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• Windows server's HDD Spin down daily/nightly - Does it makes sense?

  - by Riccardo

  A Windows Server 2003 R2 has the following hard disk configuration: - 3 internal hard disks attached to a 3Ware unit, configured in Raid 1 + spare unit - 3 external USB backup disks: 2 Verbatim 1TB (Samsung HD103SI) + 1 Western Digital 1TB (WD10EADS) The server runs 365 days per year, h24, however: - at daytime the server/user usage is limited to the internal hard disks - at nighttime there's no user usage, apart from scheduled maintenance tasks, basically the Server will be idle from 7PM to 8AM. apart from nighly backups (few hours). I was wondering if: (a) it makes any sense let Windows manage power savings, allowing disks to spin down accordingly, ** OR** let the disks stay awlays-on, to avoid permature wearing, due to continuous spin up/down (b) leave internal disks always on, and force external disks to power down while idle (this requires third party tools, such as Verbatim's Green button utility) Your thoughts?

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• How can HAProxy improve availibility, or "how can I prevent my site from going down"? [closed]

  - by Joe Hopfgartner

  I am aware of what HAProxy does, but what if my HAproxy goes down? Or what if my DNS servers go down? Yes, dns is less the problem. However dns only solves to an IP and an IP is announced via BGP to be routed over some router. What if that router goes down? Of course if I have complicated application servers that are likely to fail HAProxy can significantly improve uptime. But my application isnt. In fact my application may very well just be delivering a small static html file via HTTP. Basically if any user anywhere types in MYDOMAIN.COM, I want the user to get SOMETHING on the screen other than a timeout or DNS resolution error. How can I do that? The point of entry is difficult. The so called "initial closure mechanism".

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• Is it possible to have tab completion of drop-down lists in web pages in Firefox?

  - by Nick Booker

  Does anyone know of a Firefox plugin that would enable tab-completion (or some other key sequence like Alt-L) of items in drop-down lists in web forms? e.g. ou<TAB>in<TAB>s<TAB> for 'OurCompany - Internal Support' Vimperator's hints mode makes it very ergonomic to focus the drop-down list with a key sequence like f13 but the keyboard interface to the drop-down list still sucks. I very frequently have to pick items from a very long list with very long common prefixes among the entries (e.g. 30-40 starting with OurCompany -), which renders both the built-in keyboard interface and the mouse pretty slow and unergonomic. I basically want readline support for filling webforms!

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• unexplainable packet drops with 5 ethernet NICs and low traffic on Ubuntu

