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  • How is it possible for SSD's drives to have such a good latency?

    - by tigrou
    First time i read some information about SSD's, i was surprised to learn they internally use NAND flash chips. This kind of memory is generally slow (low bandwidth) and have high latency while SSD's are just the opposite. But here is how it works : SSD drives increase their bandwidth by using several NAND flash chips in parallel. In other words, they do some data striping (aka RAID0) across several chips (done by the controller). What i don't understand is how SSD's drives have such a low latency, whereas they are using NAND chips? (or at least lot better than what a typical single NAND chip would do) EDIT: I think under-estimate NAND chip capabilities. USB drives, while powered by NAND's are mostly limited by USB protocol (which have a pretty high latency) and the USB controller. That explain their poor performance in some cases.

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  • How SSD's drives reduce their latency?

    - by tigrou
    First time i read some information about SSD's, i was surprised to learn they internally use NAND flash chips. This kind of memory is generally slow (low bandwidth) and have high latency while SSD's are just the opposite. But here is how it works : SSD drives increase their bandwidth by using several NAND flash chips in parallel. In other words, they do some data striping (aka RAID0) across several chips (done by the controller). What i don't understand is how SSD's drives managed to reduce latency? (or at least lot better than what a single NAND chip without any controller can do)

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  • AMD 24 core server memory bandwidth

