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• aio_write on linux with rtkaio is sometimes long

  - by Drakosha

  I'm using async io on linux with rtkaio library. In my tests everything works perfectly, but, in my real application i see that aio_write which is supposed to return very fast, is very slow. It can take more than 100 milis to write a 128KB to a O_DIRECT padded file. Both my test and the application use same I/O size, i check on the same file system (GFS). I added counting and i see that there are about 50% of async io operations that are short (shorter then 2 milis) and 50% that are long (longer than 2 milis). I also checked that the test and the application both use the same rtkaio library. I'm pretty lost, anyone any ideas where should i look? Another my related question: http://stackoverflow.com/questions/1799537/proc-sys-fs-aio-nr-is-never-higher-than-1024-aio-on-linux

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• Drawbacks with reading and writing a big file to or from disk at once instead of small chunks?

  - by Johann Gerell

  I work mainly on Windows and Windows CE based systems, where CreateFile, ReadFile and WriteFile are the work horses, no matter if I'm in native Win32 land or in managed .Net land. I have so far never had any obvious problem writing or reading big files in one chunk, as opposed to looping until several smaller chunks are processed. I usually delegate the IO work to a background thread that notifies me when it's done. But looking at file IO tutorials or "textbook examples", I often find the "loop with small chunks" used without any explanation of why it's used instead of the more obvious (I dare to say!) "do it all at once". Are there any drawbacks to the way I do that I haven't understood?

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• Java: opening and reading from a file without locking it.

  - by rogue780

  I need to be able to mimic 'tail -f' with Java. I'm trying to read a log file as it's being written by another process, but when I open the file to read it, it locks the file and the other process can't write to it anymore. Any help would be greatly appreciated! Here is the code that I'm using currently: public void read(){ Scanner fp = null; try{ fp = new Scanner(new FileReader(this.filename)); fp.useDelimiter("\n"); }catch(java.io.FileNotFoundException e){ System.out.println("java.io.FileNotFoundException e"); } while(true){ if(fp.hasNext()){ this.parse(fp.next()); } } }

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• Ruby: Read large data from stdout and stderr of an external process on Windows

  - by BinaryMuse

  Greetings, all, I need to run a potentially long-running process from Ruby on Windows and subsequently capture and parse the data from the external process's standard output and error. A large amount of data can be sent to each, but I am only necessarily interested in one line at a time (not capturing and storing the whole of the output). After a bit of research, I found that the Open3 class would take care of executing the process and giving me IO objects connected to the process's standard output and error (via popen3). Open3.popen3("external-program.bat") do |stdin, out, err, thread| # Step3.profit() ? end However, I'm not sure how to continually read from both streams without blocking the program. Since calling IO#readlines on out or err when a lot of data has been sent results in a memory allocation error, I'm trying to continuously check both streams for available input, but not having much luck with any of my implementations. Thanks in advance for any advice!

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• In Java how do a read an input stream in to a string?

  - by Johnny Maelstrom

  If you have an java.io.InputStream object how should you process that object and produce a string.

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• Hard drive write speed - finding a lighter antivirus?

