, they are spinning so fast, but in Precise (12.04) they are really sluggish. Has anyone else noticed a problem like this? Cheers, Jack.

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  • Threading models when talking to hardware devices

    - by Fuzz
    When writing an interface to hardware over a communication bus, communications timing can sometimes be critical to the operation of a device. As such, it is common for developers to spin up new threads to handle communications. It can also be a terrible idea to have a whole bunch of threads in your system, an in the case that you have multiple hardware devices you may have many many threads that are out of control of the main application. Certainly it can be common to have two threads per device, one for reading and one for writing. I am trying to determine the pros and cons of the two different models I can think of, and would love the help of the Programmers community. Each device instance gets handles it's own threads (or shares a thread for a communication device). A thread may exist for writing, and one for reading. Requested writes to a device from the API are buffered and worked on by the writer thread. The read thread exists in the case of blocking communications, and uses call backs to pass read data to the application. Timing of communications can be handled by the communications thread. Devices aren't given their own threads. Instead read and write requests are queued/buffered. The application then calls a "DoWork" function on the interface and allows all read and writes to take place and fire their callbacks. Timing is handled by the application, and the driver can request to be called at a given specific frequency. Pros for Item 1 include finer grain control of timing at the communication level at the expense of having control of whats going on at the higher level application level (which for a real time system, can be terrible). Pros for Item 2 include better control over the timing of the entire system for the application, at the expense of allowing each driver to handle it's own business. If anyone has experience with these scenarios, I'd love to hear some ideas on the approaches used.

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