    - by ntherning
    I need some help to determine whether the memory bandwidth I'm seeing under Linux on my server is normal or not. Here's the server spec: HP ProLiant DL165 G7 2x AMD Opteron 6164 HE 12-Core 40 GB RAM (10 x 4GB DDR1333) Debian 6.0 Using mbw on this server I get the following numbers: foo1:~# mbw -n 3 1024 Long uses 8 bytes. Allocating 2*134217728 elements = 2147483648 bytes of memory. Using 262144 bytes as blocks for memcpy block copy test. Getting down to business... Doing 3 runs per test. 0 Method: MEMCPY Elapsed: 0.58047 MiB: 1024.00000 Copy: 1764.082 MiB/s 1 Method: MEMCPY Elapsed: 0.58012 MiB: 1024.00000 Copy: 1765.152 MiB/s 2 Method: MEMCPY Elapsed: 0.58010 MiB: 1024.00000 Copy: 1765.201 MiB/s AVG Method: MEMCPY Elapsed: 0.58023 MiB: 1024.00000 Copy: 1764.811 MiB/s 0 Method: DUMB Elapsed: 0.36174 MiB: 1024.00000 Copy: 2830.778 MiB/s 1 Method: DUMB Elapsed: 0.35869 MiB: 1024.00000 Copy: 2854.817 MiB/s 2 Method: DUMB Elapsed: 0.35848 MiB: 1024.00000 Copy: 2856.481 MiB/s AVG Method: DUMB Elapsed: 0.35964 MiB: 1024.00000 Copy: 2847.310 MiB/s 0 Method: MCBLOCK Elapsed: 0.23546 MiB: 1024.00000 Copy: 4348.860 MiB/s 1 Method: MCBLOCK Elapsed: 0.23544 MiB: 1024.00000 Copy: 4349.230 MiB/s 2 Method: MCBLOCK Elapsed: 0.23544 MiB: 1024.00000 Copy: 4349.359 MiB/s AVG Method: MCBLOCK Elapsed: 0.23545 MiB: 1024.00000 Copy: 4349.149 MiB/s On one of my other servers (based on Intel Xeon E3-1270): foo2:~# mbw -n 3 1024 Long uses 8 bytes. Allocating 2*134217728 elements = 2147483648 bytes of memory. Using 262144 bytes as blocks for memcpy block copy test. Getting down to business... Doing 3 runs per test. 0 Method: MEMCPY Elapsed: 0.18960 MiB: 1024.00000 Copy: 5400.901 MiB/s 1 Method: MEMCPY Elapsed: 0.18922 MiB: 1024.00000 Copy: 5411.690 MiB/s 2 Method: MEMCPY Elapsed: 0.18944 MiB: 1024.00000 Copy: 5405.491 MiB/s AVG Method: MEMCPY Elapsed: 0.18942 MiB: 1024.00000 Copy: 5406.024 MiB/s 0 Method: DUMB Elapsed: 0.14838 MiB: 1024.00000 Copy: 6901.200 MiB/s 1 Method: DUMB Elapsed: 0.14818 MiB: 1024.00000 Copy: 6910.561 MiB/s 2 Method: DUMB Elapsed: 0.14820 MiB: 1024.00000 Copy: 6909.628 MiB/s AVG Method: DUMB Elapsed: 0.14825 MiB: 1024.00000 Copy: 6907.127 MiB/s 0 Method: MCBLOCK Elapsed: 0.04362 MiB: 1024.00000 Copy: 23477.623 MiB/s 1 Method: MCBLOCK Elapsed: 0.04262 MiB: 1024.00000 Copy: 24025.151 MiB/s 2 Method: MCBLOCK Elapsed: 0.04258 MiB: 1024.00000 Copy: 24048.849 MiB/s AVG Method: MCBLOCK Elapsed: 0.04294 MiB: 1024.00000 Copy: 23847.599 MiB/s For reference here's what I get on my Intel based laptop: laptop:~$ mbw -n 3 1024 Long uses 8 bytes. Allocating 2*134217728 elements = 2147483648 bytes of memory. Using 262144 bytes as blocks for memcpy block copy test. Getting down to business... Doing 3 runs per test. 0 Method: MEMCPY Elapsed: 0.40566 MiB: 1024.00000 Copy: 2524.269 MiB/s 1 Method: MEMCPY Elapsed: 0.38458 MiB: 1024.00000 Copy: 2662.638 MiB/s 2 Method: MEMCPY Elapsed: 0.38876 MiB: 1024.00000 Copy: 2634.043 MiB/s AVG Method: MEMCPY Elapsed: 0.39300 MiB: 1024.00000 Copy: 2605.600 MiB/s 0 Method: DUMB Elapsed: 0.30707 MiB: 1024.00000 Copy: 3334.745 MiB/s 1 Method: DUMB Elapsed: 0.30425 MiB: 1024.00000 Copy: 3365.653 MiB/s 2 Method: DUMB Elapsed: 0.30342 MiB: 1024.00000 Copy: 3374.849 MiB/s AVG Method: DUMB Elapsed: 0.30491 MiB: 1024.00000 Copy: 3358.328 MiB/s 0 Method: MCBLOCK Elapsed: 0.07875 MiB: 1024.00000 Copy: 13003.670 MiB/s 1 Method: MCBLOCK Elapsed: 0.08374 MiB: 1024.00000 Copy: 12228.034 MiB/s 2 Method: MCBLOCK Elapsed: 0.07635 MiB: 1024.00000 Copy: 13411.216 MiB/s AVG Method: MCBLOCK Elapsed: 0.07961 MiB: 1024.00000 Copy: 12862.006 MiB/s So according to mbw my laptop is 3 times faster than the server!!! Please help me explain this. I've also tried to mount a ram disk and use dd to benchmark it and I get similar differences so I don't think mbw is to blame. I've checked the BIOS settings and the memory seem to be running at full speed. According to the hosting company the modules are all OK. Could this have something to do with NUMA? It seems like Node Interleaving is disabled on this server. Will enabling it (thus turning off NUMA) make a difference? foo1:~# numactl --hardware available: 4 nodes (0-3) node 0 cpus: 0 1 2 3 4 5 node 0 size: 8190 MB node 0 free: 7898 MB node 1 cpus: 6 7 8 9 10 11 node 1 size: 12288 MB node 1 free: 12073 MB node 2 cpus: 18 19 20 21 22 23 node 2 size: 12288 MB node 2 free: 12034 MB node 3 cpus: 12 13 14 15 16 17 node 3 size: 8192 MB node 3 free: 8032 MB node distances: node 0 1 2 3 0: 10 20 20 20 1: 20 10 20 20 2: 20 20 10 20 3: 20 20 20 10

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  • Can I switch input methods while Caps Lock is being held down on Windows?

    - by Syzygy
    On my Linux computer, my keyboard switches from English to Serbian when I hold the Caps Lock key. For example, to write c all I have to do is hold Caps Lock, and press the key where c is on the Serbian keyboard (in this case, they key is ; on the English keyboard). When I release Caps Lock, the keyboard "switches back" to English, so that if I press ; I get ; as desired. Super useful. Please note that I know how to change the keyboard layout. I want to use Caps Lock as a modifier key to change the language only while being held down! Is there a way to replicate this behavior on Windows 7 or Windows 8?

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  • big speed difference on a network link with and without VPN tunnel

    - by xirtyllo
    Scenario: We have a network link between two offices. The link is provided by a third party company through a VLAN on their network, but to us it is totally transparent -as if we had a simple ethernet cable going from one location to the other-. We have one router at each side of the link, with 3 VPN tunnels in between the two. The test: When I test the speed of the network link with the routers in place, with one laptop directly connected to the router on each side, I consistently get ~30/35Mbps. But if I take out the routers and I test the link connecting the laptops directly to the ethernet cable at each side, I consistently get ~85/88Mbps. It's quite a big performance hit, and I would tend to think that the VPN tunnels are responsible for the slow down. Is it normal that this configuration (two routers with three VPN tunnels between them) takes away so much bandwidth? More info: The encryption algorithm used for the VPN tunnels is AES128. The routers model is Zyxel USG200 and Zyxel USG1000, and their CPU, memory, and storage use is well within normal limits. The nominal bandwidth of the network link is 100Mbps. The network link in question is supplied by a third party company (the building in between our two offices). Basically it passes through their network as a VLAN, but the VLAN is completely transparent to us (e.g. no configuration required on our side, just like one single cable from end to end). Unfortunately (or maybe fortunately) I cannot directly test different routers configurations as I'm not the person in charge of it.