  - by Shingetsu

  I recently have been getting a lot of system lag here (for example, the mouse and the display in general take about 15 seconds to react in the worst cases). After a lot of monitoring the resources, I found that the problem mainly happens when too much Disk I/O is being done. Three culprits have been identified: My browser had the highest write I/O with 35,000,000 I/O Write Bytes. Steam had the highest read I/O (when IDLE!!!) with 106,000,000 I/O Read Bytes. My antivirus (in both cases I will soon mention) was the runner up in both cases with: 30,000,000ish write and 80,000,000ish read. The first AV I had was Avast! which I had liked on my previous system. After noticing it taking so much I/O I switched to Panda (supposing it wouldn't use TOO much during idle phase). However it only used a bit less I/O. Just a lot less memory and cpu and somewhat more network. My browser at the moment is Maxthon 3 (which I like a lot). Before this I was running chrome which had similar data and much higher cpu when running in the background was enabled. I'm not going to be running steam all the time and there aren't many alternatives to it. I like my browser very much, but I AM willing to switch if there's an obvious problem (I'm in programming, however I'm not a very good sysadmin, especially not when it comes to windows). Finally, my system almost stops lagging when I turn off the antivirus (and preferably steam) (some remains but once in every 5-6 hours for a few seconds so it isn't a big problem). My question (has a few parts): Is it possible to configure steam to lower it's I/O usage? (and maybe network while we're at it?) Which antivirus (very preferably free) uses lowest I/O while idle (I leave PC alone during active scans so that isn't a problem). Is there an obvious problem with my current browser and, if so, is there a way to fix it or should I switch and, if so, to what? (P.S. I've been on FFox for some time too). Info on system: Windows 7 (32 bit T_T, I am getting a new one in a few months but I want to keep using system during that time though). Hard Drive (main) is a Raid0. (Also have an external 1TB one which contains steam (and steam alone). As such it doesn't get used by much anything other than steam and isn't a very large problem. However steam still uses some I/O of registry) CPU: Intel(R) Core(TM)2 CPU [email protected] RAM: 6GB (3.25GB usable) (this and CPU have little effect as shown in next section) Additional info: Memory usage during problematic times: 44% CPU usage during problematic times: 35% Page File: main drive: system managed. 1TB drive: none. The current system I'm using is about 6 years old and is mainly a place holder while I await the new one in a few months. Final words: this is my 1st post on Super User (this question wouldn't feel right on Stack Overflow where I usually stay). If it doesn't have it's place here please tell me. If anything is wrong with it, same. Edit Technically I'm looking for a live thread detection program with minimal IO usage. I already have good active scan capability: Kaspersky (the free scanner uses the paid database) and MalwareBytes. Edit 2 Noticed another one, it seems that windows media player has been using stuff even when off! Turning it off and restarting now. If the problem is fixed I'll tell you guys. The reason I didn't notice it before was because I didn't have resource manager in front of me at the MOMENT of the problem. Now I did and it was at the very top of the list!

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• How can I make refactoring a priority for my team?

  - by Joseph Garland

  The codebase I work with daily has no automated tests, inconsistent naming and tons of comments like "Why is this here?", "Not sure if this is needed" or "This method isn't named right" and the code is littered with "Changelogs" despite the fact we use source control. Suffice it to say, our codebase could use refactoring. We always have tasks to fix bugs or add new features, so no time is put aside to refactor code to be better and more modular, and it doesn't seem to be a high priority. How can I demonstrate the value of refactoring such that it gets added to our task lists? Is it worth it to just refactor as I go, asking for forgiveness rather than permission?

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• How to close IOs?

  - by blackdog

  when i managed IO, i found a problem. i used to close it like this: try { // my code } catch (Exception e) { // my code } finally{ if (is != null) { is.close(); } } but the close method also would throw exception. if i have more than one IO, i have to close all of them. so the code maybe like this: try { // my code } catch (Exception e) { // my code } finally{ if (is1 != null) { is1.close(); } if(is2 != null{ is2.close(); } // many IOs } if is1.close() throws an exception, is2, is3 would not close itself. So i have to type many try-catch-finally to control them. is there other way to solve the problem?

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• Should I build a multi-threaded system that handles events from a game and sorts them, independently, into different threads based on priority?

  - by JonathonG

  Can I build a multi-threaded system that handles events from a game and sorts them, independently, into different threads based on priority, and is it a good idea? Here's more info: I am about to begin work on porting a mid-sized game from Flash/AS3 to Java so that I can continue development with multi-threading capabilities. Here's a small bit of background about the game: The game contains numerous asynchronous activities, such as "world updating" (the game environment is constantly changing based on a set of natural laws and forces), procedural generation of terrain, NPCs, quests, items, etc., and on top of that, the effects of all of the player's interactions with his environment are programmatically calculated in real time, based on a set of constantly changing "stats" and once again, natural laws and forces. All of these things going on at once, in an asynchronous manner, seem to lend themselves to multi-threading very well. My question is: Can I build some kind of central engine that handles the "stacking" of all of these events as they are triggered, and dynamically sorts them out amongst the available threads, and would it be a good idea? As an example: Essentially, every time something happens (IE, a magic missile being generated by a spell, or a bunch of plants need to grow to their next stage), instead of just processing that task right then and adding the new object(s) to a list of managed objects, send a reference to that event to a core "event handler" that throws it into a stack of all other currently queued events, which then sorts them out and orders them according to urgency, splits them between a number of available threads for as-fast-as-possible multithreaded execution.

