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  • Best (Java) book for understanding 'under the bonnet' for programming?

    - by Ben
    What would you say is the best book to buy to understand exactly how programming works under the hood in order to increase performance? I've coded in assembly at university, I studied computer architecture and I obviously did high level programming, but what I really dont understand is things like: -what is happening when I perform a cast -whats the difference in performance if I declare something global as opposed to local? -How does the memory layout for an ArrayList compare with a Vector or LinkedList? -Whats the overhead with pointers? -Are locks more efficient than using synchronized? -Would creating my own array using int[] be faster than using ArrayList -Advantages/disadvantages of declaring a variable volatile I have got a copy of Java Performance Tuning but it doesnt go down very low and it contains rather obvious things like suggesting a hashmap instead of using an ArrayList as you can map the keys to memory addresses etc. I want something a bit more Computer Sciencey, linking the programming language to what happens with the assembler/hardware. The reason im asking is that I have an interview coming up for a job in High Frequency Trading and everything has to be as efficient as possible, yet I cant remember every single possible efficiency saving so i'd just like to learn the fundamentals. Thanks in advance

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  • lapply slower than for-loop when used for a BiomaRt query. Is that expected?

    - by ptocquin
    I would like to query a database using BiomaRt package. I have loci and want to retrieve some related information, let say description. I first try to use lapply but was surprise by the time needed for the task to be performed. I thus tried a more basic for-loop and get a faster result. Is that expected or is something wrong with my code or with my understanding of apply ? I read other posts dealing with *apply vs for-loop performance (Here, for example) and I was aware that improved performance should not be expected but I don't understand why performance here is actually lower. Here is a reproducible example. 1) Loading the library and selecting the database : library("biomaRt") athaliana <- useMart("plants_mart_14") athaliana <- useDataset("athaliana_eg_gene",mart=athaliana) 2) Querying the database : loci <- c("at1g01300", "at1g01800", "at1g01900", "at1g02335", "at1g02790", "at1g03220", "at1g03230", "at1g04040", "at1g04110", "at1g05240" ) I create a function for the use in lapply : foo <- function(loci) { getBM("description","tair_locus",loci,athaliana) } When I use this function on the first element : > system.time(foo(cwp_loci[1])) utilisateur système écoulé 0.020 0.004 1.599 When I use lapply to retrieve the data for all values : > system.time(lapply(loci, foo)) utilisateur système écoulé 0.220 0.000 16.376 I then created a new function, adding a for-loop : foo2 <- function(loci) { for (i in loci) { getBM("description","tair_locus",loci[i],athaliana) } } Here is the result : > system.time(foo2(loci)) utilisateur système écoulé 0.204 0.004 10.919 Of course, this will be applied to a big list of loci, so the best performing option is needed. I thank you for assistance. EDIT Following recommendation of @MartinMorgan Simply passing the vector loci to getBM greatly improves the query efficiency. Simpler is better. > system.time(lapply(loci, foo)) utilisateur système écoulé 0.236 0.024 110.512 > system.time(foo2(loci)) utilisateur système écoulé 0.208 0.040 116.099 > system.time(foo(loci)) utilisateur système écoulé 0.028 0.000 6.193

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  • Phonegap: Will my mobile app 'feel' faster or slower once ported to phonegap?

    - by user15872
    So I'm designing everything in mobile Safari and I know that phonegap is essentially a stripped webview but... Question: Will my application will run better in phonegap? (revised below) a)I imagine my navigation and core app will load faster as the scripts and images are on the hard drive. Is this True? b)I assume since they've been working on it for 2 years now that they may have made some optimizations to make it quicker than just an average safari window. Is this true? (Assuming both html5/js/css code bases are pretty much the same and app is running on iOS.) Update: Sorry, I meant to compare apples to slightly different apples. Question 1 revised: Will my app see any performance benefits running with in a phonegap environment vs standard mobile safari? (compare mobile - to mobile) 1b) In what ways, other than loading time has phonegap optimized performance over standard mobile safari? Follow ups: 1) Are there any pitfalls, other than large libraries, that may cause phonegap to suffer a serious performance hit vs stand mobile safari? 2) Can I mix native and webview rendering? (i.e the top half of my app is rendered in with html/css/js and the bottom half native)

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  • Emacs: Often switching between Emacs and my IDE's editor, how can I 'synch' the file?

