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• Oracle's Cloud Strategie nach der OOW 2012

  - by Manuel Hossfeld

  Auf der diesjährigen Oracle Open World war „die Cloud“ nicht nur ein vielbenutztes Buzzword, sondern auch Anlass für einige interessante Ankündigungen. Wer keine Zeit oder Muße hatte, sich die entsprechenden Keynotes von Larry Ellison und Thomas Kurian anzuhören, erfährt in diesem Artikel die wesentlichen Änderungen. Die erste Neuerung: Oracle wird in Zukunft alle drei „Sorten“ bzw. „Ebenen“ von Cloud Computing anbieten: SaaS (Software as a Service) – die Bereitstellung von kompletten Fachanwendungen z.B. aus der eBusiness Suite in Form eines Mietmodells - gab es schon länger. Abgesehen von der Tatsache, dass hier zusätzliche/neuere Komponenten und Module der durch die letzten Zukäufe von Oracle noch breiter gewordenen Palette angeboten werden, ändert sich am Prinzip nichts. Bei PaaS (Plattform as a Service) sind vor allem die beiden bereits letztes Jahr angekündigten Dienste „Database Service“ (basierend auf APEX) und „Java Service“ (basierend auf Weblogic) zu nennen, für die nun auch konkrete Pakete und Preise (ca.175$ bis 2000$/Monat) sowie die Möglichkeit zur Anmeldung auf http://cloud.oracle.com vorliegen. Interessanterweise gehört auch ein sog. „Social Service“ in diese Schicht, mit der Oracle Kunden ihre Anwendungen in Zukunft auf standardisierte Weise durch Social Networking Funktionalität wie z.B. Microblogging erweitern können.Ebenso neu angekündigt wurde ein "Developer Service", welcher z.B. Sourcecode-Verwaltung durch GIT Repositories sowie Wikis und Issue Tracking bereit stellen soll. Die dort mittels JDeveloper, Netbeans oder Eclipse erstellten Applikationen können dann nahtlos innerhalb kürzester Zeit in den Java Service deployed werden. Komplett neu und für einige sicher überraschend ist hingegen der Bereich IaaS (Infrastructure as a Service) – Hier geht es um die Bereitstellung von Basis-Infrastrukturkomponenten wie Storage, Rechenleistung (letztlich also Betriebssysteme / VMs) und Messaging / Queueing. Genaue Details oder Preise zu den IaaS Angeboten sind noch nicht bekannt, aber zumindest zu den Storage- und Messaging Services können grundlegende Daten bereits auf http://cloud.oracle.com eingesehen werden Die zweite Neuerung: Kunden können in Zukunft als Alternative zum Betrieb der o.g. „Oracle Cloud“, diese auch komplett hinter ihrer eigenen Firewall aufbauen lassen. Mit anderen Worten: Oracle baut und betreibt bei diesem als „Oracle Private Cloud“ bezeichneten Angebot alle Komponenten selbst – die Daten verlassen aber niemals das Gebäude des Kunden. Letzteres ist gerade bei uns im Datenschutz-sensiblen Deutschland ein wichtiger Aspekt. Da die verwendeten Komponenten in beiden Fällen die gleichen sind, ist auch ein „Umziehen“ oder Erweitern der Private Cloud in die Public Cloud (oder zurück) ohne Änderungen an den Anwendungen möglich. Der Möglichkeit einer "Hybrid Cloud", bei der Teile einer Anwendung hinter der eigenen Firewall, andere Teile aber in der Oracle Cloud laufen, wird damit Realität.

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• Apache MaxClients reaching max and locking the server

  - by Rodrigo Sieiro

  Hi. I currently have an Apache2 server running with mpm-prefork and mod_php on a OpenVZ VPS with 512M real / 1024M burstable RAM (no swap). After running some tests, I found that the maximum process size Apache gets is 23M, so I've set MaxClients to 25 (23M x 25 = 575 MB, ok for me). I decided to run some load tests on my server, and the results left me puzzled. I'm using ab on my desktop machine requesting the main page from a wordpress blog. When I run ab with 24 concurrent connections, everything seems fine. Sure, CPU goes up, free RAM goes down, and the result is about 2-3s response time per request. But if I run ab with 25 concurrent connections (my server limit), Apache just hangs after a couple of seconds. It starts processing the requests, then it stops responding, CPU goes back to 100% idle and ab times out. Apache log says it reached MaxClients. When this happens, Apache keeps itself locked up with 25 running processes (they're all in "W" if I check server status) and only after the TimeOut setting the processes start to die and the server starts responding again (in my case it's set to 45). My question: is that expected behaviour? Why Apache just dies when it reaches MaxClients? If it works with 24 connections, shouldn't it work with 25, just taking maybe more time to respond each request and queueing up the rest? It sounds kinda strange to me that any kid running ab can alone kill a webserver just by setting the concurrent connections to the servers MaxClients.

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• Apache reaching MaxClients and locking the server

  - by Rodrigo Sieiro

  Hi. I currently have an Apache2 server running with mpm-prefork and mod_php on a OpenVZ VPS with 512M real / 1024M burstable RAM (no swap). After running some tests, I found that the maximum process size Apache gets is 23M, so I've set MaxClients to 25 (23M x 25 = 575 MB, ok for me). I decided to run some load tests on my server, and the results left me puzzled. I'm using ab on my desktop machine requesting the main page from a wordpress blog. When I run ab with 24 concurrent connections, everything seems fine. Sure, CPU goes up, free RAM goes down, and the result is about 2-3s response time per request. But if I run ab with 25 concurrent connections (my server limit), Apache just hangs after a couple of seconds. It starts processing the requests, then it stops responding, CPU goes back to 100% idle and ab times out. Apache log says it reached MaxClients. When this happens, Apache keeps itself locked up with 25 running processes (they're all in "W" if I check server status) and only after the TimeOut setting the processes start to die and the server starts responding again (in my case it's set to 45). My question: is that expected behaviour? Why Apache just dies when it reaches MaxClients? If it works with 24 connections, shouldn't it work with 25, just taking maybe more time to respond each request and queueing up the rest? It sounds kinda strange to me that any kid running ab can alone kill a webserver just by setting the concurrent connections to the servers MaxClients.