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• Is there a java library / package analogous to <stdio.h>?

  - by Roboprog

  I have been doing Java on and off for about 14 years, and almost nothing else the last 6 years or so. I really hate the java.io package -- its legion of subclasses and adapters. I do like exceptions, rather than having to always poll "errno" and the like, but I could surely live without declared exceptions. Is there anything that functions like the Unix/ANSI stdio.h routines in C? I know we will never be rid of java.io and its conventions until java itself is retired, as they have metastasized throughout the many frameworks that have accreted to java. That said, I would like something that works kind of like this (let's call it package javax.stdio): Have a main utility class, perhaps FileStar, that can read and write files (or pipes), either text or binary, either sequentially or random access, with constructors that mimic fopen() and popen(). This class should have a load of useful methods that do things like fread(), fwrite(), fgets(), fputs(), fseek(), and whatever else (fprintf()?). Methods that are incompatible with the open/construct mode simply throw up (just like some of the collections classes/methods do when restricted). Then, have a bunch of interfaces that suggest how you intend to use the stream once you have created it: Sequential, RandomAccess, ReadOnly, WriteOnly, Text, Binary, plus combinations of these that make sense. Perhaps even have methods to return the appropriate type-cast (interface), throwing up if you have asked for something incompatible. For extra flavor, skip the declared exceptions -- e.g. - javax.stdio.IOException extends RuntimeException. Is there an open source project like this floating around?

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• Return value from Object match

  - by Hito_kun

  I'm, by no means, JS fluent, so forgive me if im asking for some really basic stuff, but I've not being able to find a proper answer to my question. Im writting my first Node.js (plus Extra Framework and Socket.io) app and Im having some fun setting up the server side of a FB-like messenger (surprise!!!). So, let's say I have this data structure to store online users(This is a JSON Array, but I'm not sure it is the best way to do it or should I go with Javascript Objects): [ { "site": 45, "users": [ { "idUser": 5, "idSocket": "qwe87r7w8qwe", "name": "Carlos Ray Norris" }, { "idUser": 6, "idSocket": "v8d9d0fgfs7d", "name": "John Connor" } ] }, { "site": 48, "users": [ { "idUser": 22, "idSocket": "qwe87r7w8qwe", "name": "David Bowie" }, { "idUser": 23, "idSocket": "v8d9d0fgfs7d", "name": "Barack H. Obama" } ] } ] What I want to do is to search in the array for x value given y. In this case, retrieving the idSocket knowing the idUser WITHOUT having to run through the array values. So I have basically 2 questions: first, what would be the proper way to store users online? and secondly, how to find values matching with the values I already know (find the idSocket that has a given idUser). I would like a pure JS approach(or using some of the tools given by Node, Socket.io or Express), but if that's not possible then I can look for some JQuery.

