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backups

Improved Laziness

I’m really digging Powershell the more that I work with it.  It’s nice to have so much rich functionality within the operating system and not having to fuss with compilers or syntax.  One of my more recent projects was automated restore testing for our servers.  Now, while I won’t be showing that to you (yet), working with that script got me more time with the SMO.

The SMO is incredibly powerful.  You have so much functionality that it can be a little overwhelming.  There’s also a lot of stuff you can do in the SMO that you can also do in standard T-SQL.  As with anything, it’s a matter of using the right tool.  I’m finding that what makes Powershell the right tool is it’s ability to work outside of the database, avoiding some of the restrictions placed (rightly so) on the engine and how it interacts with the OS.  It makes Powershell ideal for things like file manipulation and talking with the OS.  It also gave me a slightly cleaner way to generate restore scripts.

If you have seen my previous restore building script, it was handy that it worked in T-SQL, but because it had no visibilty into the file system, I had no real way to logically combine fulls, diffs, and transaction logs to build a single script.  Sure, I could probably assemble something looking at msdb.dbo.backupset, but that only works if I’ve got access to the server the backups were done on.  By leveraging Powershell and the SMO, I can now read the file system, interogate each backup file to see that it fits in the LSN sequence, and build out a SQL script.

The steps are simple:

  1. Point the script at a target directory where all the backup files live and a SQL instance that has access to the file directory (typically, this is the instance you’ll run the restore on).  You can also declare a database name (if you want something different) and an output directory (which will otherwise default to your My Documents folder).
  2. The script will then use the SMO to read in the backup files, coordinating the LSNs to order them properly for the restore.
  3. The entire restore script will be written to the output directory.

Some caveats:

  • The script identifies files based on extension (.bak for Full, .dff for Differential, and .trn for Transaction Log).  This is based on how I write out my backup files, so this is the key piece of logic that will need to be altered to make this more generic.
  • The full restore will “move” the files to their original location.  If restoring to a different server, you’ll want to alter these file locations.

Now, I’m by no means a Powershell guru, but I do like making my life easier through scripting.  There’s probably more elegant ways to do this, but it’s clean enough for my purposes.  Hopefully in makes your life easier too!

(Feel free to download the script here.)

<#
.SYNOPSIS
Builds Database Restore script, coordinating Full, Diff, and Log backups.
.DESCRIPTION
Generates a database restore .sql script for restoring a database.
Mike Fal (htp://www.mikefal.net) 2012-07-09
.PARAMETER
String
    dir(REQUIRED) - Target directory where backup files reside
    server(REQUIRED) - Target server restore used by SMO to build restore script.  Should be server you want to restore to.
    database - Database name to restore. If blank, database name from the backup will be used.
    outputdir - Output directory for script.  If empty, user's My Documents will be used.
.EXAMPLE
    .\Build-Restore.ps1 -dir "C:\database_backups" -server "localhost"
.NOTES
    Script acquires files based on extension:
        .bak = Full
        .dff = Differential
        .trn = Transaction log
#>
param([parameter(Mandatory=$true)][string] $dir,
      [parameter(Mandatory=$true)][string] $server,
      [string] $database,
      [string] $outputdir=([Environment]::GetFolderPath("MyDocuments")))

#load assemblies
[System.Reflection.Assembly]::LoadWithPartialName('Microsoft.SqlServer.SMO') | out-null
[System.Reflection.Assembly]::LoadWithPartialName("Microsoft.SqlServer.SmoExtended") | Out-Null

#processing functions
function Get-Restore{
    Param($db,
          $backupfile)

    $rs=new-object("Microsoft.SqlServer.Management.Smo.Restore")
    $rs.Devices.AddDevice($backupfile.FullName, "File")
    $rs.Database=$db
    $rs.NoRecovery=$true
    $rs.Action="Database"

    return $rs
}#Get-Restore

function Get-Header{
    Param($rs,$srv)

    $dt=$restore.ReadBackupHeader($srv)
    return $dt.Rows[0]
}#Get-Header

#START SCRIPT
$sqlout = @()
$smosrv = new-object ('Microsoft.SqlServer.Management.Smo.Server') $server

$full = gci $dir | where {$_.name -like "*.bak"} | Sort-Object LastWriteTime -desc | Select-Object -first 1
$diff = gci $dir | where {$_.name -like "*.dff"} | sort-object LastWriteTime -desc | select-object -first 1
$trns = gci $dir | where {$_.name -like "*.trn"} | sort-object LastWriteTime

#initialize and process full backup
$restore=Get-Restore $database $full
$hfull=Get-Header $restore $smosrv
if($database.Length -eq 0)
{
    $database=$hfull.DatabaseName
    $restore.Database=$database
}