  - by jon

  I'm stuck on problem where my machine started to drops packets with no sign of ANY system load or high interrupt usage after an upgrade to Ubuntu 12.04. My server is a network monitoring sensor, running Ubuntu LTS 12.04, it passively collects packets from 5 interfaces doing network intrusion type stuff. Before the upgrade I managed to collect 200+GB of packets a day while writing them to disk with around 0% packet loss depending on the day with the help of CPU affinity and NIC IRQ to CPU bindings. Now I lose a great deal of packets with none of my applications running and at very low PPS rate which a modern workstation NIC would have no trouble with. Specs: x64 Xeon 4 cores 3.2 Ghz 16 GB RAM NICs: 5 Intel Pro NICs using the e1000 driver (NAPI). [1] eth0 and eth1 are integrated NICs (in the motherboard) There are 2 other PCI-X network cards, each with 2 Ethernet ports. 3 of the interfaces are running at Gigabit Ethernet, the others are not because they're attached to hubs. Specs: [2] http://support.dell.com/support/edocs/systems/pe2850/en/ug/t1390aa.htm uptime 17:36:00 up 1:43, 2 users, load average: 0.00, 0.01, 0.05 # uname -a Linux nms 3.2.0-29-generic #46-Ubuntu SMP Fri Jul 27 17:03:23 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux I also have the CPU governor set to performance mode and irqbalance off. The problem still occurs with them on. # lspci -t -vv -[0000:00]-+-00.0 Intel Corporation E7520 Memory Controller Hub +-02.0-[01-03]--+-00.0-[02]----0e.0 Dell PowerEdge Expandable RAID controller 4 | \-00.2-[03]-- +-04.0-[04]-- +-05.0-[05-07]--+-00.0-[06]----07.0 Intel Corporation 82541GI Gigabit Ethernet Controller | \-00.2-[07]----08.0 Intel Corporation 82541GI Gigabit Ethernet Controller +-06.0-[08-0a]--+-00.0-[09]--+-04.0 Intel Corporation 82546EB Gigabit Ethernet Controller (Copper) | | \-04.1 Intel Corporation 82546EB Gigabit Ethernet Controller (Copper) | \-00.2-[0a]--+-02.0 Digium, Inc. Wildcard TE210P/TE212P dual-span T1/E1/J1 card 3.3V | +-03.0 Intel Corporation 82546EB Gigabit Ethernet Controller (Copper) | \-03.1 Intel Corporation 82546EB Gigabit Ethernet Controller (Copper) +-1d.0 Intel Corporation 82801EB/ER (ICH5/ICH5R) USB UHCI Controller #1 +-1d.1 Intel Corporation 82801EB/ER (ICH5/ICH5R) USB UHCI Controller #2 +-1d.2 Intel Corporation 82801EB/ER (ICH5/ICH5R) USB UHCI Controller #3 +-1d.7 Intel Corporation 82801EB/ER (ICH5/ICH5R) USB2 EHCI Controller +-1e.0-[0b]----0d.0 Advanced Micro Devices [AMD] nee ATI RV100 QY [Radeon 7000/VE] +-1f.0 Intel Corporation 82801EB/ER (ICH5/ICH5R) LPC Interface Bridge \-1f.1 Intel Corporation 82801EB/ER (ICH5/ICH5R) IDE Controller I believe the NIC nor the NIC drivers are dropping the packets because ethtool reports 0 under rx_missed_errors and rx_no_buffer_count for each interface. On the old system, if it couldn't keep up this is where the drops would be. I drop packets on multiple interfaces just about every second, usually in small increments of 2-4. I tried all these sysctl values, I'm currently using the uncommented ones. # cat /etc/sysctl.conf # high net.core.netdev_max_backlog = 3000000 net.core.rmem_max = 16000000 net.core.rmem_default = 8000000 # defaults #net.core.netdev_max_backlog = 1000 #net.core.rmem_max = 131071 #net.core.rmem_default = 163480 # moderate #net.core.netdev_max_backlog = 10000 #net.core.rmem_max = 33554432 #net.core.rmem_default = 33554432 Here's an example of an interface stats report with ethtool. They are all the same, nothing is out of the ordinary ( I think ), so I'm only going to show one: ethtool -S eth2 NIC statistics: rx_packets: 7498 tx_packets: 0 rx_bytes: 2722585 tx_bytes: 0 rx_broadcast: 327 tx_broadcast: 0 rx_multicast: 1504 tx_multicast: 0 rx_errors: 0 tx_errors: 0 tx_dropped: 0 multicast: 1504 collisions: 0 rx_length_errors: 0 rx_over_errors: 0 rx_crc_errors: 0 rx_frame_errors: 0 rx_no_buffer_count: 0 rx_missed_errors: 0 tx_aborted_errors: 0 tx_carrier_errors: 0 tx_fifo_errors: 0 tx_heartbeat_errors: 0 tx_window_errors: 0 tx_abort_late_coll: 0 tx_deferred_ok: 0 tx_single_coll_ok: 0 tx_multi_coll_ok: 0 tx_timeout_count: 0 tx_restart_queue: 0 rx_long_length_errors: 0 rx_short_length_errors: 0 rx_align_errors: 0 tx_tcp_seg_good: 0 tx_tcp_seg_failed: 0 rx_flow_control_xon: 0 rx_flow_control_xoff: 0 tx_flow_control_xon: 0 tx_flow_control_xoff: 0 rx_long_byte_count: 2722585 rx_csum_offload_good: 0 rx_csum_offload_errors: 0 alloc_rx_buff_failed: 0 tx_smbus: 0 rx_smbus: 0 dropped_smbus: 01 # ifconfig eth0 Link encap:Ethernet HWaddr 00:11:43:e0:e2:8c UP BROADCAST RUNNING NOARP PROMISC ALLMULTI MULTICAST MTU:1500 Metric:1 RX packets:373348 errors:16 dropped:95 overruns:0 frame:16 TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:356830572 (356.8 MB) TX bytes:0 (0.0 B) eth1 Link encap:Ethernet HWaddr 00:11:43:e0:e2:8d UP BROADCAST RUNNING NOARP PROMISC ALLMULTI MULTICAST MTU:1500 Metric:1 RX packets:13616 errors:0 dropped:0 overruns:0 frame:0 TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:8690528 (8.6 MB) TX bytes:0 (0.0 B) eth2 Link encap:Ethernet HWaddr 00:04:23:e1:77:6a UP BROADCAST RUNNING NOARP PROMISC ALLMULTI MULTICAST MTU:1500 Metric:1 RX packets:7750 errors:0 dropped:471 overruns:0 frame:0 TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:2780935 (2.7 MB) TX bytes:0 (0.0 B) eth3 Link encap:Ethernet HWaddr 00:04:23:e1:77:6b UP BROADCAST RUNNING NOARP PROMISC ALLMULTI MULTICAST MTU:1500 Metric:1 RX packets:5112 errors:0 dropped:206 overruns:0 frame:0 TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:639472 (639.4 KB) TX bytes:0 (0.0 B) eth4 Link encap:Ethernet HWaddr 00:04:23:b6:35:6c UP BROADCAST RUNNING NOARP PROMISC ALLMULTI MULTICAST MTU:1500 Metric:1 RX packets:961467 errors:0 dropped:935 overruns:0 frame:0 TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:958561305 (958.5 MB) TX bytes:0 (0.0 B) eth5 Link encap:Ethernet HWaddr 00:04:23:b6:35:6d inet addr:192.168.1.6 Bcast:192.168.1.255 Mask:255.255.255.0 UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:4264 errors:0 dropped:16 overruns:0 frame:0 TX packets:699 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:572228 (572.2 KB) TX bytes:124456 (124.4 KB) I tried the defaults, then started to play around with settings. I wasn't using any flow control and I increased the RxDescriptor count to 4096 before the upgrade as well without any problems. # cat /etc/modprobe.d/e1000.conf options e1000 XsumRX=0,0,0,0,0 RxDescriptors=4096,4096,4096,4096,4096 FlowControl=0,0,0,0,0 debug=16 Here's my network configuration file, I turned off checksumming and various offloading mechanisms along with setting CPU affinity with heavy use interfaces getting an entire CPU and light use interfaces sharing a CPU. I used these settings prior to the upgrade without problems. # cat /etc/network/interfaces # The loopback network interface auto lo iface lo inet loopback # The primary network interface auto eth0 iface eth0 inet manual pre-up /sbin/ethtool -G eth0 rx 4096 tx 0 pre-up /sbin/ethtool -K eth0 gro off gso off rx off pre-up /sbin/ethtool -A eth0 rx off autoneg off up ifconfig eth0 0.0.0.0 -arp promisc mtu 1500 allmulti txqueuelen 0 up post-up echo "4" > /proc/irq/48/smp_affinity down ifconfig eth0 down post-down /sbin/ethtool -G eth0 rx 256 tx 256 post-down /sbin/ethtool -K eth0 gro on gso on rx on post-down /sbin/ethtool -A eth0 rx on autoneg on auto eth1 iface eth1 inet manual pre-up /sbin/ethtool -G eth1 rx 4096 tx 0 pre-up /sbin/ethtool -K eth1 gro off gso off rx off pre-up /sbin/ethtool -A eth1 rx off autoneg off up ifconfig eth1 0.0.0.0 -arp promisc mtu 1500 allmulti txqueuelen 0 up post-up echo "4" > /proc/irq/49/smp_affinity down ifconfig eth1 down post-down /sbin/ethtool -G eth1 rx 256 tx 256 post-down /sbin/ethtool -K eth1 gro on gso on rx on post-down /sbin/ethtool -A eth1 rx on autoneg on auto eth2 iface eth2 inet manual pre-up /sbin/ethtool -G eth2 rx 4096 tx 0 pre-up /sbin/ethtool -K eth2 gro off gso off rx off pre-up /sbin/ethtool -A eth2 rx off autoneg off up ifconfig eth2 0.0.0.0 -arp promisc mtu 1500 allmulti txqueuelen 0 up post-up echo "1" > /proc/irq/82/smp_affinity down ifconfig eth2 down post-down /sbin/ethtool -G eth2 rx 256 tx 256 post-down /sbin/ethtool -K eth2 gro on gso on rx on post-down /sbin/ethtool -A eth2 rx on autoneg on auto eth3 iface eth3 inet manual pre-up /sbin/ethtool -G eth3 rx 4096 tx 0 pre-up /sbin/ethtool -K eth3 gro off gso off rx off pre-up /sbin/ethtool -A eth3 rx off autoneg off up ifconfig eth3 0.0.0.0 -arp promisc mtu 1500 allmulti txqueuelen 0 up post-up echo "2" > /proc/irq/83/smp_affinity down ifconfig eth3 down post-down /sbin/ethtool -G eth3 rx 256 tx 256 post-down /sbin/ethtool -K eth3 gro on gso on rx on post-down /sbin/ethtool -A eth3 rx on autoneg on auto eth4 iface eth4 inet manual pre-up /sbin/ethtool -G eth4 rx 4096 tx 0 pre-up /sbin/ethtool -K eth4 gro off gso off rx off pre-up /sbin/ethtool -A eth4 rx off autoneg off up ifconfig eth4 0.0.0.0 -arp promisc mtu 1500 allmulti txqueuelen 0 up post-up echo "4" > /proc/irq/77/smp_affinity down ifconfig eth4 down post-down /sbin/ethtool -G eth4 rx 256 tx 256 post-down /sbin/ethtool -K eth4 gro on gso on rx on post-down /sbin/ethtool -A eth4 rx on autoneg on auto eth5 iface eth5 inet static pre-up /etc/fw.conf address 192.168.1.1 netmask 255.255.255.0 broadcast 192.168.1.255 gateway 192.168.1.1 dns-nameservers 192.168.1.2 192.168.1.3 up ifconfig eth5 up post-up echo "8" > /proc/irq/77/smp_affinity down ifconfig eth5 down Here's a few examples of packet drops, i ran one after another, probabling totaling 3 or 4 seconds. You can see increases in the drops from the 1st and 3rd. This was a non-busy time, very little traffic. # awk '{ print $1,$5 }' /proc/net/dev Inter-| face drop eth3: 225 lo: 0 eth2: 505 eth1: 0 eth5: 17 eth0: 105 eth4: 1034 # awk '{ print $1,$5 }' /proc/net/dev Inter-| face drop eth3: 225 lo: 0 eth2: 507 eth1: 0 eth5: 17 eth0: 105 eth4: 1034 # awk '{ print $1,$5 }' /proc/net/dev Inter-| face drop eth3: 227 lo: 0 eth2: 512 eth1: 0 eth5: 17 eth0: 105 eth4: 1039 I tried the pci=noacpi options. With and without, it's the same. This is what my interrupt stats looked like before the upgrade, after, with ACPI on PCI it showed multiple NICs bound to an interrupt and shared with other devices such as USB drives which I didn't like so I think i'm going to keep it with ACPI off as it's easier to designate sole purpose interrupts. Is there any advantage I would have using the default i.e. ACPI w/ PCI. ? # cat /etc/default/grub | grep CMD_LINE GRUB_CMDLINE_LINUX_DEFAULT="ipv6.disable=1 noacpi pci=noacpi" GRUB_CMDLINE_LINUX="" # cat /proc/interrupts CPU0 CPU1 CPU2 CPU3 0: 45 0 0 16 IO-APIC-edge timer 1: 1 0 0 7936 IO-APIC-edge i8042 2: 0 0 0 0 XT-PIC-XT-PIC cascade 6: 0 0 0 3 IO-APIC-edge floppy 8: 0 0 0 1 IO-APIC-edge rtc0 9: 0 0 0 0 IO-APIC-edge acpi 12: 0 0 0 1809 IO-APIC-edge i8042 14: 1 0 0 4498 IO-APIC-edge ata_piix 15: 0 0 0 0 IO-APIC-edge ata_piix 16: 0 0 0 0 