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• mysterical error

  - by Görkem Buzcu

  i get "customer_service_simulator.exe stopped" error, but i dont know why? this is my c programming project and i have limited time left before deadline. the code is: #include <stdio.h> #include <stdlib.h> #include<time.h> #define FALSE 0 #define TRUE 1 /*A Node declaration to store a value, pointer to the next node and a priority value*/ struct Node { int priority; //arrival time int val; //type int wait_time; int departure_time; struct Node *next; }; Queue Record that will store the following: size: total number of elements stored in the list front: it shows the front node of the queue (front of the queue) rear: it shows the rare node of the queue (rear of the queue) availability: availabity of the teller struct QueueRecord { struct Node *front; struct Node *rear; int size; int availability; }; typedef struct Node *niyazi; typedef struct QueueRecord *Queue; Queue CreateQueue(int); void MakeEmptyQueue(Queue); void enqueue(Queue, int, int); int QueueSize(Queue); int FrontOfQueue(Queue); int RearOfQueue(Queue); niyazi dequeue(Queue); int IsFullQueue(Queue); int IsEmptyQueue(Queue); void DisplayQueue(Queue); void sorteddequeue(Queue); void sortedenqueue(Queue, int, int); void tellerzfunctionz(Queue *, Queue, int, int); int main() { int system_clock=0; Queue waitqueue; int exit, val, priority, customers, tellers, avg_serv_time, sim_time,counter; char command; waitqueue = CreateQueue(0); srand(time(NULL)); fflush(stdin); printf("Enter number of customers, number of tellers, average service time, simulation time\n:"); scanf("%d%c %d%c %d%c %d",&customers, &command,&tellers,&command,&avg_serv_time,&command,&sim_time); fflush(stdin); Queue tellerarray[tellers]; for(counter=0;counter<tellers;counter++){ tellerarray[counter]=CreateQueue(0); //burada teller sayisi kadar queue yaratiyorum } for(counter=0;counter<customers;counter++){ priority=1+(int)rand()%sim_time; //this will generate the arrival time sortedenqueue(waitqueue,1,priority); //here i put the customers in the waiting queue } tellerzfunctionz(tellerarray,waitqueue,tellers,customers); DisplayQueue(waitqueue); DisplayQueue(tellerarray[0]); DisplayQueue(tellerarray[1]); // waitqueue-> printf("\n\n"); system("PAUSE"); return 0; } /*This function initialises the queue*/ Queue CreateQueue(int maxElements) { Queue q; q = (struct QueueRecord *) malloc(sizeof(struct QueueRecord)); if (q == NULL) printf("Out of memory space\n"); else MakeEmptyQueue(q); return q; } /*This function sets the queue size to 0, and creates a dummy element and sets the front and rear point to this dummy element*/ void MakeEmptyQueue(Queue q) { q->size = 0; q->availability=0; q->front = (struct Node *) malloc(sizeof(struct Node)); if (q->front == NULL) printf("Out of memory space\n"); else{ q->front->next = NULL; q->rear = q->front; } } /*Shows if the queue is empty*/ int IsEmptyQueue(Queue q) { return (q->size == 0); } /*Returns the queue size*/ int QueueSize(Queue q) { return (q->size); } /*Shows the queue is full or not*/ int IsFullQueue(Queue q) { return FALSE; } /*Returns the value stored in the front of the queue*/ int FrontOfQueue(Queue q) { if (!IsEmptyQueue(q)) return q->front->next->val; else { printf("The queue is empty\n"); return -1; } } /*Returns the value stored in the rear of the queue*/ int RearOfQueue(Queue q) { if (!IsEmptyQueue(q)) return q->rear->val; else { printf("The queue is empty\n"); return -1; } } /*Displays the content of the queue*/ void DisplayQueue(Queue q) { struct Node *pos; pos=q->front->next; printf("Queue content:\n"); printf("-->Priority Value\n"); while (pos != NULL) { printf("--> %d\t %d\n", pos->priority, pos->val); pos = pos->next; } } void enqueue(Queue q, int element, int priority){ if(IsFullQueue(q)){ printf("Error queue is full"); } else{ q->rear->next=(struct Node *)malloc(sizeof(struct Node)); q->rear=q->rear->next; q->rear->next=NULL; q->rear->val=element; q->rear->priority=priority; q->size++; } } void sortedenqueue(Queue q, int val, int priority) { struct Node *insert,*temp; insert=(struct Node *)malloc(sizeof(struct Node)); insert->val=val; insert->priority=priority; temp=q->front; if(q->size==0){ enqueue(q, val, priority); } else{ while(temp->next!=NULL && temp->next->priority<insert->priority){ temp=temp->next; } //printf("%d",temp->priority); insert->next=temp->next; temp->next=insert; q->size++; if(insert->next==NULL){ q->rear=insert; } } } niyazi dequeue(Queue q) { niyazi del; niyazi deli; del=(niyazi)malloc(sizeof(struct Node)); deli=(niyazi)malloc(sizeof(struct Node)); if(IsEmptyQueue(q)){ printf("Queue is empty!"); return NULL; } else { del=q->front->next; q->front->next=del->next; deli->val=del->val; deli->priority=del->priority; free(del); q->size--; return deli; } } void sorteddequeue(Queue q) { struct Node *temp; struct Node *min; temp=q->front->next; min=q->front; int i; for(i=1;i<q->size;i++) { if(temp->next->priority<min->next->priority) { min=temp; } temp=temp->next; } temp=min->next; min->next=min->next->next; free(temp); if(min->next==NULL){ q->rear=min; } q->size--; } void tellerzfunctionz(Queue *a, Queue b, int c, int d){ int i; int value=0; int priority; niyazi temp; temp=(niyazi)malloc(sizeof(struct Node)); if(c==1){ for(i=0;i<d;i++){ temp=dequeue(b); sortedenqueue((*(a)),temp->val,temp->priority); } } else{ for(i=0;i<d;i++){ while(b->front->next->val==1){ if((*(a+value))->availability==1){ temp=dequeue(b); sortedenqueue((*(a+value)),temp->val,temp->priority); (*(a+value))->rear->val=2; } else{ value++; } } } } } //end of the program