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• Abnormally high amount of Transmit discards reported by Solarwinds for multiple switches

  - by Jared

  I have several 3750X Cisco switches that, according to our Solarwinds NPM, are producing billions of transmit discards per day. I'm not sure why it's reporting these discards. Many of the ports on the 3750X's have 2960's connected to them and are hardcoded as trunk ports. Solarwinds NPM version 10.3 Cisco IOS version 12.2(58)SE2 Total output drops: 29139431: GigabitEthernet1/0/43 is up, line protocol is up (connected) Hardware is Gigabit Ethernet, address is XXXX (bia XXXX) Description: XXXX MTU 1500 bytes, BW 100000 Kbit/sec, DLY 100 usec, reliability 255/255, txload 1/255, rxload 1/255 Encapsulation ARPA, loopback not set Keepalive set (10 sec) Full-duplex, 100Mb/s, media type is 10/100/1000BaseTX input flow-control is off, output flow-control is unsupported ARP type: ARPA, ARP Timeout 04:00:00 Last input 00:00:47, output 00:00:50, output hang never Last clearing of "show interface" counters 1w4d Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 29139431 Queueing strategy: fifo Output queue: 0/40 (size/max) 5 minute input rate 0 bits/sec, 0 packets/sec 5 minute output rate 35000 bits/sec, 56 packets/sec 51376 packets input, 9967594 bytes, 0 no buffer Received 51376 broadcasts (51376 multicasts) 0 runts, 0 giants, 0 throttles 0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored 0 watchdog, 51376 multicast, 0 pause input 0 input packets with dribble condition detected 115672302 packets output, 8673778028 bytes, 0 underruns 0 output errors, 0 collisions, 0 interface resets 0 unknown protocol drops 0 babbles, 0 late collision, 0 deferred 0 lost carrier, 0 no carrier, 0 pause output 0 output buffer failures, 0 output buffers swapped out sh controllers gigabitEthernet 1/0/43 utilization: Receive Bandwidth Percentage Utilization : 0 Transmit Bandwidth Percentage Utilization : 0

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• IIS 7.0 - responses throttled to 500ms blocks?

  - by Julia Hayward

  Scenario: ASP.NET MVC wep app sitting on my local machine (Vista Ultimate, IIS 7.0), nothing going on except one user (me) logged in and viewing an index page. The page includes 9 dynamic images drawn from the underlying DB and returned from a controller action. I have got the actual processing time for these images down to 15ms each. Turn on Firebug and watch the page load. What I see is 9 requests for images firing off together – no surprise – but four come back to me almost immediately; two more after 0.5s; another after 1s; then at 1.5s and 2s. Logging on the server side suggests the individual responses are still only taking 15ms. So it appears IIS is queueing things up into 500ms chunks. (Repeating the experiment produces different results, but each time the images return in similar blocks – you might get three in the first group, then three at 0.5s, two at 1s etc, for example – and it’s always at 500ms intervals, not anything else.) It’s also repeatable cross-browser, and it’s not repeatable with other forms of content. I haven't found any particular mention of this problem out there, so I'm sort of assuming it's not an IIS bug, so is it: i) IIS on desktop OSs deliberately does it, to make you use server OSs in production? ii) There is some magical setting that has eluded me for as long as I’ve known IIS? iii) Something peculiar to MVC or SQL Server 2008? or something else?

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• Why is my apache2, mod_fcgid, php configuration causing 100% cpu usage?

  - by Scott Lundgren

  Page load makes a quick initial connection, then hangs about 10 seconds before the page renders. When the server load goes up I start watching top & I see that both CPUs get pegged at times to 100% by between 4-8 processes of php-cgi. My theory is that since I never see RAM usage never go above 50%, that apache is able to handle the requests coming in, but is queueing them for PHP to process. What is wrong with my mod_fcgid/php configuration ? RHEL 5.4 2 Xeon E5420s @ 2.50 Ghz 4 Gb RAM Apache 2.2.3 Timeout 30 KeepAlive On MaxKeepAliveRequests 0 KeepAliveTimeout 5 <IfModule worker.c> StartServers 2 MaxClients 300 MinSpareThreads 25 MaxSpareThreads 75 ThreadsPerChild 25 MaxRequestsPerChild 0 </IfModule> mod_fcgid 2.2.10 LoadModule fcgid_module modules/mod_fcgid.so <IfModule !mod_fastcgi.c> AddHandler fcgid-script fcg fcgi fpl php </IfModule> SocketPath run/mod_fcgid SharememPath run/mod_fcgid/fcgid_shm DefaultInitEnv PHPRC "/etc/" FCGIWrapper /usr/bin/php-cgi .php MaxRequestsPerProcess 1500 MaxProcessCount 20 IPCCommTimeout 240 IdleTimeout 240 APC 3.0.19 extension = apc.so apc.enabled=1 apc.shm_segments=1 apc.optimization=0 apc.shm_size=32 apc.ttl=7200 APC cache is 43% used with a 99% hit rate

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• Linux: prevent outgoing TCP flood

  - by Willem

  I run several hundred webservers behind loadbalancers, hosting many different sites with a plethora of applications (of which I have no control). About once every month, one of the sites gets hacked and a flood script is uploaded to attack some bank or political institution. In the past, these were always UDP floods which were effectively resolved by blocking outgoing UDP traffic on the individual webserver. Yesterday they started flooding a large US bank from our servers using many TCP connections to port 80. As these type of connections are perfectly valid for our applications, just blocking them is not an acceptable solution. I am considering the following alternatives. Which one would you recommend? Have you implemented these, and how? Limit on the webserver (iptables) outgoing TCP packets with source port != 80 Same but with queueing (tc) Rate limit outgoing traffic per user per server. Quite an administrative burden, as there are potentially 1000's of different users per application server. Maybe this: how can I limit per user bandwidth? Anything else? Naturally, I'm also looking into ways to minimize the chance of hackers getting into one of our hosted sites, but as that mechanism will never be 100% waterproof, I want to severely limit the impact of an intrusion. Cheers!