$LSNCheck=$hfull.FirstLSN
$files=$restore.ReadFileList($smosrv)
foreach($file in $files){
        $newfile = New-Object("Microsoft.SqlServer.Management.Smo.RelocateFile") ($file.LogicalName,$file.PhysicalName)
        $restore.RelocateFiles.Add($newfile) | out-null
}

$sqlout+="/****************************************************"
$sqlout+="Restore Database Script Generated $(Get-Date)"
$sqlout+="Database: "+$database
$sqlout+="****************************************************/"
$sqlout+="--FULL RESTORE"
$sqlout+=$restore.Script($smosrv)

#process differential backups
if($diff -ne $null){
    $restore=Get-Restore $database $diff
    $hdiff=Get-Header $restore $smosrv

    if($hdiff.DifferentialBaseLSN -eq $LSNCheck){
        $sqlout+="--DIFF RESTORE"
        $sqlout+=$restore.Script($smosrv)
        $LSNCheck = $hdiff.LastLSN
    }
    else{
        $LSNCheck = $hfull.LastLSN
    }
}

#process transaction log backups
if($trns -ne $null){
    $sqlout+="--TRN LOG RESTORE"

    foreach ($trn in $trns){
        $restore=Get-Restore $database $trn
        $htrn=Get-Header $restore $smosrv
        if($htrn.FirstLSN -le $LSNCheck -and $htrn.LastLSN -ge $LSNCheck){
            $sqlout+=$restore.Script($smosrv)
            $LSNCheck = $htrn.LastLSN
        }
    }
}

#Write final recovery line
$sqlout+=&quot;<code>r</code>n&quot;
$sqlout+=&quot;--COMPLETE RESTORE/ONLINE DB&quot;
$sqlout+=&quot;RESTORE DATABASE &quot;+$database+&quot; WITH RECOVERY&quot;

#output script file
$sqlout | Out-File &quot;$outputdir\restore_$database.sql&quot;

Survival Monitoring

The IT world is a jungle. Countless threats lurk like predators, ready to devour us if we’re not careful. Seemingly benign events can quickly turn in to raging panic fests and danger lives everywhere that we’re not looking. To survive you need to be prepared and proactive. Unfortunately, many of us are thrown into this with little more than a pat on the back and a smile, as if we just got dropped out of a helicopter into the African jungle with little more than a pack of chewing gum and a pocket knife. Yet, we need to survive not just the next day, but the weeks and months ahead of us.

Because we need to survive, there’s some basic stuff we need to focus on in order to ensure our survival. It’s not everything we need to live happy, contented careers, but the minimum elements we need to watch in our environments to make sure we live to see the next day. If we were trapped in the wilderness, we’d first focus on shelter, fire, and food. In database terms, we need to first keep an eye on backups, services, and disk space if we want to make it to the next day.

Shelter from the storm

The most important item in a DBA’s life is backups. We can have screaming disk, tons of CPU, and all sorts of clustering, but that means nothing if our files get corrupted or the building burns down. Just like shelter in the wilderness is a place where we can always find protection, our database backups will always give us something to recover to.

Keep an eye on three things when it comes to your backups. First, make sure they’re actually occurring. Look to the backupset table in msdb for this, because it will tell you exactly when your backups are occurring, whether they’re log backups, fulls, or differentials. Next, where are your backups located? Backups won’t do much for you if they’re stored to the local computer and then that computer’s hard drive burns up or gets corrupted. Make sure that your backup files get to another location. Finally, make sure your backups work. Just because you take a backup doesn’t always mean that backup is reliable. Perform restores when it’s not an emergency to validate your backups, so you’ll know things will work when it’s an emergency.

Backups are your safety net. No matter what else happens, you should always have them to fall back on. It may not be pretty, but you’ll be glad they’re there when you need them.

Give me fuel, give me fire

Fire gives us the energy to get things done, whether it’s keeping us warm or being used to cook food. This is the same with your SQL Server services. If these aren’t running, your databases are down and your company is losing money. We can’t always prevent the interruption, but we need to be ready to respond when that interruption occurs. As DBAs we need to be proactive and watch our services.

Also, we can’t limit this just to the SQL Server database service. How many of you run SQL Agent jobs to perform your backups and maintenance? I know I do. If the Agent service is down, the databases will be working fine, but none of that other work is getting done. To boot, you probably won’t be getting any notifications about these jobs not running, so this will be one big blind spot.