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• Disk performance below expectations

  - by paulH

  this is a follow-up to a previous question that I asked (Two servers with inconsistent disk speed). I have a PowerEdge R510 server with a PERC H700 integrated RAID controller (call this Server B) that was built using eight disks with 3Gb/s bandwidth that I was comparing with an almost identical server (call this Server A) that was built using four disks with 6Gb/s bandwidth. Server A had much better I/O rates than Server B. Once I discovered the difference with the disks, I had Server A rebuilt with faster 6Gbps disks. Unfortunately this resulted in no increase in the performance of the disks. Expecting that there must be some other configuration difference between the servers, we took the 6Gbps disks out of Server A and put them in Server B. This also resulted in no increase in the performance of the disks. We now have two identical servers built, with the exception that one is built with six 6Gbps disks and the other with eight 3Gbps disks, and the I/O rates of the disks is pretty much identical. This suggests that there is some bottleneck other than the disks, but I cannot understand how Server B originally had better I/O that has subsequently been 'lost'. Comparative I/O information below, as measured by SQLIO. The same parameters were used for each test. It's not the actual numbers that are significant but rather the variations between systems. In each case D: is a 2 disk RAID 1 volume, and E: is a 4 disk RAID 10 volume (apart from the original Server A, where E: was a 2 disk RAID 0 volume). Server A (original setup with 6Gpbs disks) D: Read (MB/s) 63 MB/s D: Write (MB/s) 170 MB/s E: Read (MB/s) 68 MB/s E: Write (MB/s) 320 MB/s Server B (original setup with 3Gpbs disks) D: Read (MB/s) 52 MB/s D: Write (MB/s) 88 MB/s E: Read (MB/s) 112 MB/s E: Write (MB/s) 130 MB/s Server A (new setup with 3Gpbs disks) D: Read (MB/s) 55 MB/s D: Write (MB/s) 85 MB/s E: Read (MB/s) 67 MB/s E: Write (MB/s) 180 MB/s Server B (new setup with 6Gpbs disks) D: Read (MB/s) 61 MB/s D: Write (MB/s) 95 MB/s E: Read (MB/s) 69 MB/s E: Write (MB/s) 180 MB/s Can anybody suggest any ideas what is going on here? The drives in use are as follows: Dell Seagate F617N ST3300657SS 300GB 15K RPM SAS Dell Hitachi HUS156030VLS600 300GB 3.5 inch 15000rpm 6GB SAS Hitachi Hus153030vls300 300GB Server SAS Dell ST3146855SS Seagate 3.5 inch 146GB 15K SAS