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• MSMQ on Win2008 R2 won't receive messages from older clients

  - by Graffen

  I'm battling a really weird problem here. I have a Windows 2008 R2 server with Message Queueing installed. On another machine, running Windows 2003 is a service that is set up to send messages to a public queue on the 2008 server. However, messages never show up on the server. I've written a small console app that just sends a "Hello World" message to a test queue on the 2008 machine. Running this app on XP or 2003 results in absolutely nothing. However, when I try running the app on my Windows 7 machine, a message is delivered just fine. I've been through all sorts of security settings, disabled firewalls on all machines etc. The event log shows nothing of interest, and no exceptions are being thrown on the clients. Running a packet sniffer (WireShark) on the server reveals only a little. When trying to send a message from XP or 2003 I only see an ICMP error "Port Unreachable" on port 3527 (which I gather is an MQPing packet?). After that, silence. Wireshark shows a nice little stream of packets when I try from my Win7 client (as expected - messages get delivered just fine from Win7). I've enabled MSMQ End2End logging on the server, but only entries from the messages sent from my Win7 machine are appearing in the log. So somehow it seems that messages are being dropped silently somewhere along the route from XP or 2003 to my 2008 server. Does anyone have any clues as to what might be causing this mysterious behaviour? -- Jesper

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• MSMQ on Win2008 R2 won’t receive messages from older clients

  - by Graffen

  Hi all I'm battling a really weird problem here. I have a Windows 2008 R2 server with Message Queueing installed. On another machine, running Windows 2003 is a service that is set up to send messages to a public queue on the 2008 server. However, messages never show up on the server. I've written a small console app that just sends a "Hello World" message to a test queue on the 2008 machine. Running this app on XP or 2003 results in absolutely nothing. However, when I try running the app on my Windows 7 machine, a message is delivered just fine. I've been through all sorts of security settings, disabled firewalls on all machines etc. The event log shows nothing of interest, and no exceptions are being thrown on the clients. Running a packet sniffer (WireShark) on the server reveals only a little. When trying to send a message from XP or 2003 I only see an ICMP error "Port Unreachable" on port 3527 (which I gather is an MQPing packet?). After that, silence. Wireshark shows a nice little stream of packets when I try from my Win7 client (as expected - messages get delivered just fine from Win7). I've enabled MSMQ End2End logging on the server, but only entries from the messages sent from my Win7 machine are appearing in the log. So somehow it seems that messages are being dropped silently somewhere along the route from XP or 2003 to my 2008 server. Does anyone have any clues as to what might be causing this mysterious behaviour? -- Jesper

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• Messaging pattern question

  - by Al Bundy

  Process A is calculating values for objects a1, a2, a3 etc. and is sending results to the middleware queue (RabbitMQ). Consumers read the queue and process these results further. Periodically process A has to send a snapshot of these values, so consumers could do some other calculations. Values for these objects might change independently. The queue might look like this a1, a1, a2, a1, a2, a2, a3... Consumers process each item in the queue. The snapshot has to contain all objects and consumers will process this message for all objects in one go. So the requirement is to have a queue like this: a1, a1, a3, a2, a2, [snapshot, a1, a2, a3], a3, a1 ... The problem is that these items are of different types: one type for objects like a1, a2 and other for a snapshot. This means that they should be processed in a diferent queues, but in that case there is a race condition: consumers might process objects before processing a snapshot. Is there any pattern to solve this (quite common) problem? We are using RabbitMQ for message queueing.

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• MMS2R and Multiple Images Rails

  - by Maletor

  Here's my code: require 'mms2r' class IncomingMailHandler < ActionMailer::Base ## # Receives email(s) from MMS-Email or regular email and # uploads that content the user's photos. # TODO: Use beanstalkd for background queueing and processing. def receive(email) begin mms = MMS2R::Media.new(email) ## # Ok to find user by email as long as activate upon registration. # Remember to make UI option that users can opt out of registration # and either not send emails or send them to a [email protected] # type address. ## # Remember to get SpamAssasin if (@user = User.find_by_email(email.from) && email.has_attachments?) mms.media.each do |key, value| if key.include?('image') value.each do |file| @user.photos.push Photo.create!(:uploaded_data => File.open(file), :title => email.subject.empty? ? "Untitled" : email.subject) end end end end ensure mms.purge end end end and here's my error: /usr/local/lib/ruby/gems/1.8/gems/rails-2.3.4/lib/commands/runner.rb:48: undefined method photos' for true:TrueClass (NoMethodError) from /usr/home/xxx/app/models/incoming_mail_handler.rb:23:in each' from /usr/home/xxx/app/models/incoming_mail_handler.rb:23:in receive' from /usr/home/xxx/app/models/incoming_mail_handler.rb:21:in each' from /usr/home/xxx/app/models/incoming_mail_handler.rb:21:in receive' from /usr/local/lib/ruby/gems/1.8/gems/actionmailer-2.3.4/lib/action_mailer/base.rb:419:in receive' from (eval):1 from /usr/local/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:31:in eval' from /usr/local/lib/ruby/gems/1.8/gems/rails-2.3.4/lib/commands/runner.rb:48 from /usr/local/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:31:in gem_original_require' from /usr/local/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:31:in `require' from /home/xxx/script/runner:3 I sent an email to the server with two image attachments. Upon receiving the email the server runs "| ruby /xxx/script/runner 'IncomingMailHandler.receive STDIN.read'" What is going on? What am I doing wrong? MMS2R docs are here: http://mms2r.rubyforge.org/mms2r/

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• Ember Data Sycn - LocalStorage+REST+RealTime+Online/Offline

  - by Miguel Madero

  We have a combination of requirements in terms o data access. Pre-load some reference data. We need reference data to survive browser restarts instead of just living in memory to avoid loading it all the time. I'm currently using the LocalStorageAdapter for that. Once we have it, we would like to sync changes (polling or using Socket.IO in the background and updating the LocalStorage could do the trick) There're other models that are more transactional, where we would need to directly go to the Server and get/save them. It would be nice to use something like the RESTAdapter for that. Lastly, there're some operations that should work off-line and changes should be synced later. To make it more concrete: * We pre-load vendor and "favorite products" into Local Storage. We work offline with those. * We need to sync server changes to vendor and product information. * If they search the full catalog, that requires them to be online. * When offline, we need to allow users to add something to their cart or even submit and order. We would like to queue this action and submit it when they have an Internet Connection. So a few questions are derived from this: * Is there a way to user RESTAdapter in combination with LocalStorage? * Is there some Socket.IO support? (Happy to do this part manually) * Is there Queueing support? Ideally at the Ember-Data level. I know we will have to do a lot of this manually and pull together the different lego pieces, but I wanted to ask for some perspective from experience Ember devs.

