File Fragmentation And Disk Read Queue
May 16, 2008
I have a poorly performing SQL box.
I have run perfmon and the avg read queue length is pretty much permanently maxed out at 100%.
I have run a database index defrag.
On further inspection the file system is highly fragmented. There is a file fragmentation of 98% with the mdf file fragmented in 25,000 pieces. Running a standard windows defrag does not resolve this.
Two questions?
1- Is heavy file fragmentation of the MDF file a likely cause of the read queue length bottlneck?
2 - Why is the MDF file not defragmenting? Does the SQL server have to be taken offline? Is it possible to defrag a MDF file?
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Sep 10, 2007
If I return the Average, Minimum, and Maximum values for the counter Physical Disk: Avg. Disk Queue Length, and those values are 10, 0, 87 respectively, which value do I use to compute the Avg. Disk Queue Length for a 4 disk array(RAID 10): Average, Minimum, or Maximum? The disk(lun) is on a SAN.
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Apr 14, 2004
One of my production servers has been determined to be 92% fragmented.
What's the proper procedure for defraging a database server?
I couldn't find anything very helpful in BOL, nor Knowledge Base.
Sidney Ives
Database Administrator
Sentara Healthcare
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Aug 9, 2004
What's the best way to find out if disk fragmentation on Windows 2000 Server is affecting SQL Server performance?
If disk fragmentation is shown to be a cause of performance problems, what are the recommendations for a disk fragmentation strategy? eg. use the win 2000 built in disk defrag utility or buy a 3rd party product like DiskKeeper? How much of an overhead is a product like DiskKeeper that defrags in the background?
Clive
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Jul 23, 2005
If databases on a physical drive [G:] are fragmented, and the drive isextended by adding more hard drives to the array, does it make sense tobackup and restore the fragmented databases?The Windows Server should be able to find contiguous space for eachdatabase, since it shows 75% free space on the SQL Data drive withoutany file fragments on it.Or will it restore to the original location, in which case does it makesense to delete the databases and restore them from the backups?Thank you very much!
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Aug 14, 2007
avg disk queue length is 100%. Any ideas?
=============================
http://www.sqlserverstudy.com
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Nov 8, 2007
Again one client with SAN EMC and again performace is several times worse then you can have with a cheap and primitive IDE drive... :(
Anyway, my question.
I am monitoring many parameters, including Avg Read Queue and Avg Write Queue.
So if I ReadQueue=3 and WriteQueue=7, what does it mean?
Scenario 1, there are 2 different Queues (R- read request, W - write request):
Windows --> Device
Read. Queue: R:R:R
Write Queue: W:W:W:W:W:W:W
Scenario 2:
Windows --> Device
Common Queue: W.R.W.W.R.W.W.R.W.W
In other words, if SQL server flushes writes (TRAN COMMIT or CHECKPOINT), generating hundreds or even thousands of write requests in few milliseconds, so Queue grows to 100-300 for a second or so, are read requests locked during that time?
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Oct 25, 2007
I am running SQL server 2000 SP4 on a server with 2 Dual core 4G processors with data attached via a SAN>
I have a 70G database with 10 users that is giving attrocious performance. I have just tried to run a count(*) accross a couple of tables and am still waiting for the results 15 mins later. When I look at the disk queue it is around 50/60. I thought the target for this was around 2. I am sure that the hardware that we have in place is capable of running this db. However I`m not sure how to fully analyse what is going wrong here.
Any tips would be greatfully received.
Si
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Sep 6, 2007
Hi All,
we have collected perfmon data for a specific lun. Here is the background of the lun. The lun is Raid10 with 4 physical disks. We have problems interpreting the data. In the perfmon counter screen we have a max of 435 and average of 0.512. Can somebody tell us what is that we are missing? Any help is greatly appreciated.
Thanks,
Venkat.
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Jun 16, 2003
Does anyone have any recommendation on whether it's better to monitor the average queue lenght for physical or logical drives? What about for a RAID set?
Just wondering,
thanks
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Jul 17, 2007
PROBLEM: Sporadic spikes in Avg. Disk Queue Length with users freezing up until it comes down.
Server:
-SQL Server 2000 SP4
-Windows Server 2003
-4 Intel Xeon Processors 5130 @ 2.00 GHz
-4 GB of RAM (SQL Configured Dynamically with min. of 0 and max. of 3072)
-Max Worker Threads – 255
Environment:
-100 users with about 65 on Thin Clients going through a Remote Desktop Server
-Front End CRM package is a program called Telescript
-I do not use replication or any triggers, mainly just scheduled DTS packages
-Largest and most heavily used Database is 13Gbs with using a fill factor of 80 on my indexes
Recent Changes – The most notable thing that I changed in the last couple of weeks as this problem arose was the SQL Mail function. I started using that and created some DTS packages that sent out emails. Our user base has been steadily growing, but nothing drastic.