    - by WizardOfOdds
    I very often need to do some Emacs magic on some files and I need to go back and forth my IDE (IntelliJ IDEA) and Emacs. When a change is made under Emacs (and after I've saved the file) and I go back to IntelliJ the change appears immediately (if I recall correctly I configured IntelliJ to "always reload file when a modification is detected on disk" or something like that). I don't even need to reload: as soon as IntelliJ IDEA gains focus, it instantly reloads the file (and I hence have immediately access to the modifications I made from Emacs). So far, so very good. However "the other way round", it doesn't work yet. Can I configure Emacs so that everytime a file is changed on disk it reloads it? Or make Emacs, everytime it "gains focus", verify if any file currently opened has been modified on disk? I know I can start modifying the buffer under Emacs and it shall instantly warn that it has been modified, but I'd rather have it do it immediately (for example if I used my IDE to do some big change, when I come back to Emacs what I see may not be at all anymore what the file contains and it's a bit weird).

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  • Why use shorter VARCHAR(n) fields?

    - by chryss
    It is frequently advised to choose database field sizes to be as narrow as possible. I am wondering to what degree this applies to SQL Server 2005 VARCHAR columns: Storing 10-letter English words in a VARCHAR(255) field will not take up more storage than in a VARCHAR(10) field. Are there other reasons to restrict the size of VARCHAR fields to stick as closely as possible to the size of the data? I'm thinking of Performance: Is there an advantage to using a smaller n when selecting, filtering and sorting on the data? Memory, including on the application side (C++)? Style/validation: How important do you consider restricting colunm size to force non-sensical data imports to fail (such as 200-character surnames)? Anything else? Background: I help data integrators with the design of data flows into a database-backed system. They have to use an API that restricts their choice of data types. For character data, only VARCHAR(n) with n <= 255 is available; CHAR, NCHAR, NVARCHAR and TEXT are not. We're trying to lay down some "good practices" rules, and the question has come up if there is a real detriment to using VARCHAR(255) even for data where real maximum sizes will never exceed 30 bytes or so. Typical data volumes for one table are 1-10 Mio records with up to 150 attributes. Query performance (SELECT, with frequently extensive WHERE clauses) and application-side retrieval performance are paramount.

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  • Dealing with large number of text strings

    - by Fadrian
    My project when it is running, will collect a large number of string text block (about 20K and largest I have seen is about 200K of them) in short span of time and store them in a relational database. Each of the string text is relatively small and the average would be about 15 short lines (about 300 characters). The current implementation is in C# (VS2008), .NET 3.5 and backend DBMS is Ms. SQL Server 2005 Performance and storage are both important concern of the project, but the priority will be performance first, then storage. I am looking for answers to these: Should I compress the text before storing them in DB? or let SQL Server worry about compacting the storage? Do you know what will be the best compression algorithm/library to use for this context that gives me the best performance? Currently I just use the standard GZip in .NET framework Do you know any best practices to deal with this? I welcome outside the box suggestions as long as it is implementable in .NET framework? (it is a big project and this requirements is only a small part of it) EDITED: I will keep adding to this to clarify points raised I don't need text indexing or searching on these text. I just need to be able to retrieve them in later stage for display as a text block using its primary key. I have a working solution implemented as above and SQL Server has no issue at all handling it. This program will run quite often and need to work with large data context so you can imagine the size will grow very rapidly hence every optimization I can do will help.