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  • Pygame program that can get keyboard input with caps

    - by None
    I have a Pygame program that needs text input. The way it does this is to get keyboard input and when a key is pressed it renders that key so it is added to the screen. Essentially it acts like a text field. The problem is, when you hold shift it doesn't do anything. I relize this is because the program ignores shift input and instead writes the text if it's number is under 128. I have thought of setting a variable when shift is pressed then capitalizing if it was true, but string capitalization only woks on letters, not things like numbers or semicolons. Is there maybe a number I can add to the ascii number typed to modify it if shift is pressed, or something else?

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  • Server suffering serious speed drop

    - by Tar
    As you can see from the picture http://i.imgur.com/UpDZh.png), my server is suffering a serious drop in speed. This is intermittent and has been happening for the past 3 or 4 hours. The server has 1gbps uplink so I can't figure out why it's happening. Checking bandwidth monitoring tools like bwm-ng and dstat show normal speeds of like 150kb/s outbound traffic. Just now I was completely disconnected from SSH.

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  • Limiting interface bandwidth with tc under Linux

    - by Matt
    I have a linux router which has a 10GBe interface on the outside and bonded Gigabit ethernet interfaces on the inside. We have currently budget for 2GBit/s. If we exceed that rate by more than 5% average for a month then we'll be charged for the whole 10Gbit/s capacity. Quite a step up in dollar terms. So, I want to limit this to 2GBit/s on 10GBe interface. TBF filter might be ideal, but this comment is of concern. On all platforms except for Alpha, it is able to shape up to 1mbit/s of normal traffic with ideal minimal burstiness, sending out data exactly at the configured rates. Should I be using TBF or some other filter to apply this rate to the interface and how would I do it. I don't understand the example given here: Traffic Control HOWTO In particular "Example 9. Creating a 256kbit/s TBF" tc qdisc add dev eth0 handle 1:0 root dsmark indices 1 default_index 0 tc qdisc add dev eth0 handle 2:0 parent 1:0 tbf burst 20480 limit 20480 mtu 1514 rate 32000bps How is the 256K bit/s rate calculated? In this example, 32000bps = 32k bytes per second. Since tc uses bps = bytes per second. I guess burst and limit come into play but how would you go about choosing sensible numbers to reach the desired rate? This is not a mistake. I tested this and it gave a rate close to 256K but not exactly that.

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  • How much bandwidth does my server require?

    - by Jagira
    Hello, I have blog + website hosted on Godaddy server. I get somewhere around 50k hits a day. I was thinking of hosting it on my own. I want to know whether a 2mbps connection is sufficient or not? Somebody with self-hosting experience please guide...

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  • Wireless mouse keeps freezing when using whole network bandwidth

    - by Ümit AKKAYA
    Hi i have wireless mouse and keyboard connected to pc with USB receiver. When i downloading something without limiting download speed, mouse and keyboard keep freezing randomly. Mouse : Microsoft Wireless Mouse 5000 Keyboard : Microsoft keyboard 3000 v2 Chipset : Intel HM65 Processor : Intel Core i7 2670QM @ 2200MHz Physical Memory : 8192MB (2 x 4096 DDR3-SDRAM) OS : Win 7 x64 Note : The solution described in http://superuser.com/a/309622/157168 not helped.

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  • ntop to analyse bandwidth usage on multiple ASA 5505

    - by dunxd
    I have set up a netflow server at our data centre, which is connected via VPN to ~40 remote offices using Cisco ASA 5505. The aim is to analyse usage data and find out exactly how the remote connections are being used. I followed through http://techowto.files.wordpress.com/2008/09/ntop-guide.pdf to set up ntop and https://supportforums.cisco.com/docs/DOC-6114 to set up the ASAs. I can see from the Plugin Netflow Statistics page that netflow packets from my ASAs are being received - the counter is increasing. However, I am not seeing any breakdown on the Global Traffic Statistic page after switching to the Netflow interface. I'm just seeing a pie chart showing 100% traffic for eth0. The interfaces and documentation are a little hard to follow so I am not sure I have got things configured correctly. When setting up my NetFlow-device.2 I can specify Virtual NetFlow Interface Network Address - the web UI says This value is in the form of a network address and mask on the network where the actual NetFlow probe is located. is this a Network address (e.g. 192.168.0.0/24) or an actual host IP address (192.167.0.1/24)? If that should be a network address, is this the network in which one of my ASAs is or the network in which my ntop server is? If a host IP address, is this the IP address used by eth0 on my ntop server, the IP address of an ASA, or something else? Do I need a separate virtual interface for each ASA I am collecting netflow data from? Any guidance would be greatly welcome.