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• Delay before download starts when serving files using nginx

  - by glumbo

  I am currently using nginx to serve downloads off my website. Users sometimes need to wait about 5 seconds before their download starts after clicking a download link. I'm not sure if I need to start using raid 10 (I'm currently using raid 50) or if this is a problem with my nginx configuration. I am also on a 1gbit line but download sometimes go as low as 10kB/s. My server: Dual Xeon 5620 CPU, 12x2TB drives with 8GB ram. This is my nginx.conf #user nobody; worker_processes 12; worker_rlimit_nofile 10240; worker_rlimit_sigpending 32768; error_log logs/error.log crit; #pid logs/nginx.pid; events { worker_connections 2048; } http { include mime.types; default_type application/octet-stream; access_log off; limit_conn_log_level info; log_format xfs '$arg_id|$arg_usr|$remote_addr|$body_bytes_sent|$status'; #sendfile on; #tcp_nopush on; reset_timedout_connection on; server_tokens off; autoindex off; keepalive_timeout 0; #keepalive_timeout 65; limit_zone one $binary_remote_addr 10m; perl_modules perl; perl_require download.pm;

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• Measuring 'total bytes written' under Linux

  - by badnews

  We're quite interested in exploring the possibility of using SSD drives in a server environment. However, one thing that we need to establish is expected drive longevity. According to this article manufacturer's are reporting drive endurance in terms of 'total bytes written' (TBW). E.g. from that article a Crucial C400 SSD is rated at 72TB TBW. Do any scripts/tools exist under the Linux ecosystem to help us measure TBW? (and then make a more educated decision on the feasibility of using SSD drives)

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• Bad I/O scheduler?

  - by user62367

  os: up-to-date Fedora 14. Working as a "normal desktop". It's doing very well, but if i start VirtualBox, and e.g.: install a guest on it, it just "freezez". I mean if there are disk activities on a VirtualBox guest, then the computer becomes unrespondable..even the mouse is laggin for about 50 minutes.. What could be the bottleneck? What could be the problem? If anyone has any tips/howtos to speed it up, please help! It has a normal 2,5" HDD, with 5400 RPM. Does it worth for me if i buy a 2,5" HDD with 7200 RPM? T7200 cpu, 4 GByte RAM, "vm.swappiness = 0". Thank you!

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• Different block sizes for partition and underlying logical disk on HP Raid Controller (Linux)

  - by Wawrzek

  Following links collected in this thread I started to check blockdev and found the following output indicating different sizes for partition c0d9p1 and the underlying device (c0d9): [root@machine ~]# blockdev --report /dev/cciss/c0d9 RO RA SSZ BSZ StartSec Size Device rw 256 512 4096 0 3906963632 /dev/cciss/c0d9 [root@machine ~]# blockdev --report /dev/cciss/c0d9p1 RO RA SSZ BSZ StartSec Size Device rw 256 512 2048 1 3906959039 /dev/cciss/c0d9p1 We have a lot of small files, so yes the block size is smaller than normal. The device is a logical driver on an HP P410 raid controller, simple disk without any raid - RAID 0 on one disk to be precise. (Please note that above configuration is a feature not a bug). Therefore, I have the following questions. Can the above discrepancy in the block size affect disk performance? Can I control the block size using hpacucli?

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• How to identify heavy write to disk?

  - by Darth

  I have this problem with server running CakePHP application. The server is insanely slow, I first thought that it's application problem, but then I found constant 5-6MB/s write to disk. What is the easiest way to find cause of such a heavy write? The server is running Gentoo.