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  • jQuery trigger function on change

    - by Michael Pasqualone
    I have the following two slider functions which work well and display like so: I have diskAmount and transferAmount stored in global vars, however what I am now trying to figure out is how do I get the sum of the two to initially show as the monthly fee, and then update when either of the two sliders are changed. So in my screenshot above the initial state will be $24.75, and the fee will update if the sliders change. Can anyone point me in the right direction? I get can the initial fee to show, but can't figure out how to get 1 function to call another function within jQuery. $(function() { $("#disk").slider({ value:3, min: 1, max: 80, step: 1, slide: function(event, ui) { $("#diskamount").val(ui.value + ' Gb'); $("#diskamountUnit").val('$' + parseFloat(ui.value * diskCost).toFixed(2)); } }); // Set initial diskamount state $("#diskamount").val($("#disk").slider("value") + ' Gb'); // Set initial diskamountUnit state diskAmount = $("#disk").slider("value") * diskCost; $("#diskamountUnit").val('$' + diskAmount.toFixed(2)); }); $(function() { $("#data").slider({ value:25, min: 1, max: 200, step: 1, slide: function(event, ui) { $("#dataamount").val(ui.value + ' Gb'); $("#dataamountUnit").val('$' + parseFloat(ui.value * transferCost).toFixed(2)); } }); // Set initial dataamount state $("#dataamount").val($("#data").slider("value") + ' Gb'); // Set initial dataamountUnit state transferAmount = $("#data").slider("value") * transferCost; $("#dataamountUnit").val('$' + transferAmount.toFixed(2)); });

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  • SQL Server: Why use shorter VARCHAR(n) fields?

    - by chryss
    It is frequently advised to choose database field sizes to be as narrow as possible. I am wondering to what degree this applies to SQL Server 2005 VARCHAR columns: Storing 10-letter English words in a VARCHAR(255) field will not take up more storage than in a VARCHAR(10) field. Are there other reasons to restrict the size of VARCHAR fields to stick as closely as possible to the size of the data? I'm thinking of Performance: Is there an advantage to using a smaller n when selecting, filtering and sorting on the data? Memory, including on the application side (C++)? Style/validation: How important do you consider restricting colunm size to force non-sensical data imports to fail (such as 200-character surnames)? Anything else? Background: I help data integrators with the design of data flows into a database-backed system. They have to use an API that restricts their choice of data types. For character data, only VARCHAR(n) with n <= 255 is available; CHAR, NCHAR, NVARCHAR and TEXT are not. We're trying to lay down some "good practices" rules, and the question has come up if there is a real detriment to using VARCHAR(255) even for data where real maximum sizes will never exceed 30 bytes or so. Typical data volumes for one table are 1-10 Mio records with up to 150 attributes. Query performance (SELECT, with frequently extensive WHERE clauses) and application-side retrieval performance are paramount.

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  • Unable to install Windows 2008R2 x64 on HP ProLiant ML 150 G6 with Smart Array B110i

    - by lrosa
    I am installing Windows 2008 R2 x64 (Microsoft OEM version) on a ProLint ML 150 with Smart Array B110i controller. I load the B110i drivers from a USB thumbdrive, Windows Setup can create, delete and format correctly the partitions on the raidset, but when I exit the disk manager to start setup, Windows says that he cannot find a primary partition to install Windows. The EasySetup disk provided with the system does not support Windows 2008 R2 x64 Microsoft OEM. I downloaded the latest version of EasySetup from HP website, but does not support Windows 2008 R2 x64 Microsoft OEM. Any suggestion?

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  • PERC H710 mini raid controller advanced settings (BIOS)

    - by gregg
    I upgraded from a PERC h310 to an H710 controller on my Dell R620 but didnt get any increase in performance. This is a ESXi host with a 5 disk RAID 5. I noticed when going to the RAID BIOS that the advanced settings section was not activated/checked off. In that section is the strip element size: 64kb (default) read policy: no read ahead and the write policy: write-through. Will checking that section do any harm to the existing raid array or will it simply enable those policies and hopefully boost performance? Or, lastly, is it already using those policies and the checkmark is simply to activate them for changes

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  • CHKDSK error code 766f6c756d652e63 3f1

    - by BenjiWiebe
    On a Windows 7 computer, running chkdsk /r /f C: in repair mode, it gives the error, Unspecified error 766f6c756d652e63 3f1. or something like that. I have tried the following: uninstalling all antivirus software scanning with MalwareByte's Anti-Malware doing a Disk Cleanup running Disk Defrag booting TRK and running fsck -t ntfs (gives error Unsupported case. and not implemented). I have also tried a System Restore, but there is a Temporary Internet file that appears to be in all restore points, and that file must be corrupted or something, because System Restore always grinds to a halt when it gets to that file. What should I try next? Thanks in advance.

