Restoring with multiple BAK-files (with multiple CPU-cores)

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Restoring with multiple BAK-files (with multiple CPU-cores)

gkramer 23701

Ten Centuries

Points: 1381
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December 6, 2018 at 8:00 am

#409363

Hi all,
I do have a question about restoring databases:

SQL server uses just on CPU-core when performing a regular backup to 1 BAK file.
When restoring this BAK file SQL server uses just one CPU-core.
Is it possible to direct multiple CPU-cores to the backup mechanism to performing a backup to multiple files - and is this (addressing multiple CPU-cores) also possible when restoring the multiple BAK files to one database?
Our backup (2,5 TB – compressed 500 GB) takes about 4-5 hours to restore and I like to speed this up. Is this a possible solution or are there other ways to accomplish this?
All replies are welcome.
Regards
Guus Kramer
The Netherlands

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Jeff Moden SSC Guru Points: 1003853 More actions · Answer 1

Do you have the Standard or Enterprise edition of SQL Server?

Also, spitting the backups to multiple files could actually slow things down unless you can guarantee that each file will be saved on totally separate dedicated spindles. That's not the case in most systems anymore.

Finally, CPU isn't the limiting factor here. Disk Reads, Disk Writes, size of the "pipe", and configurations such as "Instant File Initialization" and packet size are.

Of course , one good experiment is worth a thousand expert opinions and hours of research. Try the multiple file thing. I think you'll be disappointed but the experiment will remove or confirm any doubts for your particular setup.

--Jeff Moden

RBAR is pronounced "ree-bar" and is a "Modenism" for Row-By-Agonizing-Row.
First step towards the paradigm shift of writing Set Based code:
________Stop thinking about what you want to do to a ROW... think, instead, of what you want to do to a COLUMN.

Change is inevitable... Change for the better is not.

Helpful Links:
How to post code problems
How to Post Performance Problems
Create a Tally Function (fnTally)

gkramer 23701 Ten Centuries Points: 1381 More actions · Answer 2

gkramer 23701

Ten Centuries

Points: 1381

December 6, 2018 at 8:17 am

#2015664

Enterprise edition

goher2000 SSCertifiable Points: 5479 More actions · Answer 3

in my experience, disk is bottleneck most of the time, try it out.

SET NOCOUNT ON
declare
@fno int,
@dbname varchar(100),
@path varchar(100),
@finame varchar(100),
@dsk varchar(1000),
@ts VARCHAR(1000)
begin
set @fno = 64
set @dbname ='mydb'
set @path ='y:\backup\' + CAST(@@servername AS VARCHAR) +'\'

SET @finame = REPLACE(@dbname,' ','_')
SELECT @ts='_' +replace(replace(replace(CONVERT(VARCHAR(20),GETDATE(),120),':','_'),'-',''),' ','_') + '_FILENO_'
print 'Backup Database [' + @dbname + '] to '
--print @fno
    while @fno > 1
    BEGIN
        --SELECT 'this is test'
    SET @dsk= 'disk = ' +CHAR(39) + @path + @finame + @ts + cast(@fno as varchar) + '.full' + CHAR(39) + ','
    PRINT @dsk
    set @fno = @fno - 1
    END
--PRINT 'out of loop'
SET @dsk= 'disk = ' +CHAR(39) + @path + @finame + @ts + cast(@fno as varchar) + '.full' + CHAR(39)
    PRINT @dsk + ' with compression'

end

Jeff Moden SSC Guru Points: 1003853 More actions · Answer 4

gkramer 23701 - Thursday, December 6, 2018 8:17 AM
Enterprise edition

In that case, if you're not using compression, you should give it a try. I did a (actually, multiple times this past weekend on a test box) restore of a 2.2TB database in 55 minutes. Of course, I also have some other tricks of the trade going on like "Instant File Initialization" (IFI) and defining both the packet and buffer size in the RESTORE command. I also have a giga bit connection between me and the location of the backup but most of the performance comes from using compression during the backup and having IFI active.

--Jeff Moden

RBAR is pronounced "ree-bar" and is a "Modenism" for Row-By-Agonizing-Row.
First step towards the paradigm shift of writing Set Based code:
________Stop thinking about what you want to do to a ROW... think, instead, of what you want to do to a COLUMN.

Change is inevitable... Change for the better is not.

Helpful Links:
How to post code problems
How to Post Performance Problems
Create a Tally Function (fnTally)