IO-APIC-fasteoi uhci_hcd:usb2 18: 0 0 0 1350 IO-APIC-fasteoi uhci_hcd:usb4, radeon 19: 0 0 0 0 IO-APIC-fasteoi uhci_hcd:usb3 23: 0 0 0 4099 IO-APIC-fasteoi ehci_hcd:usb1 38: 0 0 0 61963 IO-APIC-fasteoi megaraid 48: 0 0 1002319 4 IO-APIC-fasteoi eth0 49: 0 0 38772 3 IO-APIC-fasteoi eth1 77: 0 0 130076 432159 IO-APIC-fasteoi eth4 78: 0 0 0 23917 IO-APIC-fasteoi eth5 82: 1329033 0 0 4 IO-APIC-fasteoi eth2 83: 0 4886525 0 6 IO-APIC-fasteoi eth3 NMI: 5 6 4 5 Non-maskable interrupts LOC: 61409 57076 64257 114764 Local timer interrupts SPU: 0 0 0 0 Spurious interrupts IWI: 0 0 0 0 IRQ work interrupts RES: 17956 25333 13436 14789 Rescheduling interrupts CAL: 22436 607 539 478 Function call interrupts TLB: 1525 1458 4600 4151 TLB shootdowns TRM: 0 0 0 0 Thermal event interrupts THR: 0 0 0 0 Threshold APIC interrupts MCE: 0 0 0 0 Machine check exceptions MCP: 16 16 16 16 Machine check polls ERR: 0 MIS: 0 Here's sample output of vmstat, showing the system. Barebones system right now. root@nms:~# vmstat -S m 1 procs -----------memory---------- ---swap-- -----io---- -system-- ----cpu---- r b swpd free buff cache si so bi bo in cs us sy id wa 0 0 0 14992 192 1029 0 0 56 2 419 29 1 0 99 0 0 0 0 14992 192 1029 0 0 0 0 922 27 0 0 100 0 0 0 0 14991 192 1029 0 0 0 36 763 50 0 0 100 0 0 0 0 14991 192 1029 0 0 0 0 646 35 0 0 100 0 0 0 0 14991 192 1029 0 0 0 0 722 54 0 0 100 0 0 0 0 14991 192 1029 0 0 0 0 793 27 0 0 100 0 ^C Here's dmesg output. I can't figure out why my PCI-X slots are negotiated as PCI. The network cards are all PCI-X with the exception of the integrated NICs that came with the server. In the output below it looks as if eth3 and eth2 negotiated at PCI-X speeds rather than PCI:66Mhz. Wouldn't they all drop to PCI:66Mhz? If your integrated NICs are PCI, as labeled below (eth0,eth1), then wouldn't all devices on your bus speed drop down to that slower bus speed? If not, I still don't know why only one of my NICs ( each has two ethernet ports) is labeled as PCI-X in the output below. Does that mean it is running at PCI-X speeds are is it showing that it's capable? # dmesg | grep e1000 [ 3678.349337] e1000: Intel(R) PRO/1000 Network Driver - version 7.3.21-k8-NAPI [ 3678.349342] e1000: Copyright (c) 1999-2006 Intel Corporation. [ 3678.349394] e1000 0000:06:07.0: PCI->APIC IRQ transform: INT A -> IRQ 48 [ 3678.409725] e1000 0000:06:07.0: Receive Descriptors set to 4096 [ 3678.409730] e1000 0000:06:07.0: Checksum Offload Disabled [ 3678.409734] e1000 0000:06:07.0: Flow Control Disabled [ 3678.586409] e1000 0000:06:07.0: eth0: (PCI:66MHz:32-bit) 00:11:43:e0:e2:8c [ 3678.586419] e1000 0000:06:07.0: eth0: Intel(R) PRO/1000 Network Connection [ 3678.586642] e1000 0000:07:08.0: PCI->APIC IRQ transform: INT A -> IRQ 49 [ 3678.649854] e1000 0000:07:08.0: Receive Descriptors set to 4096 [ 3678.649859] e1000 0000:07:08.0: Checksum Offload Disabled [ 3678.649863] e1000 0000:07:08.0: Flow Control Disabled [ 3678.826436] e1000 0000:07:08.0: eth1: (PCI:66MHz:32-bit) 00:11:43:e0:e2:8d [ 3678.826444] e1000 0000:07:08.0: eth1: Intel(R) PRO/1000 Network Connection [ 3678.826627] e1000 0000:09:04.0: PCI->APIC IRQ transform: INT A -> IRQ 82 [ 3679.093266] e1000 0000:09:04.0: Receive Descriptors set to 4096 [ 3679.093271] e1000 0000:09:04.0: Checksum Offload Disabled [ 3679.093275] e1000 0000:09:04.0: Flow Control Disabled [ 3679.130239] e1000 0000:09:04.0: eth2: (PCI-X:133MHz:64-bit) 00:04:23:e1:77:6a [ 3679.130246] e1000 0000:09:04.0: eth2: Intel(R) PRO/1000 Network Connection [ 3679.130449] e1000 0000:09:04.1: PCI->APIC IRQ transform: INT B -> IRQ 83 [ 3679.397312] e1000 0000:09:04.1: Receive Descriptors set to 4096 [ 3679.397318] e1000 0000:09:04.1: Checksum Offload Disabled [ 3679.397321] e1000 0000:09:04.1: Flow Control Disabled [ 3679.434350] e1000 0000:09:04.1: eth3: (PCI-X:133MHz:64-bit) 00:04:23:e1:77:6b [ 3679.434360] e1000 0000:09:04.1: eth3: Intel(R) PRO/1000 Network Connection [ 3679.434553] e1000 0000:0a:03.0: PCI->APIC IRQ transform: INT A -> IRQ 77 [ 3679.704072] e1000 0000:0a:03.0: Receive Descriptors set to 4096 [ 3679.704077] e1000 0000:0a:03.0: Checksum Offload Disabled [ 3679.704081] e1000 0000:0a:03.0: Flow Control Disabled [ 3679.738364] e1000 0000:0a:03.0: eth4: (PCI:33MHz:64-bit) 00:04:23:b6:35:6c [ 3679.738371] e1000 0000:0a:03.0: eth4: Intel(R) PRO/1000 Network Connection [ 3679.738538] e1000 0000:0a:03.1: PCI->APIC IRQ transform: INT B -> IRQ 78 [ 3680.046060] e1000 0000:0a:03.1: eth5: (PCI:33MHz:64-bit) 00:04:23:b6:35:6d [ 3680.046067] e1000 0000:0a:03.1: eth5: Intel(R) PRO/1000 Network Connection [ 3682.132415] e1000: eth0 NIC Link is Up 100 Mbps Half Duplex, Flow Control: None [ 3682.224423] e1000: eth1 NIC Link is Up 100 Mbps Half Duplex, Flow Control: None [ 3682.316385] e1000: eth2 NIC Link is Up 100 Mbps Half Duplex, Flow Control: None [ 3682.408391] e1000: eth3 NIC Link is Up 1000 Mbps Full Duplex, Flow Control: None [ 3682.500396] e1000: eth4 NIC Link is Up 1000 Mbps Full Duplex, Flow Control: None [ 3682.708401] e1000: eth5 NIC Link is Up 1000 Mbps Full Duplex, Flow Control: RX At first I thought it was the NIC drivers but I'm not so sure. I really have no idea where else to look at the moment. Any help is greatly appreciated as I'm struggling with this. If you need more information just ask. Thanks! [1]http://www.cs.fsu.edu/~baker/devices/lxr/http/source/linux/Documentation/networking/e1000.txt?v=2.6.11.8 [2] http://support.dell.com/support/edocs/systems/pe2850/en/ug/t1390aa.htm