So Far – The buffer cache hit ratio is good and I have not seen any problems with memory so that is ruled out. The processor time never maxes out, but it does appear to double when the Avg. Disk Queue Length spikes. I re-indexed my active tables and performed shrinks over the weekend, but the problem occurred yesterday again. Sometimes it will last under a minute, but the problem is really when it lasts for several minutes. I used SQL Profiler to try and identify what the query was causing the problem, and while I see some large audit times, I cannot tell what the problem is. I had a hard time reading through that with all of the Stored Procedures that were invoked (ie. cursor fetches). The server itself is very new and has only been in use for about 2 months, so I couldn’t imagine it would be hardware fragmentation.
QUESTION: What else should I be looking at or could I use to figure out where this problem is stemming from? I am in a corner and could use any suggestions as to diagnose this problem.
Thanks in advance,
Don
dkoehne@401kexchange.com
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Feb 20, 2001
Hello,
this is my configuration :
1) 3 disks in RAID5 that hold the SQL data
2) 1 disk in RAID0 that holds the only paging file.
What will happen to the SQL data (DB) when the disk that holds the paging file crashes?
Kindest regards,
Luc.
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Aug 5, 2007
I own a DELL dimesnsion 4600 desktop. I purchased it with windows xp HOME although I have upgraded to windows xp professional. I am trying to install Office Enterprise 2007 with the disk i purchased. My computer will not pick it up though. I know the cd works because I tried it on another computer but didnt intsall it. That computer read the disk. My computer will not. any help? desperate need
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Nov 26, 2007
OBJECTIVE: I would like to read a text file from SQL Server 2000, read the text file content, and load its conntents in a RichTextBoxTHINGS I'VE DONE AND HAVE WORKING:1) I've successfully load a text file (ex: textFile.txt) in sql server database table column (with datatype Image) 2) I've also able to load the file using a Handler as below: using System;using System.Web;using System.Data.SqlClient;public class HandlerImage : IHttpHandler {string connectionString;public void ProcessRequest (HttpContext context) {connectionString = System.Configuration.ConfigurationManager.ConnectionStrings["NWS_ScheduleSQL2000"].ConnectionString;int ImageID = Convert.ToInt32(context.Request.QueryString["id"]);SqlConnection myConnection = new SqlConnection(connectionString);string Command = "SELECT [Image], Image_Type FROM Images WHERE Image_Id=@Image_Id";SqlCommand cmd = new SqlCommand(Command, myConnection);cmd.Parameters.Add("@Image_Id", System.Data.SqlDbType.Int).Value = ImageID;SqlDataReader dr;myConnection.Open(); cmd.Prepare(); dr = cmd.ExecuteReader();if (dr.Read()){ //WRITE IMAGE TO THE BROWSERcontext.Response.ContentType = dr["Image_Type"].ToString();context.Response.BinaryWrite((byte[])dr["Image"]);}myConnection.Close();}public bool IsReusable {get {return false;}}}'>'>
<a href='<%# "HandlerDocument.ashx?id=" + Eval("Doc_ID") %>'>File
</a>- Click on this link, I'll be able to download or view the file WHAT I WANT TO DO, BUT HAVE PROBLEM:- I would like to be able to read CONTENT of this file and load it in a string as belowStreamReader SR = new StreamReader()SR = File.Open("File.txt");String contentText = SR.Readline();txtBox.text = contentText;BUT THIS ONLY WORK FOR files in the server.I would like to be able to read FILE CONTENTS from SQL Server.PLEASE HELP. I really appreciate it.
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Dec 28, 2006
hello,all
I am new to Sql 2000,I installed sql 2000 database in C disk,but Now I found my C disk space is smaller than before,So I want to move my databse(include data and structure) from C Disk to D Disk(its space is very large) .
is it possible to do it ?
if its can be done ,do I need to change my asp.net program source code (exp: chaneg my crystal report connectstring ) ?
thanks in advanced!
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Jan 11, 2006
Hello,
This is info that I am still not certain about and I just need to make sure, my gut feeling is correct:
A.
When a procedure is triggered upon reception of a message in a queue, what happens when the procedure fails and rolls back?
1. Message is left on the Queue.
2. is the worker procedure triggered again for the same message by the queue?
3. I am hoping the Queue keeps on triggering workers until it is empty.
My scenario is that my queue reader procedure only reads one message at a time, thus I do not loop to receive many messages.