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• How can I make hundreds of simultaneously running processes communicate with a database through one

  - by Olfan

  Long speech short: How can I make hundreds of simultaneously running processes communicate with a database through one or few permanent sessions? The whole story: I once built a number crunching engine that handles vast amounts of large data files by forking off one child after another giving each a small number of files to work on. File locking, progress monitoring and result propagation happen in an Oracle database which all (sub-)processes access at various times using an application-specific module which encapsulates DBI. This worked well at first, but now with higher volumes of input data, the number of database sessions (one per child, and they can be very short-lived) constantly being opened and closed is becoming an issue. I now want to centralise database access so that there are only one or few fixed database sessions which handle all database access for all the (sub-)processes. The presence of the database abstraction module should make the changes easy because the function calls in the worker instances can stay the same. My problem is that I cannot think of a suitable way to enhance said module in order to establish communication between all the processes and the database connector(s). I thought of message queueing, but couldn't come up with a way of connecting a large herd of requestors with one or few database connectors in a way so that bidirectional communication is possible (for collecting the query result). An asynchronous approach could help here in that all requests are written to the same queue and the database connector servicing the request will "call back" to submit the result. But my mind fails me in generating an image clear enough so that I can paint into code. Threading instead of forking might have given me an easier start, but this would now require massive changes to the code base that I'm not prepared to do to a live system. The more I think of it, the more the base idea looks like a pre-forked web server to me only that it doesn't serve web pages but database queries. Any ideas on what to dig into, and where? Sample (pseudo) code to inspire me, links to possibly related articles, ready solutions on CPAN maybe?

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• Consequent attribute calculations with a queuing system

  - by vrinek

  For all of the following assume these: rails v3.0 ruby v1.9 resque We have 3 models: Product belongs_to :sku, belongs_to :category Sku has_many :products, belongs_to :category Category has_many :products, has_many :skus When we update the product (let's say we disable it) we need to have some things happen to the relevant sku and category. The same is true for when a sku is updated. The proper way of achieving this is have an after_save on each model that triggers the other models' update events. example: products.each(&:disable!) # after_save triggers self.sku.products_updated # and self.category.products_updated (self is product) Now if we have 5000 products we are in for a treat. The same category might get updated hundreds of times and hog the database while doing so. We also have a nice queueing system, so the more realisting way of updating products would be products.each(&:queue_disable!) which would simply toss 5000 new tasks to the working queue. The problem of 5000 category updates still exists though. Is there a way to avoid all those updates on the db? How can we concatenate all the category.products_updated for each category in the queue?

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• Fastest reliable way for Clojure (Java) and Ruby apps to communicate

  - by jkndrkn

  Hi There, We have cloud-hosted (RackSpace cloud) Ruby and Java apps that will interact as follows: Ruby app sends a request to Java app. Request consists of map structure containing strings, integers, other maps, and lists (analogous to JSON). Java app analyzes data and sends reply to Ruby App. We are interested in evaluating both messaging formats (JSON, Buffer Protocols, Thrift, etc.) as well as message transmission channels/techniques (sockets, message queues, RPC, REST, SOAP, etc.) Our criteria: Short round-trip time. Low round-trip-time standard deviation. (We understand that garbage collection pauses and network usage spikes can affect this value). High availability. Scalability (we may want to have multiple instances of Ruby and Java app exchanging point-to-point messages in the future). Ease of debugging and profiling. Good documentation and community support. Bonus points for Clojure support. What combination of message format and transmission method would you recommend? Why? I've gathered here some materials we have already collected for review: Comparison of various java serialization options Comparison of Thrift and Protocol Buffers (old) Comparison of various data interchange formats Comparison of Thrift and Protocol Buffers Fallacies of Protocol Buffers RPC features Discussion of RPC in the context of AMQP (Message-Queueing) Comparison of RPC and message-passing in distributed systems (pdf) Criticism of RPC from perspective of message-passing fan Overview of Avro from Ruby programmer perspective

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• How to read from multiple queues in real-world?

  - by Leon Cullens

  Here's a theoretical question: When I'm building an application using message queueing, I'm going to need multiple queues support different data types for different purposes. Let's assume I have 20 queues (e.g. one to create new users, one to process new orders, one to edit user settings, etc.). I'm going to deploy this to Windows Azure using the 'minimum' of 1 web role and 1 worker role. How does one read from all those 20 queues in a proper way? This is what I had in mind, but I have little or no real-world practical experience with this: Create a class that spawns 20 threads in the worker role 'main' class. Let each of these threads execute a method to poll a different queue, and let all those threads sleep between each poll (of course with a back-off mechanism that increases the sleep time). This leads to have 20 threads (or 21?), and 20 queues that are being actively polled, resulting in a lot of wasted messages (each time you poll an empty queue it's being billed as a message). How do you solve this problem?

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• Disk is spinning down each minute, unable to disable it

  - by lzap

  I played with spindown and APM settings of my Samsung discs and now they spin down every minute. I want to disable it, but it seems it does not accept any of the spindown time or APM values. Nothing works, it's all the same. Please help what values should be proper for it. I do not want it to spin down at all. /dev/sda: ATA device, with non-removable media Model Number: SAMSUNG HD154UI Serial Number: S1Y6J1KZ206527 Firmware Revision: 1AG01118 Standards: Used: ATA-8-ACS revision 3b Supported: 7 6 5 4 Configuration: Logical max current cylinders 16383 16383 heads 16 16 sectors/track 63 63 -- CHS current addressable sectors: 16514064 LBA user addressable sectors: 268435455 LBA48 user addressable sectors: 2930277168 Logical/Physical Sector size: 512 bytes device size with M = 1024*1024: 1430799 MBytes device size with M = 1000*1000: 1500301 MBytes (1500 GB) cache/buffer size = unknown Capabilities: LBA, IORDY(can be disabled) Queue depth: 32 Standby timer values: spec'd by Standard, no device specific minimum R/W multiple sector transfer: Max = 16 Current = 16 Advanced power management level: 60 Recommended acoustic management value: 254, current value: 0 DMA: mdma0 mdma1 mdma2 udma0 udma1 udma2 udma3 udma4 udma5 *udma6 udma7 Cycle time: min=120ns recommended=120ns PIO: pio0 pio1 pio2 pio3 pio4 Cycle time: no flow control=120ns IORDY flow control=120ns Commands/features: Enabled Supported: * SMART feature set Security Mode feature set * Power Management feature set * Write cache * Look-ahead * Host Protected Area feature set * WRITE_BUFFER command * READ_BUFFER command * NOP cmd * DOWNLOAD_MICROCODE * Advanced Power Management feature set Power-Up In Standby feature set * SET_FEATURES required to spinup after power up SET_MAX security extension Automatic Acoustic Management feature set * 48-bit Address feature set * Device Configuration Overlay feature set * Mandatory FLUSH_CACHE * FLUSH_CACHE_EXT * SMART error logging * SMART self-test Media Card Pass-Through * General Purpose Logging feature set * 64-bit World wide name * WRITE_UNCORRECTABLE_EXT command * {READ,WRITE}_DMA_EXT_GPL commands * Segmented DOWNLOAD_MICROCODE * Gen1 signaling speed (1.5Gb/s) * Gen2 signaling speed (3.0Gb/s) * Native Command Queueing (NCQ) * Host-initiated interface power management * Phy event counters * NCQ priority information DMA Setup Auto-Activate optimization Device-initiated interface power management * Software settings preservation * SMART Command Transport (SCT) feature set * SCT Long Sector Access (AC1) * SCT LBA Segment Access (AC2) * SCT Error Recovery Control (AC3) * SCT Features Control (AC4) * SCT Data Tables (AC5) Security: Master password revision code = 65534 supported not enabled not locked frozen not expired: security count supported: enhanced erase 326min for SECURITY ERASE UNIT. 326min for ENHANCED SECURITY ERASE UNIT. Logical Unit WWN Device Identifier: 50024e900300cca3 NAA : 5 IEEE OUI : 0024e9 Unique ID : 00300cca3 Checksum: correct I have the very same disc which I did not "tuned" and it does not spin. But I do not know where to read the settings from. The hdparm only shows this: Advanced power management level: 60 Recommended acoustic management value: 254, current value: 0 Edit: It seems the issue was tuned daemon in RHEL6. It was too aggressive, I turned off disc tuning and it seems they are no longer spinning down.