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• How would i down-sample a .wav file then reconstruct it using nyquist? - in matlab [closed]

  - by martin

  This is all done in MatLab 2010 My objective is to show the results of: undersampling, nyquist rate/ oversampling First i need to downsample the .wav file to get an incomplete/ or impartial data stream that i can then reconstuct. Heres the flow chart of what im going to be doing So the flow is analog signal - sampling analog filter - ADC - resample down - resample up - DAC - reconstruction analog filter what needs to be achieved: F= Frequency F(Hz=1/s) E.x. 100Hz = 1000 (Cyc/sec) F(s)= 1/(2f) Example problem: 1000 hz = Highest frequency 1/2(1000hz) = 1/2000 = 5x10(-3) sec/cyc or a sampling rate of 5ms This is my first signal processing project using matlab. what i have so far. % Fs = frequency sampled (44100hz or the sampling frequency of a cd) [test,fs]=wavread('test.wav'); % loads the .wav file left=test(:,1); % Plot of the .wav signal time vs. strength time=(1/44100)*length(left); t=linspace(0,time,length(left)); plot(t,left) xlabel('time (sec)'); ylabel('relative signal strength') **%this is were i would need to sample it at the different frequecys (both above and below and at) nyquist frequency.*I think.*** soundsc(left,fs) % shows the resaultant audio file , which is the same as original ( only at or above nyquist frequency however) Can anyone tell me how to make it better, and how to do the various sampling at different frequencies?

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• How do you keep cool when production system goes down?

  - by Mag20

  This has happened to most of us... You come to work one day. Everything seems normal: the sun is shining, birds are chirping, but you notice a couple of weird things on your way to work like deja vu with cat in matrix. You get into office, there are a lot of phones ringing, but could be that they are just doing a new sales promotion. You settle in, when you notice a dark cloud hovering over you. It takes you a couple of moments, but you recognize the cloud is your boss. Usually he checks on you every morning with his "Soooo Peeeeter, how about those TCP/IP reports?" routine, but today he forgot everything about common manners and rudely invaded your personal space. No "Good Morning", just some drooling, grunts and curses. He reminds you a bit of neanderthal who is trying to get away from cyber tooth tiger, fear and panic all compressed in a tight ball. You try to decipher the new language that he created since yesterday and you start understanding that something bad happened overnight - production system went down. Now, your system is usually used by clients during regular working hours from 9-5, but for whatever reason you didn't get any alerts on your beeper (for people under 30 - beeper was like a mobile phone that could only ring and tell you who beeped you). Need to remember to charge it next time. So it is 8:45am, the system MUST be up at 9am. Every 10 seconds, your boss lets out yet another curse which communicates to you that another customer is having problems getting into the system. Also several account managers are now hovering over your boss trying to make him understand how clients are REALLY REALLY suffering. Everyone is depending on you to get the system up ASAP and at the same time hinder your progress by constantly distracting you. How do you keep cool in a situation like this?

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• Implementing an automatic navigation mesh generation for 2d top down map?

  - by J2V

  I am currently in the middle of implementing an A* pathfinding for enemies. In order to implement the actual A* logic, I need a navigation mesh for my map. I am working on a 2D top down rpg map. The world is static, meaning there is no requirement for dynamic runtime mesh generation. My world objects are pixel based, not tile based and have associated data with them such as scale, rotation, origin etc. I will obviously need some vertex data being generated from my world objects, maybe create a polygon generation from color data? I could create a colormap with objects for my whole map, but I have no idea how to begin creating nav mesh polygons. How would an actual navigation mesh generation look like with this kind of available information? Can anyone maybe point to some great resources? I have looked into some 3D nav mesh tools, but they seem kind of overly complex for my situation and also have a lot of their req data available from models. Thanks a lot in advance! I have been trying to get my head around it for some time now.