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• I/O intensive MySql server on Amazon AWS

  - by rhossi

  We recently moved from a traditional Data Center to cloud computing on AWS. We are developing a product in partnership with another company, and we need to create a database server for the product we'll release. I have been using Amazon Web Services for the past 3 years, but this is the first time I received a spec with this very specific hardware configuration. I know there are trade-offs and that real hardware will always be faster than virtual machines, and knowing that fact forehand, what would you recommend? 1) Amazon EC2? 2) Amazon RDS? 3) Something else? 4) Forget it baby, stick to the real hardware Here is the hardware requirements This server will be focused on I/O and MySQL for the statistics, memory size and disk space for the images hosting. Server 1 I/O The very main part on this server will be I/O processing, FusionIO cards have proven themselves extremely efficient, this is currently the best you can have in this domain. o Fusion ioDrive2 MLC 365GB (http://www.fusionio.com/load/-media-/1m66wu/docsLibrary/FIO_ioDrive2_Datasheet.pdf) CPU MySQL will use less CPU cores than Apache but it will use them very hard, the E7 family has 30M Cache L3 wichi provide boost performance : o 1x Intel E7-2870 will be ok. Storage SAS will be good enough in terms of performance, especially considering the space required. o RAID 10 of 4 x SAS 10k or 15k for a total available space of 512 GB. Memory o 64 GB minimum is required on this server considering the size of the statistics database. Warning: the statistics database will grow quickly, if possible consider starting with 128 GB directly, it will help. This server will be focused on I/O and MySQL for the statistics, memory size and disk space for the images hosting. Server 2 I/O The very main part on this server will be I/O processing, FusionIO cards have proven themselves extremely efficient, this is currently the best you can have in this domain. o Fusion ioDrive2 MLC 365GB (http://www.fusionio.com/load/-media-/1m66wu/docsLibrary/FIO_ioDrive2_Datasheet.pdf) CPU MySQL will use less CPU cores than Apache but it will use them very hard, the E7 family has 30M Cache L3 wichi provide boost performance : o 1x Intel E7-2870 will be ok. Storage SAS will be good enough in terms of performance, especially considering the space required. o RAID 10 of 4 x SAS 10k or 15k for a total available space of 512 GB. Memory o 64 GB minimum is required on this server considering the size of the statistics database. Warning: the statistics database will grow quickly, if possible consider starting with 128 GB directly, it will help. Thanks in advance. Best,

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• I/O APIC on Virtualbox

  - by RidDeBakTiYar

  I'm trying to use the PIT to do APIC timer calibration, and I want to use the PIT through I/O APIC instead of PIC. On Bochs I get interrupts from the PIT at the asked frequency from the I/O APIC, while on Virtualbox I can't receive a single interrupt. It must be an I/O APIC configuration problem because as I unmask the first PIC entry, the IRQ fires. However that's not what I want. Can you imagine any possible condition that wouldn't make Virtualbox fire the IRQ? I'm not assuming single I/O APIC configuration (even though Virtualbox has only 1). I'm not assuming identity mappings between ISA IRQs and I/O APIC GSIs (using ACPI MADT table to get I/O APIC base address and Int override). I'm setting the Trigger Mode and Polarity bits correctly (on Virtualbox they are set as '00 - default' which means edge high right?). I'm putting the BSP APIC ID into the Destination field (using Physical destination) and vector 0x20. Being the BSP APIC ID 0 on Virtualbox, it ends up with 0x0000000000000020 written to the IOREDTBL. And, just in case I'm getting the wrong values from the Interrupt Override descriptor, I'm setting this value to all the IOREDTBL entries (I know this is very very bad, and it wont be kept as I understand what's going on). The only thing I didn't check out is Local APIC configuration. Actually I'm not writing any value to the BSP LAPIC. Just reading the APIC ID and using it to boot APs through IPIs. And obviously I'm setting bit 11 in the IA32_APIC_BASE MSR to enable the LAPIC. Any ideas? Thanks in advance.

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• Will adding a SSD cache device to my ZFS storage improve performance?