B.
For my scenario messages are independent and ordering does not matter.
Thus I want to ensure my Queue reader procedures execute simultaneously. Is reading the Top message in one reader somehow blocking the queue for any other reader procedures? I.e. if I have BEGIN TRANSACTION when reading messages of the Queue, is that effectively going prevent many reader procedures working simultaneously. Again, I want to ensure that Service broker is effectively spawning procedures that work simultaneously.
Thank you very much for the time,
Lubomir
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May 13, 2008
Hello Experts,
I am createing one task (user control) in SSIS. I have property grid in my GUI and 2 buttons (OK & Cancle).
PropertyGrid has Properties like SourceConnection, OutputConnection etc....right now I am able to populate Connections in list box next to Source and Output Property.
Now my question to you guys is depending on Source Connection it should read that text file associated with connection manager. After validation it should pick header (first line of text file bases on record type) and write it into new file when task is executed. I have following code for your reference. Please let me know I am going in right direction or not..
What should go here ?
->Under Class A
public override DTSExecResult Execute(Connections connections, VariableDispenser variableDispenser, IDTSComponentEvents componentEvents, IDTSLogging log, object transaction)
{
//Some code to read file and write it into new file
return DTSExecResult.Success;
}
public const string Property_Task = "CustomErrorControl";
public const string Property_SourceConnection = "SourceConnection";
public void LoadFromXML(XmlElement node, IDTSInfoEvents infoEvents)
{
if (node.Name != Property_Task)
{
throw new Exception(String.Format("Invalid task element '{0}' in LoadFromXML.", node.Name));
}
else
{
try
{
_sourceConnectionId = node.Attributes.GetNamedItem(Property_SourceConnection).Value;
}
catch (Exception ex)
{
infoEvents.FireError(0, "LoadFromXML", ex.Message, "", 0);
}
}
}
public void SaveToXML(XmlDocument doc, IDTSInfoEvents infoEvents)
{
try
{
// // Create Task Element
XmlElement taskElement = doc.CreateElement("", Property_Task, "");
doc.AppendChild(taskElement);
// // Save source FileConnection
XmlAttribute sourcefileAttribute = doc.CreateAttribute(Property_SourceConnection);
sourcefileAttribute.Value = _sourceConnectionId;
taskElement.Attributes.Append(sourcefileAttribute);
}
catch (Exception ex)
{
infoEvents.FireError(0, "SaveXML", ex.Message, "", 0);
}
}
In UI Class there is OK Click event.
private void btnOK_Click(object sender, EventArgs e)
{
try
{
_taskHost.Properties[CustomErrorControl.Property_SourceConnection].SetValue(_taskHost, propertyGrid1.Text);
btnOK.DialogResult = DialogResult.OK;
}
catch (Exception ex)
{
Console.WriteLine(ex);
}
#endregion
}
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Jul 2, 2015
I have a filetable that contains a binary file. I need to do a selective read of the file stored in the file table. I can write a C# CLR function that will open the file, read n bytes the from a starting byte. Or I can write a SQL statement that reads the stream in the filetable into a VARBINARY variable using SUBSTRING beginning at the starting byte (offset from 1) for the same n bytes.
Both give me the same result. However, the SQL statement takes considerably longer to read. I know there is overhead in reading through SQL (interpreted language), but the difference in performance is substantial, and I can only attribute this performance degradation if SQL first tries to "load" the entire stream before it identifies the portion of the stream that it needs to read beginning at the starting byte offset.
I wonder if this is the case or if there is another option to read a stream from a filetable directly through SQL queries that is more efficient.
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Sep 28, 1999
Hi,
I am trying to create a scheduled task taht will restore a database from a backup file. I do not store my backups on a backup device, but on a local disk. To restore a DB from a backup device, the following statement will work:
"Load DBName from BackupDeviceName". Does any know what statement to use to restore from a file, if the file is "E:DBName_db_dump_199909272220".
Thanks in a advanced.
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Feb 20, 2004
It's probably a really easy thing to do, but I can't find out how to do it, so hopefully somebody can spare the time to help.
I want to read in T-SQL contained in a file held on disk and execute it in a stored procedure.
Anybody know how to get the contents of the text file into a variable so I can exec it ?
Thanks for your time.
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Feb 20, 2004
It's probably a really easy thing to do, but I can't find out how to do it, so hopefully somebody can spare the time to help.
I want to read in T-SQL contained in a file held on disk and execute it in a stored procedure.
Anybody know how to get the contents of the text file into a variable so I can exec it ?
Thanks for your time.