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• Can't mount USB devices, shut down etc. as a user

  - by Alok

  I tried gnome3 and gnome3-staging ppas to test running Gnome 3.8. After a while I decided that Gnome 3.8 wasn't for me, so I did a ppa-purge of both the ppas. As described in gnome3-staging ppa page, I also did: $ sudo apt-get purge libpam-systemd $ sudo apt-get install libpam-xdg-support The trouble is, I can't mount my external USB device anymore. When I try to mount it as a user, it fails: $ udisks --mount /dev/sdc1 Mount failed: Not Authorized I am logged in an XFCE session, but the same thing happens in a fallback Gnome session, or from a Unity session. Also, in XFCE, "suspend" and "shut down" menus are grayed out. I can't also open synaptic package manager from XFCE menus (sudo synaptic works). After a lot of searching, it seems like it is a policykit issue. I see the following in my ~/.xsession-errors: (polkit-gnome-authentication-agent-1:5805): polkit-gnome-1-WARNING **: Unable to determine the session we are in: No session for pid 5805 PID 5805 doesn't exist. If I try to start polkit-dnome-authentication-agent-1 from an xterm, I get the same error (different PID): $ /usr/lib/policykit-1-gnome/polkit-gnome-authentication-agent-1 ... (polkit-gnome-authentication-agent-1:15971): polkit-gnome-1-WARNING **: Unable to determine the session we are in: No session for pid 15971 (the ... lines are warnings from GTK about missing css files etc.). polkitd is running: $ pidof polkitd 1495 Is there something I am missing?

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• How do I make my character slide down high-angled slopes?

  - by keinabel

  I am currently working on my character's movement in Unity3D. I managed to make him move relatively to the mouse cursor. I set a slope limit of 45°, which does not allow the character to walk up the mountains with higher degrees. But he can still jump them up. How do I manage to make him slide down again when he jumped at places with too high slope? Thanks in advance. edit: Code snippet of my basic movement. using UnityEngine; using System.Collections; public class BasicMovement : MonoBehaviour { private float speed; private float jumpSpeed; private float gravity; private float slopeLimit; private Vector3 moveDirection = Vector3.zero; void Start() { PlayerSettings settings = GetComponent<PlayerSettings>(); speed = settings.GetSpeed(); jumpSpeed = settings.GetJumpSpeed(); gravity = settings.GetGravity(); slopeLimit = settings.GetSlopeLimit(); } void Update() { CharacterController controller = GetComponent<CharacterController>(); controller.slopeLimit = slopeLimit; if (controller.isGrounded) { moveDirection = new Vector3(Input.GetAxis("Horizontal"), 0, Input.GetAxis("Vertical")); moveDirection = transform.TransformDirection(moveDirection); moveDirection *= speed; if (Input.GetButton("Jump")) { moveDirection.y = jumpSpeed; } } moveDirection.y -= gravity * Time.deltaTime; controller.Move(moveDirection * Time.deltaTime); } }

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• Why does the player fall down when in between platforms? Tile based platformer

  - by inzombiak

  I've been working on a 2D platformer and have gotten the collision working, except for one tiny problem. My games a tile based platformer and whenever the player is in between two tiles, he falls down. Here is my code, it's fire off using an ENTER_FRAME event. It's only for collision from the bottom for now. var i:int; var j:int; var platform:Platform; var playerX:int = player.x/20; var playerY:int = player.y/20; var xLoopStart:int = (player.x - player.width)/20; var yLoopStart:int = (player.y - player.height)/20; var xLoopEnd:int = (player.x + player.width)/20; var yLoopEnd:int = (player.y + player.height)/20; var vy:Number = player.vy/20; var hitDirection:String; for(i = yLoopStart; i <= yLoopEnd; i++) { for(j = xLoopStart; j <= xLoopStart; j++) { if(platforms[i*36 + j] != null && platforms[i*36 + j] != 0) { platform = platforms[i*36 + j]; if(player.hitTestObject(platform) && i >= playerY) { hitDirection = "bottom"; } } } } This isn't the final version, going to replace hitTest with something more reliable , but this is an interesting problem and I'd like to know whats happening. Is my code just slow? Would firing off the code with a TIMER event fix it? Any information would be great.

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• Is there an alternative to Windows-Down to minimize?

  - by RoboShop

  I remember with Windows XP, minimize used to be like alt m - n or something. In Windows 7, it is Windows - Down. The problem with that though is that you have to use both hands (the Window button is too far away from the directional buttons), which is kind of annoying because generally, one of my hands is on the mouse. Is there any other keyboard to minimize a window besides Windows - Down in Windows 7?

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• How to flip video feed that's presented upside down?