  - by Sysadminicus

  The server has 4GB of RAM and my zpool is made up of 15.5k SAS drives arranged like this: NAME STATE READ WRITE CKSUM tank ONLINE 0 0 0 raidz1-0 ONLINE 0 0 0 c0t2d0 ONLINE 0 0 0 c0t3d0 ONLINE 0 0 0 c0t4d0 ONLINE 0 0 0 c0t5d0 ONLINE 0 0 0 c0t6d0 ONLINE 0 0 0 c0t7d0 ONLINE 0 0 0 c0t8d0 ONLINE 0 0 0 raidz1-1 ONLINE 0 0 0 c0t10d0 ONLINE 0 0 0 c0t11d0 ONLINE 0 0 0 c0t12d0 ONLINE 0 0 0 c0t13d0 ONLINE 0 0 0 c0t14d0 ONLINE 0 0 0 spares c0t9d0 AVAIL c0t1d0 AVAIL The primary use is as an NFS store for a couple VMWare ESXi servers. I can't do any "true" benchmarks because this is a production system (no budget for test systems), but using dd and bonnie++ I can't get more than ~40-50MB/s writes and ~70-90MB/s reads. It seems I should be able to do much better, but I'm not sure where to optimize. Based on what I've read, I think dropping in a OCZ Vertex 2 Pro SSD as my L2ARC is going to be the best bang-for-the-buck to improve througput. Is there something else I should be looking into to help performance? If not... How do I know how big a cache device I need? Am I safe with only a single SSD as my cache device?

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• Need data on disk drive management by OS: getting base I/O unit size, "sync" option, Direct Memory A

  - by Richard T

  Hello All, I want to ensure I have done all I can to configure a system's disks for serious database use. The three areas I know of (any others?) to be concerned about are: I/O size: the database engine and disk's native size should either match, or the database's native I/O size should be a multiple of the disk's native I/O size. Disks that are capable of Direct Memory Access (eg. IDE) should be configured for it. When a disk says it has written data persistently, it must be so! No keeping it in cache and lying about it. I have been looking for information on how to ensure these are so for CENTOS and Ubuntu, but can't seem to find anything at all! I want to be able to check these things and change them if needed. Any and all input appreciated.

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• RAID10 without write-back cache = horrible write performance?

  - by Harry Mexican

  I have just provisioned a dedicated server on singlehop. I'm running it through some tests to know what to expect performance-wise. On the I/O side (with 4 1TB disks in RAID 10) I get: write-cache disabled 200 MB/s read throughput 30 MB/s write throughput I thought that was really low compared to my desktop HD which gets 150-150 or so. So I had a chat with them and they suggested enabling the write cache. New results: write-cache enabled 280 MB/s read 260 MB/s write which is great and all but means I'd have to add a BBU for an additional monthly cost. Is it normal for the write throughput to be 1/4 of a regular drive on RAID10, if you don't have write cache? It almost feels like its intentionally bad to force you to pony up for the BBU. I'd be happy with normal non-raid performance of 150/150.

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• Try to delete files used by IIS

  - by Cédric Boivin

  I got a service coded in c# whoes deleted somes web site files hosted on iis, before an update. But sometime when i delete the files, they stay there. If I try to delete them manually, via explorer, the file are not deletable, because they are in state "Delete pending". There is the way my service try to delete the file try { // Enlève tout les attributs sur le fichiers afin de s'assurer que le fichier n'est pas en lecture seul File.SetAttributes(file, FileAttributes.Normal); // Supprime le fichier File.Delete(file); } It's there a way to avoid this state ? What can i do to force the delete by c# code? Could i release all process to the file by c# code ? The environnement is IIS 7.5 Windows 2008-r2 .net 4.0 Thanks

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• Windows Disk I/O Analysis

  - by Jonathon

  It appears that we are having a problem with the disk i/o speed on our Windows 2003 Enterprise Edition server (64-bit). As we were initializing a database that created two 1G tablespaces on 3 different machines, it became obvious that the two smaller machines (each 32-bit Windows 2003 Standard Edition with less RAM) killed the larger machine when creating the files. The larger machine took 10x as long to create the tablespaces than did the other machines. Now, I am left wondering how that could be. What programs or scripts would you guys recommend for tracking down the I/O problem? I think the issue may be with the controller card (all boxes are hardware RAID 10, but have different controller cards), but I would like to check the actual disk I/O speed as well, so I have some hard numbers to work with. Any help would be appreciated.

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