Differential Back-up on USB-Drive, Mount Failed

[RPN]

Hello Everyone,

I'm actually encountering issues in a differntial back-up on usb drive.

We altern 2 discs on Monday to Thursday in back-uping with differencial way and then a Complete Bac-up each Friday.

Complete back-up is every week succesfull

But each day from Monday to Thurday, the differencial back-up is aborted because this message :

Montage de lecteurs et de supports demandé : 23/07/2013 20:00:02

Aucun support à ajouter n'a pu être monté.

V-79-57344-33037 - Erreur - Échec du montage.

Support de la bandothèque de volume physique introuvable.

Which is, in English, the equivalent to 

No appendable media could be mounted.
V-79-57344-33037 - Error - Mount failed.
Physical Volume Library Media not found.

Note that Supports are configured with 3 hours overwrite protection and Infinite - Allowed append.

I do not understand why it fails :(

[Jaydeep_S]

This is mostly as the Full backup is not accessable. For a lot of things, like GRT, Backup Exec needs the Full and Differential to be able to catalog the GRT view.

[RPN]

Thank you for your fast answer.

Please note that before asking differential back-up, a full back-up has been done on every disc.

So when we insert a week-disc and asking a differential bac-up, it always has a complete back-up inside.

[Jaydeep_S]

RPN, I am not sure if I understand this correctly. I assumed from your original post that you change the disk on Monday and Friday, so it looks something like this.

Full backups on Friday (Disk 1)

Differential on Monday - thursday. (Disk 2)

For when the differential backups run, the Full backup data which is on Disk 1 is not present and accessable by Backup Exec. Am I correct in this.

[RPN]

Almost :)

Full backups on Friday

Differential on Monday - Thursday based excluvely on their first complete Back-up done on each disk some times ago now.

Is there something a understood in a wrong way ?

[Jaydeep_S]

What I am trying to point out here is when you run the differental backups, they are not able to find the Full backups on the disk. This is what could be the problem.

Try to see if there is a way if you can have oth the disks (the one for Full and the one for differential) available when the differential runs.

Or to test this, if you have space on the Full backup disk, try and run a differential on the same disk.

[pkh]

What I am trying to point out here is when you run the differental backups, they are not able to find the Full backups on the disk. This is what could be the problem.

Why is this a problem?  When a differential backup is taken, there is no need to reference the backup set from the full backup.

[pkh]

@RPN - Have you checked that the B2D folder is online BEFORE the start of the job?  Also, check that there are sufficient space on your disk for your differential backup.

BTW, it is not recommended that you append to disk media.  Doing so would not give you any advantage and it only prolongs the media protection period.  You should also set your jobs to overwrite disk media.

[Jaydeep_S]

This would be an issue, if he has some GRT enabled backup application being backed up in the job. The Differntial/Incremental will try to look for the Full backup set to be able to produce the catalogs. That is what I tried to confirm in my very first post.

[Colin_Weaver]

It is a potential problem with things like VMware snapshot images and generating the GRT information. Basically generating the GRT catalogs and other metadata information on VMware backups may need to mount the full and differential backup at the same time. The GRT restore will also need both at the same time. I am not sure if this is more likely to affect Application GRT backups with VMware, although it is possible as we have to mount the VM backup and then within that mount the application data as a secondary mount.

Incrementals  will also be affacted, and it is also possible that other GRT aware backup types might also need the chain to be online.

If it was just a file system standard, traditional agent backup then yes you can run the differential backups without the full (although in Windows 2012 because of the synthetic view of restore selections it's possible a restore would  still need the full chain online, unless you are very careful how you select your files for restore)

[pkh]

If the chain is required for VMware GRT backups, then what happen if the backups are all to tape? How is the chain mounted?

[Colin_Weaver]

If you select a VMWare GRT differential restore from tape then the restore recovers the differential and full to the staging area and then mounts the content to get at the files

If you try to restore a complete VM from a differential on tape, then the recover writes the differential into an empty VMware snapshot directly, then repeats this with the full before using a VMware API command to assemble the two recoverd snapshots into one system

[pkh]

I can understand the situation during a restore.

In your previous answer, you said that the full backup is needed to generate the GRT information when doing a differential GRT backup.  What I am asking is what happens when both the full and differential backups are to tape.  How is the differential backup going to reference the full backup in this case?

[Colin_Weaver]

Whilst I can't really go into full details the Catalog process When going to tape instead of disk  (with or without application GRT) the catalog process is a completely different process, with the main reasons it is different related to the speed and paralllel vs serial access of tape vs disk as a storage medium. Basically Tape backup relies on lot more on a slower mechanism involving accessing the source directly in the VMware environment (and for App GRT the remote agent inside the VM comes into play as well)

Please also bear in mind that unlike a normal backup a VMware backup with GRT enabled has to create 2 sets of Catalogs, one for the capability to backup and restore the VM as a VM, and one for the GRT information (which again if multiple application and file system GRT are in the mix may also mean multiple catalog sets)

[RPN]

Thank you everybody for your answers

@Jaydeep & @Colin

It's mostly standarts file system and, mainly, this is just the transposition of an old system with band/tape that runned correctly.

@PKH

What do you mean ? Usb drive is correctly mouted and accessible and i can see the support into my peripheral.

However, I dicovered something :

- after the work fails, when i go back to "peripheral", i can see that my peripheral/folder E:/ is "Offline" with a red cross on it (it wasn't like this before the rask)

- I click on "Online" again, then go back to the task and do it again, and now it's runnig correctly.

---> It seems that the task always fails the first "try" and then put the "folder" in offline mode. Do do it, I must manually put online the folder again and manually try again..

Where could the issue comes from ?

In anyway, thank you all, you're incredibly fast and sharp.

[Colin_Weaver]

Hmm if no GRT is involved and it is just a traditional remote agent backups then you should NOT need the full mounted to do a differential backup (although if running BE 2012 might need it for a differential restore due to the Synthetic View in 2012)

If this is your scenario then I think you need to log a formal support case for us to look into it further. EDIT especially if your USB disk is going offline in the middle of the backup for no apparent reason

Just as one extra point about the VMware discussion (for others that read this thread) VMware backups are block level backups, as such if a large file only changes some of its blocks then the differential snapshot in VMware will only backup those blocks and not the whole file. Hence various capabilitities need access to the full to correctly be able to take actions on individual files within the VM backup set later. Most other areas of Backup Exec do file level backups so if any part of a file changes the whole file is backed up and obviously means individual actiosn within the backup set may not need the full.

[pkh]

Usb drive is correctly mouted and accessible

Sometimes the USB drive may be detected by Windows, but in BE, the B2D folder on it still shows as offline.  You got to go to the Devices tab and make sure that the B2D folder is online.

[RPN]

@PKH @Collin

It's a bit different, because just before the backup, peripheral appears as online and OK

When attacking the back-up, it immediately stops, reproting error, and then the peripheral appears to offline.

Then i turn online agin the peripheral and launch manually this time the backup, all is OK.

Where does the issue could comes from ?

Anyway, thank you all for this great support, quite rare.

[pkh]

Test your external harddisk with this utility

B2Dtest.exe