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I noticed that SQL Server has a surprisingly large number of writes to \System Volume Information\{guid1}{guid2}

What is Sql Server doing when something like this happens?

enter image description here

In the above image half of my write IO for sqlsevr.exe is used for the System Volume Information writes.

This is being run in Windows 7 Profressional.


here is the output of vssadmin list shadows

vssadmin 1.1 - Volume Shadow Copy Service administrative command-line tool
(C) Copyright 2001-2005 Microsoft Corp.

Writer name: 'Task Scheduler Writer'
   Writer Id: {d61d61c8-d73a-4eee-8cdd-f6f9786b7124}
   Writer Instance Id: {1bddd48e-5052-49db-9b07-b96f96727e6b}
   State: [1] Stable
   Last error: No error

Writer name: 'VSS Metadata Store Writer'
   Writer Id: {75dfb225-e2e4-4d39-9ac9-ffaff65ddf06}
   Writer Instance Id: {088e7a7d-09a8-4cc6-a609-ad90e75ddc93}
   State: [1] Stable
   Last error: No error

Writer name: 'Performance Counters Writer'
   Writer Id: {0bada1de-01a9-4625-8278-69e735f39dd2}
   Writer Instance Id: {f0086dda-9efc-47c5-8eb6-a944c3d09381}
   State: [1] Stable
   Last error: No error

Writer name: 'ASR Writer'
   Writer Id: {be000cbe-11fe-4426-9c58-531aa6355fc4}
   Writer Instance Id: {6584bb82-094c-4896-9be2-880ff9fb4d80}
   State: [1] Stable
   Last error: No error

Writer name: 'System Writer'
   Writer Id: {e8132975-6f93-4464-a53e-1050253ae220}
   Writer Instance Id: {669bba38-6066-4bf6-99af-8d312f66648d}
   State: [5] Waiting for completion
   Last error: No error

Writer name: 'SqlServerWriter'
   Writer Id: {a65faa63-5ea8-4ebc-9dbd-a0c4db26912a}
   Writer Instance Id: {48de0d7f-b7a0-457e-8bab-fefe2089286e}
   State: [1] Stable
   Last error: No error

Writer name: 'MSSearch Service Writer'
   Writer Id: {cd3f2362-8bef-46c7-9181-d62844cdc0b2}
   Writer Instance Id: {d5c4ab16-b67e-4476-976b-4dba610084d8}
   State: [5] Waiting for completion
   Last error: No error

Writer name: 'WMI Writer'
   Writer Id: {a6ad56c2-b509-4e6c-bb19-49d8f43532f0}
   Writer Instance Id: {5e334911-6049-4d29-8d33-d9b230b46ec2}
   State: [5] Waiting for completion
   Last error: No error

Writer name: 'COM+ REGDB Writer'
   Writer Id: {542da469-d3e1-473c-9f4f-7847f01fc64f}
   Writer Instance Id: {e9dde2da-5cee-4d65-ac50-45387be4b600}
   State: [1] Stable
   Last error: No error

Writer name: 'Registry Writer'
   Writer Id: {afbab4a2-367d-4d15-a586-71dbb18f8485}
   Writer Instance Id: {9825b95f-94a0-438b-a359-4111aa308a60}
   State: [1] Stable
   Last error: No error

Writer name: 'BITS Writer'
   Writer Id: {4969d978-be47-48b0-b100-f328f07ac1e0}
   Writer Instance Id: {d23d67d3-c421-4e9a-9965-123ec802bfcc}
   State: [1] Stable
   Last error: No error

Here is the output of vssout list shadows (too long to post here)

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4 Answers 4

up vote 3 down vote accepted

It's Windows doing shadow copies of your E-drive.

(This is not normal to use on data/log drives for SQL server, it increases I/O tremendously).

Edit: Or, well.. atleast schedule it to something sane, like one hour before everyone comes to work.

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This also happens with my C drive when I was using a database on C. Where would I go to shut it off/change the scheduelling. –  Scott Chamberlain Sep 15 '11 at 18:25
    
Right-click on the drive, select properties. There is a "Shadow Copies" tab. –  pauska Sep 15 '11 at 18:26
    
I am on Windows 7 Professional, I do not have a Shadow Copies tab. The only thing I can think of is the Previous Version tab but I can only turn it on and off, there is no way to schedule it. –  Scott Chamberlain Sep 15 '11 at 18:31
    
Running SQL server on Windows 7?.. Oh well, there is no way to modify how it works - you can only disable it completely by disabling the shadow copy service. Be aware that you'll lose important snapshots when doing windows update etc. –  pauska Sep 15 '11 at 18:40
    
@Scott - also, if you're running SQL server on Windows 7, it would have been a good idea to put that info into your question. From the FAQ, this site is for systems admins working on things that would generally be called production systems - that excludes personal desktop issues, unless it's related to managing lots of desktops. –  mfinni Sep 15 '11 at 18:51
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Smells like VSS snapshots.

Do you have software (probably backups) telling SQL Server to create VSS snaps?

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Where would I go to check? –  Scott Chamberlain Sep 15 '11 at 18:22
    
Check what you've got in vssadmin list writers and vssadmin list shadows –  Shane Madden Sep 15 '11 at 18:26
    
(you'll need to run those commands in a command prompt that's been started as administrator) –  Shane Madden Sep 15 '11 at 18:34
    
I did, now its a matter of decoding what it returning. VSS is something I have never worked with before. –  Scott Chamberlain Sep 15 '11 at 18:36
    
I updated my original post with the output of the two commands, I do not know what I am looking for so I know what to disable. –  Scott Chamberlain Sep 15 '11 at 18:43
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My guess is that you're doing a backup of the server itself, or a backup of the SQL Server databases with a VSS aware backup program (Windows Backup, SQL Maintenance Plan or SQL database backup job, or third party VSS aware backup software).

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You can also disable shadow copy on the folder of your database's files: http://msdn.microsoft.com/en-us/library/aa819132(v=vs.85).aspx

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