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• Sendmail smtp-auth issues

  - by SlackO

  I'm running into a problem with Sendmail trying to implement SMTP- auth. I"m running 8.14.5 and have saslauthd running under FreeBSD 7.0-R. I don't believe I have starttls enabled (but I also compiled a version with it and have been testing it too - same problem) - just looking for basic auth, but am wondering if my configuration is not compatible with modern mail clients? I don't think I have any certs set up. It seems an older version of Microsoft Outlook Express works fine with SMTP-auth with no problems, but Outlook 2010 won't work, and neither will Eudora (basic settings to not use encryption and use same uid/pw as pop3 account name) When trying to send mail the server reports: "550 571 Relaying Denied. Proper authentication required." Is there some config that I am missing? Why does it work with Outlook Express but not other e-mail clients? my site.config.m4 has: APPENDDEF(confENVDEF',-DSASL=2') APPENDDEF(conf_sendmail_LIBS',-lsasl2') dnl APPENDDEF(confLIBDIRS',-L/usr/local/lib/sasl2') APPENDDEF(confLIBDIRS',-L/usr/local/lib') APPENDDEF(confINCDIRS',-I/usr/local/include') My sendmail.mc has: define(ConfAUTH_OPTIONS',A') TRUST_AUTH_MECH(LOGIN PLAIN')dnl define(ConfAUTH_MECHANISMS',`LOGIN PLAIN')dnl My /usr/local/lib/sasl2/Sendmail.conf has: pwcheck_method: saslauthd When I restart sendmail this shows up in the logs: Jun 16 12:36:24 x sm-mta[79090]: restarting /usr/sbin/sendmail due to signal Jun 16 12:36:24 x sm-mta[81145]: starting daemon (8.14.5): SMTP+queueing@00:30:00 Jun 16 12:36:24 x sm-mta[81147]: STARTTLS=client, relay=mxgw1.mail.nationalnet.com., version=TLSv1/SSLv3, verify=FAIL, cipher=DHE-RSA-AES256-SHA, bits=256/256 Jun 16 12:36:24 x sm-mta[81148]: STARTTLS=client, relay=mxgw1.mail.nationalnet.com., version=TLSv1/SSLv3, verify=FAIL, cipher=DHE-RSA-AES256-SHA, bits=256/256 testing on the cmd line: telnet localhost 587 Trying 127.0.0.1... Connected to localhost. Escape character is '^]'. 220 xxxt ESMTP Sendmail 8.14.5/8.14.5; Fri, 15 Jun 2012 18:28:03 -0500 (CDT) ehlo localhost 250-xxxx Hello localhost [127.0.0.1], pleased to meet you 250-ENHANCEDSTATUSCODES 250-PIPELINING 250-8BITMIME 250-SIZE 250-DSN 250-AUTH GSSAPI DIGEST-MD5 CRAM-MD5 LOGIN PLAIN 250-DELIVERBY 250 HELP I am not using any certs or ssl right now - just trying to get basic auth to work. Anyone have any ideas?

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• SPARC T4-4 Delivers World Record Performance on Oracle OLAP Perf Version 2 Benchmark