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  • Migration of VM from Hyper-V to Hyper-V R2 - Pass through disks

    - by Andrew Gillen
    I am trying to migrate a VM which is using two pass through disks from a legacy Hyper-V Cluster to a new R2 cluster. The migrated VM cannot use the pass through disks though. The guest OS (2008 R2) doesn't seem to like the disk and eventually tries to format the disk instead of mounting it. The migration process I have been using for all my VMs is to export the VM to a new lun, then add that new lun to the new cluster, importing the vm off it in the hyper-v console, then making it highly available. I assumed I could do the same thing and just add the two pass through disks to the new cluster and then attach them inside Hyper-V. Is there a process I need to follow to migrate pass through disks that does not involve setting up new Luns and robocopying the data over?

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  • Can the Dell PowerEdge T320 boot from a USB stick in hard drive emulation mode?

    - by Icydog
    I am trying to install FreeNAS on a Dell PowerEdge T320. I've followed the instructions here (http://doc.freenas.org/index.php/Burning_an_IMG_File) to write the .img file to four different USB sticks with dd if=FreeNAS-9.2.1.5-RELEASE-x64.img of=/dev/sde, but I can't boot off of any of them. When I try to boot, I get the following screen: F1 FreeBSD F2 FreeBSD F3 Drive 0 Then it auto-selects F1 and either prints # about once a second forever, or it sits with a blinking cursor doing nothing. Forum posts and the wiki page linked above say to set the USB boot emulation mode to hard disk (as opposed to auto or CD/DVD/floppy), and older Dell PowerEdge models including the T310 have this option in the BIOS settings, but I cannot find it on the T320 with the latest BIOS 2.1.2. I have even tried writing the USB image to a USB hard disk, but with the same lack of success. Has anyone been able to find this USB boot setting on a T320, or been able to boot FreeNAS/FreeBSD from USB in some other way on a T320?

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  • Uninstalling Vista from dual boot of Win7/Vista

    - by Alex
    Topic title says it all. Right now I have 2 things I need to do... 1) Remove the windows.old folder. My problem with this is that when I go to disk cleanup, the "Remove Previous Window Installations" option isn't there. Not sure what to do here. EDIT: Solved this part. Didn't hit button clean up system files, was just looking at normal disk cleanup window. 2) The rest.. I've read that I should use EasyBCD, but I'm not sure what to do with it once I get it. Any help is appreciated. Thanks. EDIT: I downloaded EasyBCD, and I see the option to add/delete entries. Do I just need to delete the Vista entry, or is there more to it than that?

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  • Intel® Core™2 Duo Desktop Processor vs Intel® Core™ i3 Desktop Processor?

    - by metal gear solid
    Intel® Core™2 Duo Desktop Processor vs Intel® Core™ i3 Desktop Processor? Which CPU is better to buy ? Intel® Core™ i3-530 Processor (4M Cache, 2.93 GHz) (it supports DDR3 also) or Intel® Core™2 Duo Processor E7500 (3M Cache, 2.93 GHz, 1066 MHz FSB) (it supports DDR2 only ) Although I do not play games on my PC but I need good performance in Adobe Photoshop, Watching Full HD Movies. I need good performance in Multitasking. Along with any of these CPU I would purchase 2 GB x 2 stick of RAM. and I will use Windows 7. and I will use Microsoft VPC images also with MS Virtual PC.

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  • Windows 7 installation too slow

    - by BizApps
    I have P.C with Emaxx Motherboard : emx-a55gm-icafe with AMD dual core processor,500 GB WD Sata HDD,2GB of RAM,samsung dvdr,windows 7 dvd which is all brandnew. When i was trying to install windows 7 ulitmate on my P.C it really takes hours on setting up, which is really rare and i'm still hopeless getting a solution for this.But I don't have any issue installing windows 7 on my HP laptop that can be finished within just more than 20minutes. There is same issue that ive search in google and disabling the floppy disk drive in BIOS is their solution, but my problem is, Emaxx icafe doesnt have floppy disk drive setting on bios. I already change ACHI/IDE Support but i have still no luck. Is there any solution for this? Thanks in Regards

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  • How to check CPU temperature on a HP P2000?