We can’t take on faith that services will start automatically. Sometimes they stop for completely legitimate reasons. It’s our job to make sure they’re up and running and very few things are worse than that surprise call about something not running because a SQL related service is down (one thing that is worse is that we don’t have a backup, see above). Watch your services and you’ll sleep better and warmer.

How can you have any pudding if you don’t eat your meat?!

People got to eat. Once we have a place to sleep and fire to keep us warm, this is the next thing that we need to keep us going. For databases, this food is disk space. We could expand it out to CPU and RAM, but I’ve seen many a server that will limp along when these are consumed and stop stone cold when a file can’t grow anymore because the server ran out of space. If we want a happy database, we need to keep our database fed.

Primarily, watch the free space on your drives (wherever your files are stored), but also keep an eye on the free space within your files. You need to know when your files are going to grow and consume your space. The immediate survival goal is to make sure your server has enough disk to keep running, but you also need to monitor how that disk is getting so that you can be ready to add disk as necessary.

Getting by

Please note, doing all of the above doesn’t guarantee that your server will hum along happily. This isn’t happiness, this is survival. This is the bare minimum you want to do to ensure your company’s service and data. That’s the thing about monitoring: there are hundreds of counters and statistics you can watch, it’s up to you to figure out which of those are important. That’s why you want to start with the fundamentals first, or you could be putting your data, your job, and your company at risk.

I wanted to start with the overview of this strategy. Stay tuned my next post (might be next week or next Thursday, depends on my schedule), I will actually cover some technical solutions to this monitoring, some SQL and PowerShell scripts you can use to keep an eye on all of the above. If you want to get a head start, take a look at my post on backupset or look at Brent Ozar’s(b|t) sp_blitz.

 

T-SQL Tuesday(#tsql2sday) #26 – Lazy Restore Commands

I missed out on T-SQL Tuesday #25 (Tips ‘n Tricks) on the first go around, so I’m glad that with #26 I get another crack at it. Mine is pretty simple, but has saved me a lot of time when doing database restores. Whether I’m getting a database back online or (more likely) moving a database to another instance, I don’t want to be bothered for digging around to get my restore going.

As a DBA, I am two things:

  1. I hate using the GUI. Clicking through countless windows is for the birds and I would much rather type three commands than click ‘Next’ three times.
  2. I’m lazy. So those three commands? I write them once and save ‘em to a file so I can run them over and over and over….etc. Automation FTW!

So, restores. We all do them and they can get irritating. I know one of the most annoying things is relocating the files with MOVE when you’re bringing the database up on a different server. This is why a lot of folks use the GUI, because SQL Server can handle that behind the scenes and, if you really want, you can script it out. Well I’ve got another way.

You know you can RESTORE WITH FILELIST to get the database files within a backup. Why not take that a step further and capture it in a table? Then, once it’s in a table, we can use a little bit of SQL coding to give us a template to generate our restore command. Take a look:

--Turn off annoying rowcount
SET NOCOUNT ON

--Some variables
declare @v_restore varchar(1000)
declare @v_backup varchar(1000)
declare @v_sql varchar(max)
declare @datadir varchar(1000)
declare @logdir varchar(1000)

--Set backup file location, database name
set @v_backup = 'C:\demo\test.bak'
set @v_restore='Test_demo'
set @datadir = 'C:\Restore\Data'
set @logdir = 'C:\Restore\Log'

--Storage table

declare @restorelist table
(LogicalName nvarchar(128)
,PhysicalName nvarchar(260)
,Type char(1)
,FileGroupName nvarchar(128)
,Size numeric(20,0)
,MaxSize numeric(20,0)
,Fileid tinyint
,CreateLSN numeric(25,0)
,DropLSN numeric(25, 0)
,UniqueID uniqueidentifier
,ReadOnlyLSN numeric(25,0)
,ReadWriteLSN numeric(25,0)
,BackupSizeInBytes bigint
,SourceBlocSize int
,FileGroupId int
,LogGroupGUID uniqueidentifier
,DifferentialBaseLSN numeric(25,0)
,DifferentialBaseGUID uniqueidentifier
,IsReadOnly bit
,IsPresent bit
,TDEThumbprint varchar(100)) –-Be careful, this last field (TDEThumbprint) isn’t in 2k5

--Capture the file list
insert into @restorelist
exec('RESTORE FILELISTONLY FROM DISK='''+@v_backup+'''')

--Build your restore command
select @v_sql = 'RESTORE DATABASE '+@v_restore+' '+char(10)+'FROM DISK=''' +@v_backup+ ''''+ CHAR(10)+'WITH '
select @v_sql = coalesce(@v_sql,'')+'MOVE '''+logicalname +
''' TO '''+CASE when type='L' then @logdir else @datadir end +'\'+ right(physicalname,charindex('\',reverse(physicalname))-1)+''',' + char(10)
from @restorelist

--display the restore command, trim trailing comma and char(10)
print substring(@v_sql,1,LEN(@v_sql)-2)

So that’s a lot of stuff! Well, not really. If you look at it, most of the script is taken up defining the file list table. Change your variables at the top, run the script, and copy the output into another window…BAM! There’s your restore command. And if it’s not perfect, you only need to make one or two changes to the output to clean it up.