  - by Brian

  Oracle's SPARC T4-4 server delivered world record performance with subsecond response time on the Oracle OLAP Perf Version 2 benchmark using Oracle Database 11g Release 2 running on Oracle Solaris 11. The SPARC T4-4 server achieved throughput of 430,000 cube-queries/hour with an average response time of 0.85 seconds and the median response time of 0.43 seconds. This was achieved by using only 60% of the available CPU resources leaving plenty of headroom for future growth. The SPARC T4-4 server operated on an Oracle OLAP cube with a 4 billion row fact table of sales data containing 4 dimensions. This represents as many as 90 quintillion aggregate rows (90 followed by 18 zeros). Performance Landscape Oracle OLAP Perf Version 2 Benchmark 4 Billion Fact Table Rows System Queries/hour Users* Response Time (sec) Average Median SPARC T4-4 430,000 7,300 0.85 0.43 * Users - the supported number of users with a given think time of 60 seconds Configuration Summary and Results Hardware Configuration: SPARC T4-4 server with 4 x SPARC T4 processors, 3.0 GHz 1 TB memory Data Storage 1 x Sun Fire X4275 (using COMSTAR) 2 x Sun Storage F5100 Flash Array (each with 80 FMODs) Redo Storage 1 x Sun Fire X4275 (using COMSTAR with 8 HDD) Software Configuration: Oracle Solaris 11 11/11 Oracle Database 11g Release 2 (11.2.0.3) with Oracle OLAP option Benchmark Description The Oracle OLAP Perf Version 2 benchmark is a workload designed to demonstrate and stress the Oracle OLAP product's core features of fast query, fast update, and rich calculations on a multi-dimensional model to support enhanced Data Warehousing. The bulk of the benchmark entails running a number of concurrent users, each issuing typical multidimensional queries against an Oracle OLAP cube consisting of a number of years of sales data with fully pre-computed aggregations. The cube has four dimensions: time, product, customer, and channel. Each query user issues approximately 150 different queries. One query chain may ask for total sales in a particular region (e.g South America) for a particular time period (e.g. Q4 of 2010) followed by additional queries which drill down into sales for individual countries (e.g. Chile, Peru, etc.) with further queries drilling down into individual stores, etc. Another query chain may ask for yearly comparisons of total sales for some product category (e.g. major household appliances) and then issue further queries drilling down into particular products (e.g. refrigerators, stoves. etc.), particular regions, particular customers, etc. Results from version 2 of the benchmark are not comparable with version 1. The primary difference is the type of queries along with the query mix. Key Points and Best Practices Since typical BI users are often likely to issue similar queries, with different constants in the where clauses, setting the init.ora prameter "cursor_sharing" to "force" will provide for additional query throughput and a larger number of potential users. Except for this setting, together with making full use of available memory, out of the box performance for the OLAP Perf workload should provide results similar to what is reported here. For a given number of query users with zero think time, the main measured metrics are the average query response time, the median query response time, and the query throughput. A derived metric is the maximum number of users the system can support achieving the measured response time assuming some non-zero think time. The calculation of the maximum number of users follows from the well-known response-time law N = (rt + tt) * tp where rt is the average response time, tt is the think time and tp is the measured throughput. Setting tt to 60 seconds, rt to 0.85 seconds and tp to 119.44 queries/sec (430,000 queries/hour), the above formula shows that the T4-4 server will support 7,300 concurrent users with a think time of 60 seconds and an average response time of 0.85 seconds. For more information see chapter 3 from the book "Quantitative System Performance" cited below. -- See Also Quantitative System Performance Computer System Analysis Using Queueing Network Models Edward D. Lazowska, John Zahorjan, G. Scott Graham, Kenneth C. Sevcik external local Oracle Database 11g – Oracle OLAP oracle.com OTN SPARC T4-4 Server oracle.com OTN Oracle Solaris oracle.com OTN Oracle Database 11g Release 2 oracle.com OTN Disclosure Statement Copyright 2012, Oracle and/or its affiliates. All rights reserved. Oracle and Java are registered trademarks of Oracle and/or its affiliates. Other names may be trademarks of their respective owners. Results as of 11/2/2012.

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• Best practices for sending automated daily emails from web service

  - by Tauren

  I am running a web service that currently sends confirmation emails out to new users via the gmail smtp servers. As I'm only getting a few new users each day, this hasn't been a problem. I've recently added new features to the webapp that will require a customized message to be sent out to each user every day. Think of this as similar to the regular messages LinkedIn sends out that give you a status report on the activity in your network. Every user's message will be different. With thousands of users, this means thousands of unique messages will be sent each day. Edit: I've since found that these types of email are called "transactional or relationship messages". Spamtacular has a good article on differentiating between marketing and transactional email. I don't think using gmail's smtp servers will cut it anymore, but I don't know that for sure. I don't know what gmail's maximum outgoing messages per account is (it might be 100/day), but they limit outgoing mail to 500 recipients per message. I'm not sending a single message to 500 recipients, but I'm going to be sending 1000's of customized messages with each recipient getting one per day. I'm interested to learn any best practices for doing this (especially for Java-based webapps). Here are some of my thoughts and concerns on it: Should I set up my own outgoing mail server? If I do this, it seems like I'll have all sorts of other issues to worry about, such as preventing mail server abuse, monitoring bounces, allowing ways to opt-out of emails, etc. Are there any tools or services to help with this? Maybe something like OpenEMM or a services like MailChimp? But those seem focused more toward email marketing campaigns. I don't think I should have the webapp itself handle sending emails as it currently is for new user signups. I'm thinking I should setup a separate messaging server that can access the same backend/datastore as the webapp. Thoughts on this? Should I consider setting up some sort of message queueing service to help with this, such as JMS, RabbitMQ, ActiveMQ, etc.? Do I need to provide users a way to opt-out? Do I need to flag these as bulk messages? I don't really consider these email marketing messages, but I'm unsure what is considered appropriate or proper netiquette. Any advice is appreciated. I'm also very interested in open source tools or web services that simplify things and could help me to ramp up as quickly as possible. Thanks!

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• Speed Problem with Wireless Connectivity on Cisco 877w

  - by Carl Crawley

  Having a bit of a weird one with my local LAN setup. I recently installed a Cisco 877W router on my DSL2+ connection and all is working really well.. Upgraded the IOS to 12.4 and my wired clients are streaming connectivity superfast at 1.3mb/s. However, there seems to be an issue with my wireless clients - I can't seem to stream any data across the local wireless connection (LAN) and using the Internet, whilst responsive enough isn't really comparable with the wired connection speed. For example, all devices are connected to an 8 Port Gb switch on FE0 from the Router with a NAS disk and on my wired clients, I can transfer/stream etc absolutely fine - however, transferring a local 700Mb file on my local LAN estimates 7-8 hours to transfer :( The Wireless config is as follows : interface Dot11Radio0 description WIRELESS INTERFACE no ip address ! encryption mode ciphers tkip ! ssid [MySSID] ! speed basic-1.0 basic-2.0 basic-5.5 6.0 9.0 basic-11.0 channel 2462 station-role root rts threshold 2312 world-mode dot11d country GB indoor bridge-group 1 bridge-group 1 subscriber-loop-control bridge-group 1 spanning-disabled bridge-group 1 block-unknown-source no bridge-group 1 source-learning no bridge-group 1 unicast-flooding All devices are connected to the Gb Switch which is connected to FE0 with the following: Hardware is Fast Ethernet, address is 0021.a03e.6519 (bia 0021.a03e.6519) Description: Uplink to Switch MTU 1500 bytes, BW 100000 Kbit/sec, DLY 100 usec, reliability 255/255, txload 1/255, rxload 1/255 Encapsulation ARPA, loopback not set Keepalive set (10 sec) Full-duplex, 100Mb/s ARP type: ARPA, ARP Timeout 04:00:00 Last input never, output never, output hang never Last clearing of "show interface" counters never Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0 Queueing strategy: fifo Output queue: 0/40 (size/max) 5 minute input rate 14000 bits/sec, 19 packets/sec 5 minute output rate 167000 bits/sec, 23 packets/sec 177365 packets input, 52089562 bytes, 0 no buffer Received 919 broadcasts, 0 runts, 0 giants, 0 throttles 260 input errors, 260 CRC, 0 frame, 0 overrun, 0 ignored 0 input packets with dribble condition detected 156673 packets output, 106218222 bytes, 0 underruns 0 output errors, 0 collisions, 2 interface resets 0 babbles, 0 late collision, 0 deferred 0 lost carrier, 0 no carrier 0 output buffer failures, 0 output buffers swapped out Not sure why I'm having problems on the wireless and I've reached the end of my Cisco knowledge... Thanks for any pointers! Carl

