block level vs. file level

yip459
yip459 used Ask the Experts™
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Could someone give (or reference a source) that explains  the difference between block level and file level storage of data, in simplest possible terms?
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Guy Hengel [angelIII / a3]Billing Engineer
Most Valuable Expert 2014
Top Expert 2009

Commented:
in short: 1 file is stored using 1 or more blocks (depending on the size).
when doing a incremental or differential backup, when a file has changed, you can do
* a full file backup (all the blocks of the file)
* a backup of just the blocks that have changed ...

this is a good backup "compression" method if you have large files which don't change all at once, but only partially.
Block level backup is normaly usined in a image backup where the entire partition is backed up as one file compared to a file backup where each file is backed up one at a time. Both have their pros and cons.

We use Backup Exec for all server backups and Windows Backup for workstations.

File backups are normally more flexible as you can restore a single file. Image backups normally only allow the entire partition restore. Frommy experience with apps like Ghost yers ago, they normally perform Image backups.
Windows?  Windows Server 2003 and before did file backups with NT Backup.  Windows Server 2008 and after do block level backups with wbadmin, fronted by a wizard.  Both will allow you to restore one or more files, and since Server 2008 R2 you have the option of selecting files.  You can also exclude files and folders.  

NTbackup had this "incremental" or "differential" variations, which I won't attempt to explain here.  Wbadmin does something similiar, but it is invisable.  It compares the prior bits on the backup target with the current bits on the source and only copies the changed ones.  So "incremental" backups with Server 2008 and later are usually very fast and can be done several times during an average work day.  (Shadow Copies, another topic for another time.)
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Paul SolovyovskySenior IT Advisor
Top Expert 2008

Commented:
When most people talk about file or block they do this in terms of storage.  File level is just that, it's accessed as file.  The protocol that is typically used is NFS/CIFS (SMB windows NTFS,etc.).  Normally access for file is a NAS type of device

Block is the underlying storage and is accessed via Fibre Channel, iSCSI, Fibre Channel over Ethernet, etc..  Block storage is typically accessed via direct storage such as  an volume from a disk array or a LUN from a SAN device.

What are you trying to implement or looking into?

Author

Commented:
Just trying to implement some NAS storage, it gives the option to utilize block level or file level , and I needed more infomation about it in order to decide: Thanks all, very informative and you have all helped.
Paul SolovyovskySenior IT Advisor
Top Expert 2008

Commented:
file level means that it can do cifs or nfs.  block level means that it can create a iscsi lun that youc an attach to a server as a volume

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