This is not the only sproc output you can capture. The biggest lesson from this trick is you should think about other system stored procedures and look for opportunities where you can grab outputs to make your life easier. Help yourself look like a hero and get more sleep by taking advantage of what’s in SQL.

Thanks to Dave Howard(b|t) for offering folks a second chance to share for T-SQL #26!

Brushing up on your (backup) history

Backups are huge, right? As administrators, they should never be far from our minds. Backups are one of the cornerstones of disaster recovery and safeguarding our data. It only makes sense that we want to keep an eye on when backups happen and if they’re successful. Recently, I’ve been making a lot of use of a simple little query that shows me how my backups are doing:

SELECT
  database_name,
  type,
  max(backup_start_date) last_backup
FROM
  msdb.dbo.backupset
GROUP BY
  database_name,
  type

Yes, this is a VERY straightforward query, no hidden magic here. But with this one little SELECT statement, I have been able to quickly establish if my backups are getting run, what specific databases may have problems, and where I need to focus my troubleshooting. By breaking it down by database and type, I am also able determine whether or not my log backups are running (key to out of control log growth), if I’m properly maintaining my recovery chain, and what backups are going to be necessary to restore my database.

Unlocking the secrets

The key is the the backupset table in msdb. This table stores the history of all successful backup operations on the server(emphasis on successful). It’s not just native SQL backups, but those by third party tools as well, so we can have insight in to any backups (or lack of) that are happening. I first came across this table working with Brent Ozar’s(b|t) Blitz script. Brent introduces this query as part of his server take over to establish whether or not your backups are being taken, which is the primary reason I check it. Backing up our data is vital and not doing this would probably be an RGE. If nothing else, this table says “Hey dummy, I need you to look at something!”

If we dig in a little more, though, we can find other useful information. Take the backup_start_date and backup_finish_date fields. By using another simple query, we can then see how our backups perform over time:

SELECT
  database_name,
  backup_start_date,
  datediff(mi,backup_start_date,backup_finish_date) backup_duration,
  backup_size/(datediff(mi,backup_start_date,backup_finish_date)+1) bytes_per_minute
FROM
  msdb.dbo.backupset

Backup duration is a handy metric for base-lining our systems. After all, if our backups start taking longer and longer, it could be an indication of resource contention. If we’re backing up to local disk, we could be choking our throughput. If we’re backing up to a network share, we could be seeing increased bandwidth usage. Also, our databases could just be getting bigger and might require more resources to support them. By including the backup_size field, we can see if longer backups are the result of simply backing up more data or if there might be something else to it.

If we use the backup_size field and its sibling, the compressed_backup_size field, we can gain some additional insights. Since backups will grow in relation to how much the database grows, this gives us a quick and dirty way to report on those growth patterns. Ideally, you’d want to be track the actual database size, but if you don’t have something to capture that historically, this will work in a pinch. Additionally, by combining it with the compressed backup size, you can get an idea of how much space you’re saving if you use the WITH COMPRESSION option in SQL 2008. A quick gotcha here: This will not show the benefits of compression using third party backup tools. Both fields will show the fully compressed backup size if you’re using something like Red Gate SQL Backup, Quest LiteSpeed, or Idera’s SQL Safe.

Cleaning up after yourself

Now not everything with this table is sunshine and rainbows. Maintaining this history is one of the more commonly overlooked areas of SQL Server administration. Ever wonder why your msdb database keeps growing and growing over time? Bingo, it’s because your backupset table keeps increasing with all the additional history stored inside it. What you want to do is schedule a regular run of sp_delete_backuphistory to keep your history to a relevant period. What that time frame is depends on your database size and needs, though I personally go with 90 days as my default.

Those who don’t learn from history…

Successful database administrators are the ones who make monitoring a part of their practice. With it, we can be proactive with our systems and solve problems before they occur. The great thing about the backupset table is that it’s a very easy way to start checking up on your instances, leveraging information that is already a part of the SQL Server core functionality. You don’t need any fancy tools or complex systems, just a few basic queries to get started understanding how your servers, databases, and systems perform on a day to day basis.