  - by Zuul

  Skype an other applications running under windows 7 Ultimate are presenting the video captured from the laptop built-in webcam upside down. I've tried many solution that I was able to find regarding issues like this, but to no avail. Some of the most relevant are discussed here: From Skype Support Network, the thread why is my video image of myself upside-down??? From ASUSTek Forums, the thread Built-in camera upside down Both present several potential solutions to this issue, but I've been unable to fix it for the laptop ASUS U6S. What I've already tried: Changing Drivers The driver that works must be the one from Windows, all others available from ASUS drivers either don't install or install but the webcam doesn't provide any video feed. This disallows all options that concern using an older driver or editing the .inf file as to manually adjust the settings. ASUS does not provide drivers for Windows 7, so I've used drivers from Windows Vista 32 Bit. Using the application manycam This application actually solves the issue (temporarily), but creates new ones: If I use the application to flip the video feed, Skype video call cease to work. This application doesn't save the settings, at least I wasn't able to find any way to save the settings I've used to flip the video feed. A computer restart brings all back to how it was, video feed upside down and if the application is still installed, Skype continues to fail on video calls. Regedit I've searched thru Windows Registry Editor as to find any reference to the webcam settings, hopping to find a key with the Flip parameter, since it's up to the driver to flip the image (by what I could ascertain from this problem). Couldn't find any reference to such settings, either they actually don't exist within the Windows Registry or they use some weird name that I could think off. System Configuration I was able to access the webcam system settings from the Windows Device Manager, but the tab that actually has the Image Rotation setting is always disabled. The same goes for the settings available from the Skype webcam options (that essentially is presenting the same settings as Windows Device Manager, just within a custom Skype pop-up). Question: How can I flip the video feed from the laptop's built-in webcam, as to properly see and broadcast the video?

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• Slow down individual connections passing through a Linux router?

  - by davr

  We have a Linux server acting as a router/firewall for our office. Occasionally someone will upload a large file that takes up all our bandwidth. I don't want to implement any complex rules or traffic shaping, but I'm wondering if there is a way to slow down a single connection on the spot? I found tcpnice, but it doesn't slow down the transfers in my testing.

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• Computer shows error message when being shut down. What does it mean?

  - by Xavierjazz

  My OS is Windows XP SP3. This message sometimes comes up when I am shutting the computer down: The instruction at 0x00000000 referenced memory at 0x00000000. The memory could not be read. The computer still shuts down. I cannot find a reference to this happening on shutdown, it only seems to be connected to programs that I don't have. I have the whole Word 2003 package. Any direction appreciated.

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• Why does my computer restart immediately after I shut it down?

  - by Youri

  After I shut down my computer it automatically starts up again. I've tried re-installing Windows 7 64-bit, resetting my BIOS, installing the newest drivers and also changing the boot and recovery settings. The motherboard I have is a MSI P67A-GD65 (B3), and the processor is a Intel Core i7-2600K. How can I shut down my computer and have it stay off? Also, what is causing it to immediately boot back up?

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• Play Your Position Until the Play Breaks Down&hellip;then Do Whatever it Takes.

  - by AjarnMark

  If I didn’t know better, I would think that K. Brian Kelley (blog | twitter) has been listening in on conversations with my boss. In his recent blog post Successful Teams: Knowing When to Step Out of Your Role, Brian describes quite clearly a philosophy that my boss has been trying to get across to everyone in the department.  We have been using sports analogies, like how important it is to play your position, until the play breaks down (such as a fumble) and then do whatever it takes it to cover each other / recover the ball / win.  While we like having very skilled people who could do a lot of different tasks, it is important that you first do your assigned tasks, and only once those are complete, or failure of the larger mission is probable, do you consider walking away from them to help someone else with their responsibilities. The thing that you cannot afford, especially on a lean team, is the really nice guy who is always trying to help out other people, but in doing so, is never quite getting his own responsibilities taken care of.  Yes, if the Running Back drops the football, you want any member of the team in the vicinity to jump on it, whether that is the leading blocker or the Quarterback.  But until the fumble happens, you want the leading blocker to focus on doing his job, and block for the Running Back.  If the blocker is doing any other job than his primary responsibility, you’re probably going to lose. This sounds logical enough, but it is really easy to go astray with the best of intentions.  This is especially true on a small, tight-knit team, where it is really easy to get sucked into someone else’s task or problem, doubly so if you think you can do it better or faster than them.  Now you are really setting yourself up for failure.  The right thing is to let the other person do the job, even if it seems less efficient in the short-run, so that you can focus on the tasks which require your expertise.  Don’t break formation…don’t abandon your assignment, until it is clear that mission failure is imminent, and even then, as Brian writes, it should be with the agreement of the mission leader. Thanks, Brian, for putting it so well.  This has been distributed throughout our department.

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• Zelda-style top-down RPG. How to store tile and collision data?

  - by Delerat

  I'm looking to build a Zelda: LTTP style top-down RPG. I've read a lot on the subject and am currently going back and forth on a few solutions. I'm using C#, MonoGame, and Tiled. For my tile maps, these are the choices I can see in front of me: Store each tile as its own array. Each one having 3-4 layers, texture/animation, depth, flags, and maybe collision(depending on how I do it). I've read warning about memory issues going this route, and my biggest map will probably be 160x120 tiles. My average map however will be about 40x30. The number of tiles might cut in half if I decide to double my tile size, which is currently 16x16. This is the most appealing approach for me, as I feel like I would know how to save maps, make changes, and separate it into chunks for collision checks. Store the static parts of my tile map in multiple arrays acting as the different layers. Then I would just use entities for anything that wasn't static. All of the other tile data such as collisions, depth, etc., would be stored in their own layers as well I guess? This way just seems messy to me though. Regardless of which one I choose, I'm also unsure how to plan all of that other tile data. I could write a bunch of code that would know which integer represents what tile and it's data, but if I changed a tileset in Tiled and exported it again, all of those integers could potentially change and I'd have to adjust a whole bunch of code. My other issue is about how I could do collision. I want to at least support angled collision that slides you around the corners of objects like LTTP does, if not more oddball shapes as well. So do I: Store collision as a flag for binary collision. Could I get this to support angles? Would it be fine to store collision as an integer and have each number represent a certain angle of collision? Store a list of rectangles or other shapes and do collision that way? Sorry for the large two-part(three-part?) question. I felt like these needed to be asked together as I believe each choice influences the other.