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• Job queue manager with RPC interface

  - by admr

  I need a job queue manager that I can control over the Internet. It should be able to execute and stop processes, check on their status (ideally notice and execute some code when a process exits), respond to commands and also be able to report back to a server. Background: I have a GWT application that allows to create jobs to execute on a cloud instance (currently EC2). I want to push a "job packet" (data for a process to operate on etc) to S3, start a Linux EC2 instance (or use one that's already running), and tell a job manager on the instance to execute that job (possibly parallel to other jobs). It should then pull the "job packet" from S3, run a process that operates on that data and report back to the server that is running the server part of my GWT application with some information (e.g. exit code, stdout, stderr). If I have to write e.g. stdour/err to a file from the process and read that file, that's OK too. I would really like the manager to be "close" to the processes it runs, meaning I want to avoid using something like Runtime.exec from the JDK. It seems like I would have to do that if I used Quartz for example. I'm fine with the calls in both directions being asynchronous. I'm fine with any reasonable technology for the calls as long as I can easily build an interface for that in my GWT server side (e.g. HTTP requests to a servlet over SSL would be nice and trivial). The job manager does not need to have a very sophisticated queueing system. Running several processes either sequentially or in parallel should be fine. Determining how much compute time a process received during its lifetime would be nice (AFAIK, this might be challenging). I did not yet find any existing software that does this, including http://java-source.net/open-source/job-schedulers. I suspect I might have to build an RPC interface (with authentication etc, of course) around a job manager; maybe use something like Apache Commons Exec. In that case, I would prefer Java or Python for the job manager part. I would be happy to hear suggestions for either the former or latter scenario!

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• Why does every thread in my application use a different hibernate session?

  - by Ittai

  Hi, I have a web-application which uses hibernate and for some reason every thread (httprequest or other threads related to queueing) uses a different session. I've implemented a HibernateSessionFactory class which looks like this: public class HibernateSessionFactory { private static final ThreadLocal<Session> threadLocal = new ThreadLocal<Session>(); private static Configuration configuration = new AnnotationConfiguration(); private static org.hibernate.SessionFactory sessionFactory; static { try { configuration.configure(configFile); sessionFactory = configuration.buildSessionFactory(); } catch (Exception e) {} } private HibernateSessionFactory() {} public static Session getSession() throws HibernateException { Session session = (Session) threadLocal.get(); if (session == null || !session.isOpen()) { if (sessionFactory == null) { rebuildSessionFactory();//This method basically does what the static init block does } session = (sessionFactory != null) ? sessionFactory.openSession(): null; threadLocal.set(session); } return session; } //More non relevant methods here. Now from my testing it seems that the threadLocal member is indeed initialized only once when the class is first loaded by the JVM but for some reason when different threads access the getSession() method they use different sessions. When a thread first accesses this class (Session) threadLocal.get(); will return null but as expected all other access requests will yeild the same session. I'm not sure how this can be happening as the threadLocal variable is final and the method threadLocal.set(session) is only used in the above context (which I'm 99.9% sure has to yeild a non null session as I would have encountered a NullPointerException at a different part of my app). I'm not sure this is relevant but these are the main parts of my hibernate.cfg.xml file: <hibernate-configuration> <session-factory> <property name="connection.url">someURL</property> <property name="connection.driver_class"> com.microsoft.sqlserver.jdbc.SQLServerDriver</property> <property name="dialect">org.hibernate.dialect.SQLServerDialect</property> <property name="hibernate.connection.isolation">1</property> <property name="hibernate.connection.username">User</property> <property name="hibernate.connection.password">Password</property> <property name="hibernate.connection.pool_size">10</property> <property name="show_sql">false</property> <property name="current_session_context_class">thread</property> <property name="hibernate.hbm2ddl.auto">update</property> <property name="hibernate.cache.use_second_level_cache">false</property> <property name="hibernate.cache.provider_class">org.hibernate.cache.NoCacheProvider</property> <!-- Mapping files --> I'd appreciate any help granted and of course if anyone has any questions I'd be happy to clarify. Ittai

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• Print driver installs failing