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  • Monitoring bandwidth/latency/jitter between 2 sites?

    - by TheCleaner
    I have 2 sites connected via an MPLS network and I'd like to do the following: setup a host on each end that can "talk" back and forth between each other and somehow report/log what kind of throughput, jitter, latency, etc. they are experiencing between each other in 5 minute intervals. Something similar to Qcheck but that can be automated. Bottom line is I'm trying to determine if the WAN network is "stable" throughout the day or if something is wrong. We have video conferences between these sites and even at 1024kbps calls we are experiencing delays and jitter. I'm hoping to exonerate the network with some testing.

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  • How to monitor streaming servers

    - by pcdinh
    Hi all, I have had a bunch of Linux based streaming servers that employed lighttpd web server to provide video streaming via port 80. Recently, our service is very slow. Therefore, I would like to ask if there is a good software package that helps us monitor and record our bandwidth usage, lighttpd established connections, TCP sync connections, disk I/O ... over time. Any suggestions? Regards, Dinh

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  • controlling the bandwidth using tc

    - by Supratik
    Hi I have two NIC etho is connected to the internet and eth1 is connected to the LAN. I want to restrict the download limit using iptables and linux tc. So I wrote a test script to verify if it is working. My iptables configuration is as below. iptables -t mangle -N INBOUND iptables -t mangle -I PREROUTING -i eth0 -j INBOUND iptables -t mangle -A INBOUND -j MARK --set-mark 60 My ingress configuration is as below. tc qdisc add dev eth0 handle 1: ingress tc filter add dev eth0 parent 1: protocol ip prio 1 handle 60 fw police rate 100kbit burst 20kbit drop flowid :1 Can you please tell me what I am missing here ?

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  • How do I get to the bottom of network latency and bandwidth issues

    - by three_cups_of_java
    I recently moved two blocks south. That move moved me from Comcast to Broadstripe (high-speed internet cable providers). Comcast was pretty good. Broadstripe sucks. I called them on the phone, and they basically brushed me off (politely). I want to come to them with some numbers, so I can say more than just "it's really slow". I still have access to my old Comcast service, so I can run the tests using both providers. Here's what I'm seeing with my new Broadstripe service: 1) When I browse to most sites, there is a long delay (5-10 seconds) before the page starts loading in my browser 2) The speed test tell me I have 12 megs down (bullshit) 3) I have a server at my office. I just downloaded some files (using scp on the command line). It said I'm getting 3.5 KB/s I'm an experienced programmer and spend most of my days on the command line and in vim. Networking, however is not a strong point. I've played around with traceroute, but I'm not sure if that's the right tool to use. I have access to servers all over the country (I would just use Amazon EC2 to set up a test server), and I prefer to use Ubuntu for my testing. How can I come up with some hard numbers to show Broadstripe how crappy their service is?

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  • How do I assess the capacity of my link for Active Directory needs?

    - by adon
    I'm working for a company that has a head office and some remote sites. We have an Active Directory server in the head office and we now want all of the users in the remote sites to join and work on the domain at the head office. I want to assess our bandwidth to see if we have enough to carry all the traffic between offices smoothly. What can I do or which tool can I use for the assessment and statistics?

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  • reduce bandwidth streaming mp3s php...

    - by Scarface
    Hey guys, quick question for any experts out there. I am allowing users to upload and post mp3s so other users can listen to/stream. I was wondering if anyone had any tips for reducing bandwidth, or any tips or methods for streaming mp3s. I currently just reference the location of the file with my flash mp3 player after the file has been uploaded. I would ask about images as well, but I am pretty sure they can be compressed using gzip or mod_deflate

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  • How can I limit user bandwidth usage?

    - by Scarface
    Ok, I have a site, and it serves all images and mp3s through a php script and can be controlled and limited, but I am now worried about overall bandwidth of my site. For example, what if someone just sends a million requests to one of my pages? Does anyone have any suggestions into server methods used to prevent this? Should I use mod_cband http://www.howtoforge.com/mod_cband_apache2_bandwidth_quota_throttling_p2?

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