    - by Pavel
    I have a HP StorageWorks MSA Storage P2000 G3 SAS. show sensor-status gives something like # show sensor-status Sensor Name Value Status ---------------------------------------------------- On-Board Temperature 1-Ctlr A 53 C OK On-Board Temperature 1-Ctlr B 52 C OK On-Board Temperature 2-Ctlr A 61 C OK On-Board Temperature 2-Ctlr B 63 C OK On-Board Temperature 3-Ctlr A 53 C OK On-Board Temperature 3-Ctlr B 53 C OK Disk Controller Temp-Ctlr A 34 C OK Disk Controller Temp-Ctlr B 32 C OK Memory Controller Temp-Ctlr A 66 C OK Memory Controller Temp-Ctlr B 67 C OK [...] Overall Unit Status OK OK Temperature Loc: upper-IOM A 40 C OK Temperature Loc: lower-IOM B 38 C OK Temperature Loc: left-PSU 36 C OK Temperature Loc: right-PSU 40 C OK [...] is one of the values the CPU/FPGA temperature? Or, if not, how do I get it? Thanks!

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  • Install Additional Printer Drivers (x86) on Vista (x64) - Can't find suitable (x86) ntprint.inf

    - by jmohr
    I have a printer connected to my computer that I'd like to share on my home network - shouldn't be a problem. The computer the printer is connected to is running Vista Ultimate x64. The computers I'm trying to share with are x86 Windows XP Professional and x86 Vista, so I need to install additional (x86) drivers. I checked the box to add x86 printer drivers and then it asked for the location of the drivers. I browsed to the location and clicked OK. It then prompted "Please provide path to Windows media (x86 processor). When I click "Browse..." it wants the location of a file named ntprint.inf It looks like it's asking for a Windows (x86) installation disk. I put one in but I can't seem to find this file on the 32-bit Vista install disk Where is the proper place to find this file?

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  • inaccessible_boot_device after p2v Windows 2000 Pro SP4 to Workstation 6.5

    - by 20th Century Boy
    I am using the latest VMware Converter Standalone to p2v a physical Windows 2000 Professional SP4 PC. The PC is a standard Pentium with IDE disk from circa 2001. The disk is 20GB partitioned logically into C: and D. It converts with no errors (I did both disks into one VMDK). When I power on the VM in VMware Workstation 6.5 (or Vmware Player 2.5) it gets to the Win 2000 boot graphic then I get a BSOD with the classic 0x7B Stop error: inaccessible_boot_device. Is there anything I can do to get the vm to boot? I am lost for ideas, normally p2v of a basic IDE pc works flawlessly. I'm willing to put a bounty on this as I am trying to sort this out for a client urgently.

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  • Can´t install OS from usb flash drive

    - by Bibo
    My previous problem was describe here: Can't boot OS from USB drive, showing black screen with blinking cursor and there are informations about my laptot. So please look there and then read rest here. I changed flash drive and it fix the problem but now when I boot to Ubuntu (or I tried Fedora, it do same) I can´t install system. I click on Install Ubuntu 10.10 I choose language, then on next window I click Forward but it just show waiting cursor and nothing happen (same Fedora). It doesn´t freeze so I can end install and I can take printscreen (when I was taking the screen, cursor was shown as waiting, not normal as in picture, it´s weird). Image where my installation ends I think there is some problem with Disk and Volumes and so. But I used chkdsk from W7 on boot and It said everything all right and I try utility in Ubuntu and check file system and it is all right too.Image with my Disk (Volumes and other things) I hope someone helps me. Thank you

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  • Remove automatic Aero disabling in Windows 7

    - by Jani Hartikainen
    Sometimes when I'm playing games which are heavy on the GPU, Windows decides to helpfully disable aero, causing everything to freeze for a bit and in the worst case, combined with ATI's brilliant drivers, causes the game to crash. So, How do I stop Windows from automatically disabling Aero when playing games? It has absolutely no effect on the performance of the game itself when it does that. Also, I'd like to get rid of the "You should disable Aero to improve performance" helpful hint popup which sometimes shows up. But I suppose getting rid of the first will get rid of the second, assuming anyone knows how.