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Mar 24, 2008
Hi All,
I need to read a csv file, which is in remote server using SQl Bulk Insert Command.
Can I read a file Which is in remote server using BULK INSERT.
Thank you.......
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Feb 21, 2000
I am getting occasional failures of a SQL Server 7.0 complete backup to disk on a production database. The errors seem to indicate that another process has the disk file open at the time of the backup. The errors contain the following texts : -
'Cannot open backup device'
'Operating System Error=32 Process cannot access file because it is being used by another process'.
The only other process that should access the disk file is an ARCserveIT scheduled job to copy the disk backup to tape but this is completing long before.
Any ideas or suggestions?
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Dec 3, 2007
Hi All,
One of the drives that stores the database file is close to running out of space. The chance of me getting more space added to this drive any time soon are really low. What are other options I have?
Thanks.
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Dec 3, 2007
Hi All,
One of the drives that stores the database file is close to running out of space. The chance of me getting more space added to this drive any time soon are really low. What are other options I have?
Thanks.
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Mar 20, 2004
My logfile has grow the disk full - the logfil is 25 gb and I have 4 gb free.
I can't shrink the log fil !
Can I set the log file to null ??
I have backup my datafil successfully!
Help!
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Apr 5, 2004
Hi all,
I have to give support to this new client of ours and the system out there was a real mess.The log files for all four databases were ranging from 5 to 9 GB's, no maintanance no nothing was done since the setup of the system. I have truncated the logs after taking proper backups since it all started after they compalined a DTS was not working, which was due to no disk space available ;).
Now I have to shift the log files to a seperate disk.
I know it can be done by detaching the database and attaching it back, I was wondering if we can do it without bringing the system offline?
Anycomments welcome.
Thankyou.
regards,
harshal.
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Jul 13, 2007
Hi everyone,
Due to running out of disk space and reducing I/O contention, I plan to seperate data files and log files to different disk arrays.
My plan is to
- detach all databases
- copy log files to another disk
- attach all databases
The total size of log files is about 60GB. It becomes a problem becasue it spend too much time passing files. To reduce down time, is there any way I can do?
Can I just create new log files and remove the current files by using sql management studio?
any other suggestions? Thanks in advance
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Apr 7, 2008
Hi,
I'm trying to write a restore script. In the past I've always used the SSMS GUI to restore. When running the script below, the process got stuck at around 90%. Eventually I aborted the restore and found out that my C drive was full. The log file of the database I was restoring was 32GB. Can anyone tell me what I'm doing wrong? Thanks.
Code Snippet
ALTER DATABASE [oms] SET SINGLE_USER WITH ROLLBACK IMMEDIATE
GO
RESTORE DATABASE [oms]
FROM DISK = N'C:Program FilesMicrosoft SQL ServerMSSQL.1MSSQLBackupOMS_Blank_Production.bak'
WITH FILE = 1,
REPLACE,
STATS = 10
GO
ALTER DATABASE [oms] SET MULTI_USER;
GO
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Nov 10, 2006
catcat writes "Hi All,
Our MSSQL 2000 server crashed yesterday and one database cannot be restored. the latest backup we have is june. We can only recover the MDF file from the harddisk and according to our admin, it cannot be restored anymore because no proper shutdown was made.
Will appreciate your help here."
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Oct 4, 2007
Hi all
My Transactional log size increased to 39GB, it is in full recovery mode,
To regain the space, i have done the following
BACKUP LOG DB_NAME WITH TRUNCATE_ONLY
DBCC SHRINK_FILE (LOG_FILE_NAME,500)
But not able to regain the space in the hard disk.
No Transactional backups to truncate the log file were setup.
Can you please tell me why the space was released and what should i do further to clean up the sapce
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Feb 12, 2007
In SQL Server 2005, via the GUI, I wish to backup a database to an additional disk file (there is already an existing backup disk file for this database), so that I can have more than one backup. I've added the new disk file name, highlighted it, and clicked OK.
I get an immediate error (see below). Note, the 2nd error message is specifying the existing backup disk file, not the new one I'm attempting to create.
"Backup failed for Server 'WCS-DEV-TPA'. (Microsoft.SqlServer.Smo)"
"System.Data.SqlClient.SqlError: The volume on device 'D:Program FilesMicrosoft SQL ServerMSSQLBACKUPWCS_ADV_Longmont.bak' is not part of a multiple family media set. BACKUP WITH FORMAT can be used to form a new media set. (Microsoft.SqlServer.Smo)"
Does anyone know what causes this and how to correct it?
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Sep 16, 2015
Do you have to move the entire content of the log folder to the new location?
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