  - by Kasius

  All of the Windows 7 64-bit Enterprise machines in my organization are failing to install a good number of printer drivers that previously installed without issue. This only happens with printer drivers. And not with all printer drivers. Just some. Network drivers, video drivers, etc. have had no problems. Here is part of setupapi.dev.log for a Dymo LabelWriter printer driver that is failing to install: dvi: {Plug and Play Service: Device Install for USBPRINT\DYMOLABELWRITER_450_TURBO\6&538F51D&0&USB001} ump: Creating Install Process: DrvInst.exe 09:36:58.071 ndv: Infpath=C:\Windows\INF\oem0.inf ndv: DriverNodeName=dymo.inf:DYMO.NTamd64.6.0:LW_450_TURBO_VISTA:8.1.0.363:usbprint\dymolabelwriter_450_aa08 ndv: DriverStorepath=C:\Windows\System32\DriverStore\FileRepository\dymo.inf_amd64_neutral_3a631b118b7a5828\dymo.inf ndv: Building driver list from driver node strong name... dvi: Searching for hardware ID(s): dvi: usbprint\dymolabelwriter_450_aa08 dvi: dymolabelwriter_450_aa08 inf: Opened PNF: 'C:\Windows\System32\DriverStore\FileRepository\dymo.inf_amd64_neutral_3a631b118b7a5828\dymo.inf' ([strings]) dvi: Selected driver installs from section [LW_450_TURBO_VISTA] in 'c:\windows\system32\driverstore\filerepository\dymo.inf_amd64_neutral_3a631b118b7a5828\dymo.inf'. dvi: Class GUID of device changed to: {4d36e979-e325-11ce-bfc1-08002be10318}. dvi: Set selected driver complete. ndv: {Core Device Install} 09:36:58.133 inf: Opened INF: 'C:\Windows\INF\oem0.inf' ([strings]) inf: Saved PNF: 'C:\Windows\INF\oem0.PNF' (Language = 0409) dvi: {DIF_ALLOW_INSTALL} 09:36:58.164 dvi: Using exported function 'ClassInstall32' in module 'C:\Windows\system32\ntprint.dll'. dvi: Class installer == ntprint.dll,ClassInstall32 dvi: No CoInstallers found dvi: Class installer: Enter 09:36:58.164 dvi: Class installer: Exit dvi: Default installer: Enter 09:36:58.180 dvi: Default installer: Exit dvi: {DIF_ALLOW_INSTALL - exit(0xe000020e)} 09:36:58.180 ndv: Installing files... dvi: {DIF_INSTALLDEVICEFILES} 09:36:58.180 dvi: Class installer: Enter 09:36:58.180 inf: Opened INF: 'C:\Windows\System32\DriverStore\FileRepository\dymo.inf_amd64_neutral_3a631b118b7a5828\dymo.inf' ([strings]) inf: Opened INF: 'C:\Windows\System32\DriverStore\FileRepository\dymo.inf_amd64_neutral_3a631b118b7a5828\dymo.inf' ([strings]) !!! dvi: Class installer: failed(0x00000490)! !!! dvi: Error 1168: Element not found. dvi: {DIF_INSTALLDEVICEFILES - exit(0x00000490)} 09:37:22.063 ndv: Device install status=0x00000490 ndv: Performing device install final cleanup... ! ndv: Queueing up error report since device installation failed... ndv: {Core Device Install - exit(0x00000490)} 09:37:22.063 dvi: {DIF_DESTROYPRIVATEDATA} 09:37:22.063 dvi: Class installer: Enter 09:37:22.063 dvi: Class installer: Exit dvi: Default installer: Enter 09:37:22.063 dvi: Default installer: Exit dvi: {DIF_DESTROYPRIVATEDATA - exit(0xe000020e)} 09:37:22.063 ump: Server install process exited with code 0x00000490 09:37:22.063 ump: {Plug and Play Service: Device Install exit(00000490)} Notice these lines in particular: !!! dvi: Class installer: failed(0x00000490)! !!! dvi: Error 1168: Element not found. dvi: {DIF_INSTALLDEVICEFILES - exit(0x00000490)} 09:37:22.063 ndv: Device install status=0x00000490 From what I have read, the "Element not found" error should be accompanied by an event describing what element was not found. The error that appears in Device Manager is "The driver cannot be installed because it is either not digitally signed or not signed in the appropriate manner." It appears to be signed fine though. It has an accompanying .CAT file and worked previously. And when installing, the following messages are logged in setupapi.dev.log: sto: {DRIVERSTORE_IMPORT_NOTIFY_VALIDATE} 09:36:56.277 inf: Opened INF: 'C:\Windows\System32\DriverStore\Temp\{272e2305-961c-7942-9ede-966f01047043}\dymo.inf' ([strings]) sig: {_VERIFY_FILE_SIGNATURE} 09:36:56.292 sig: Key = dymo.inf sig: FilePath = C:\Windows\System32\DriverStore\Temp\{272e2305-961c-7942-9ede-966f01047043}\dymo.inf sig: Catalog = C:\Windows\System32\DriverStore\Temp\{272e2305-961c-7942-9ede-966f01047043}\DYMO.CAT sig: Success: File is signed in catalog. sig: {_VERIFY_FILE_SIGNATURE exit(0x00000000)} 09:36:56.355 sto: Validating driver package files against catalog 'DYMO.CAT'. sto: Driver package is valid. sto: {DRIVERSTORE_IMPORT_NOTIFY_VALIDATE exit(0x00000000)} 09:36:56.402 sto: Verified driver package signature: sto: Digital Signer Score = 0x0D000005 sto: Digital Signer Name = Microsoft Windows Hardware Compatibility Publisher Now here's where it gets strange. If I take it off the domain, it installs fine. But it doesn't seem to have anything to do with Group Policy. I moved the machine to an OU that blocks inheritance, ran a gpupdate, ran rsop.msc to verify, and tried again. And it still didn't work. Likewise, I removed a machine from the domain, manually set all of the domain Group Policy settings in gpedit.msc, and tried that way, and it worked fine. So it seems like the Group Policy settings are irrelevant. What other domain-related issue could be causing this though? Any ideas on what to try next would be greatly appreciated. I'm not sure where to go from here. Thanks!

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• Limiting TCP sends with a "to-be-sent" queue and other design issues.

  - by Poni

  Hello all! This question is the result of two other questions I've asked in the last few days. I'm creating a new question because I think it's related to the "next step" in my understanding of how to control the flow of my send/receive, something I didn't get a full answer to yet. The other related questions are: http://stackoverflow.com/questions/3028376/an-iocp-documentation-interpretation-question-buffer-ownership-ambiguity http://stackoverflow.com/questions/3028998/non-blocking-tcp-buffer-issues In summary, I'm using Windows I/O Completion Ports. I have several threads that process notifications from the completion port. I believe the question is platform-independent and would have the same answer as if to do the same thing on a *nix, *BSD, Solaris system. So, I need to have my own flow control system. Fine. So I send send and send, a lot. How do I know when to start queueing the sends, as the receiver side is limited to X amount? Let's take an example (closest thing to my question): FTP protocol. I have two servers; One is on a 100Mb link and the other is on a 10Mb link. I order the 100Mb one to send to the other one (the 10Mb linked one) a 1GB file. It finishes with an average transfer rate of 1.25MB/s. How did the sender (the 100Mb linked one) knew when to hold the sending, so the slower one wouldn't be flooded? Another way to ask this: Can I get a "hold-your-sendings" notification from the remote side? Is it built-in in TCP or the so called "reliable network protocol" needs me to do so? Again, I have a loop with many sends to a remote server, and at some point, within that loop I'll have to determine if I should queue that send or I can pass it on to the transport layer (TCP). How do I do that? What would you do? Of course that when I get a completion notification from IOCP that the send was done I'll issue other pending sends, that's clear. Another design question related to this: Since I am to use a custom buffers with a send queue, and these buffers are being freed to be reused (thus not using the "delete" keyword) when a "send-done" notification has been arrived, I'll have to use a mutual exlusion on that buffer pool. Using a mutex slows things down, so I've been thinking; Why not have each thread have its own buffers pool, thus accessing it , at least when getting the required buffers for a send operation, will require no mutex, because it belongs to that thread only. The buffers pool is located at the thread local storage (TLS) level. No mutual pool implies no lock needed, implies faster operations BUT also implies more memory used by the app, because even if one thread already allocated 1000 buffers, the other one that is sending right now and need 1000 buffers to send something will need to allocated these to its own. This is a long question and I hope none got hurt (: Thank you all!

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