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  • Windows 2k3 server as a KVM client

    - by Peter NUnn
    Just wondering if anyone else has had issues installing Windows 2K3 server under KVM. I have tried a few times tonight and keep getting "not a supported platform" when the installation first boots. I've used i686, had acpi and apic off and on, given it 4GB ram, 200GB hard disk and it fails every time. I've done some hunting around, but can't find anything conclusive on google. It is listed as a supported client on the KVM site. Host is Ubuntu 10.04 64Bit, qemu-kmv hypervisor. Drivers, I'm not sure what your asking for there, but the disk is a standard (I believe) 32 bit Win2K3 server. I'm trying to install a bulk standard server install. I've done it with win2K8 no problems, but this 2k3 install is failing every time.

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  • Cannot connect to Xen domU via VNC if X isn't installed on domU

    - by Hai Minh Nguyen
    I'm trying to build a Xen domU that can be connected through the Xen's VNC server. Below is the template (actually it's generated by OpenNebula): name = 'one-153' #O CPU_CREDITS = 256 memory = '128' bootloader = "/usr/bin/pygrub" disk = ['tap:aio:/home/oneadmin/cloud/one/var/153/images/disk.0,xvda,w',] vif = ['mac=02:00:c0:a8:00:03,bridge=virbr0',] vfb = ['type=vnc,vnclisten=slave1,vncdisplay=1,vncpasswd=v98KXdFN'] The problem is that I can't connect to the domU if it doesn't have X. In this case all I got is a blank screen. Besides, if the domU has X, the screen is still blank until the login prompt appears, while it should be like this. Some information that may be useful: The domU and the dom0 both run CentOS 5.5. If the domU has X, it can be connected even when both X and the domU's VNC server isn't running. The VNC client is RealVNC.

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  • how to multi-boot/upgrade linux from LVM-based partition

    - by kenny-bobby
    i currently have FC3 linux which installed itself on the hard disk using LVM partitioning, so it is basically all one big partition. i would like to try some other distributions and upgrade to something newer, but don't want to lose my current capabilities and data files, and i know nothing or less about LVM. Is it possible (and if so an example would be nice) to install a non-LVM-based distribution on the LVM disk and have multi-boot options? Or do i have to start over new and drop the LVM? My guess is that i should save my /home (data files and .rc files) on a backup device first, then somewhere/somehow create a new partion for installing another distribution. Any LVM experts out there that have tried anything like this--well i sure could use some pointers and advice...

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  • amanda backup problem

    - by hossam alkhalili
    hello, i installed amanda on centos 5.5 to backup windows 7 and windows server 2008 over network and i used 15 minutes instillation guide but when i type amcheck DailySet1 i got request failed then if i type amservice when i amandabackup account to define the problem i got Permission denied and on root account i got OPTIONS features=ff7fffff9cfeffffd3cf1300; i use zwc on windows 7 as an agent can anyone help me thanks -sh-3.2$ amcheck DailySet1 Amanda Tape Server Host Check Holding disk /dumps/amanda: 1791315968 KB disk space available, using 1791213568 KB slot 1: volume 'DailySet1-01' Will write to volume 'DailySet1-01' in slot 1. NOTE: skipping tape-writable test NOTE: conf info dir /etc/amanda/DailySet1/curinfo does not exist NOTE: it will be created on the next run. NOTE: index dir /etc/amanda/DailySet1/index does not exist NOTE: it will be created on the next run. Server check took 0.880 seconds Amanda Backup Client Hosts Check WARNING: jrcbs01.jrc.local: selfcheck request failed: Connection refused Client check: 1 host checked in 10.020 seconds. 1 problem found. amservice 192.168.1.1 bsdtcp noop [root@jrcbs01 ~]# amservice 192.168.1.5 bsdtcp noop

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