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• List of common ways those could shut down server unexpectedly ?

  - by SpawnCxy

  After running a bash fork bomb which made my webserver down, I think I should be more careful even not under root.I thought it would be totally fine while I'm not under root.So I ignored the warning and ran the bash fork bomb which is :() { :|:& }; : .(Please don't run it if u don't understand this code cuz it will make you system down).And I think I need a list of common ways those could cause a sever shutting down unexpectly even not under root. Any suggestion would be appreciated. Regards `

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• How can I make Access combo boxes unfurl on arrow key down?

  - by Matt Parker

  With combo box controls, I'm used to being able tab to them, click the down arrow key to open up the options, and then use the up and down arrow keys to navigate those options. In an Access form I've designed, pressing down while a combo box is active moves to the next control. I already have tab for that, so how can I get the down arrow to behave as I expect? These combo boxes are the only thing between me and a mouse-free form, which I consider essential for data entry. Thanks in advance for your help!

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• Is there a way to fix the width of drop down list?

  - by Harry Pham

  Here is what I got: <select id="box1"> <option>ABCDEFG</option> </select> <select id="box2"> <option>ABCDEFGHIJKLMNO</option> </select> I have 2 different Drop Down lists. Since the width of a drop down list depends on the width of the longest text in the option, I end up with 2 drop down lists with 2 different widths. This makes my webpage look goofy. What I want is to set it so that both of my drop down lists will have the same width (I'd prefer the width to be very long, so that even the longest item won't be truncated).

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• jQuery: Scroll down page a set increment (in pixels) on click?

  - by bcWeb

  I'm trying to make a page scroll down 150px from the current position when an element is clicked. So lets say you're roughly halfway scrolled down a page. You click this link, and it will slide you down an additional 150 pixels. Is this possible with jQuery? I've been looking at scrollTop and the scrollTo plugin, but I can't seem to connect the dots.

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• How can i return the value of disabled drop-down field after submit?

  - by ninja

  Hi, I have a drop down field that if any items of it selected,it would be disabled,after that i submit the form,but then (after submitting) the drop down field dosent have any value, I want to have a value after submit but my drop down field is empty. Thanks for any help, (sorry for my English)

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• How do I call an upside down jQuery.slideDown()?

  - by Mark Rogers

  In the web app I'm working on I want to do a little slide up notification, like on twitter or your desktop. jQuery's .slideDown does exactly what I want, but it's upside down. The .slideUp doesn't execute an upside down version of slideDown. Instead it hides stuff, like after your cleaning up an old message you've displayed with slideDown. So what's the simplest code to do an upside down slideDown() in jQuery?

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• How does one skip "Windows did not shut down successfully" in Win7-64?

  - by XenonofArcticus

  Migrating an app from an expensive and unreliable dedicated embedded x86 box running WinXP-embedded to COTS hardware (Dell E6410 laptop) running normal Win7-64. At this time, it's not feasible to deploy using Windows 7 embedded. The problem is, that the system is still sort of "embedded". The power could shut off at virtually any time without prior warning. We've stripped the OS down and removed the battery capability so that it will power down as desired. The app never writes to the disk, so it's not like we're going to corrupt anything terribly. The system is essentially idle after our app is up and running (with the exception of some computation, graphics, and TCP/IP and serial communications) so the OS enters a pretty stable state rather quickly. After a power-loss however, it rightly complains that Windows did not shut down successfully and presents the user with the Windows Error Recovery text screen. If left alone, it does eventually move on booting just fine, but we'd like to skip that step if possible. WinXP-embedded is designed to do this automatically, so I know it's possible. I've looked at the Kernel Switches but I didn't see anything documented for "Skip Windows Error Recovery". I've also read extensively on the startup process: http://homepage.ntlworld.com./jonathan.deboynepollard/FGA/windows-nt-6-boot-process.html I know I can disable the auto chkdsk in the registry, but that's not the same thing either. So, how do I streamline the boot process to not hassle the user about a situation that will be the regular normal situation?

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• Does migrating 2 domain controllers between 2 datacentre requires both virtual machines to be shut down at the same time?

  - by Imagineer

  I was attempting to migrate 2 virtual machines that are domain controllers between 2 datacentres running ESX 3.5 and ESX 4.1. I was advised to shut down both domain controller at the same time during the migration process. This is to avoid USN Rollback and other replication issues. The following are the steps that I was planning to perform: 1. Shutdown both DC. 2. Copy both VMs files across to new datacentre using Veeam FastSCP (connection to both vCentre through IP address instead of hostname) 3. Power them up at new datacentre. 4. Configure Network interface/DNS/DHCP for both DCs in new datacentre I have tried to use Veeam FastSCP rather than VMware Standalone Converter is because its copying rather than converting. Someone also suggested that I use backup and restore app like Veeam backup and replication software. Sounds like a simple job, but after shutting down both DCs, the transfer rate using FastSCP is so slow registering only 1KB/s as oppose to the normal 1MB/s (or more). When that attempt to transfer failed, I tried to cold clone both DCs resulted in the both ESX hosts get disconnected. I have tried troubleshooting by referring to this - VMware KB - Diagnosing an ESX Server that is Disconnected or Not Responding in VirtualCenter It seems that the DNS being down is the caused of all unusual occurrence. The moment I powered up the DCs via VMware console command, the ESX host were able to connect to the vCentre again. How can I avoid such a pitfall again? Am I doing it correctly? Any help would be greatly appreciated! Thank you.

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