Multiple SCSI controller for BE2012

[nhiatay]

Hi,

We have one HP DL380 G8 installed Windows 2012 which connect directly to one tape drive though SCSI controller and using Backup Exec 2012. My question is, can this backup software can support multiple SCSI controller? It mean can connect another tape drive on the separate SCSI controller to run multiple tape drive backup?

Thanks a lot.

Kevin

[Colin_Weaver]

Yes - although depending on scenario a library on the same controller might be a better option.

[Larry_Fine]

Windows Server 2012 isn't supported yet for a Backup Exec install.

[nhiatay]

Hi Colin,

Thanks for your information. Can you tell me what is different between multiple tape drive with separate SCSI host controller vs multiple tape drive with same SCSI controller?

Hi Larry,

The BE2012 is not fully compatible with server 2012, but it still can backup, sometimes will have software crash. We are still waiting the patch from symantec for this issue.

[Colin_Weaver]

If you use two stand alone tape drives then two jobs will run in parallel and having them on separate controllers will give a difference in performance (up to a point as the CPU, RAM and network cards will still have an impact) However if you fill a tape during one of the parallel jobs, the job will sit and wait asking you for media to be inserted and will not finish until you have done this.

If you have a library containing two drives and multiple slots to hold tapes then it will probably be on one controller (so lose the overall performance aspect) but can still run two parallel jobs and also has the additional benefit that if a tape fills during a job the library can automatically pick up another available tape from a different slot which helps avoid coming in the next day to find a job waiting for a new tape.

Also we will release the beta hotfix to support Windows 2012 in the next few weeks with public availabilty to follow. (Sorry that that I missed the Windows 2012 bit in my Yes answer earlier - yes was with relation to the hardware part of your question)

[Larry_Fine]

Can you tell me what is different between multiple tape drive with separate SCSI host controller vs multiple tape drive with same SCSI controller?

For most people, there would be little difference.  But the short answer, is YES, Backup Exec CAN support multiple HBAS, including a mix of parallel SCSI, SAS and fibre channel controllers.

The advantage of multiple SCSI controllers is possibly higher reliability since a SCSI HBA failure would only affect part of your devices.  Depending upon many other factors, it MIGHT offer higher performance/throughput.

Multiple SCSI controllers also require more management overhead as far as keeping the drivers and firmware updated, if they are not identical models.  Multiple SCSI controllers can also be a good thing and a bad thing when troubleshooting issues in that it lets you compare HBA1 to HBA2, but it can also make intermittent issues harder to identify.  And multiple HBAs cost more :)

[nhiatay]

Hi Colin,

If we use two separate SCSI controllers to run a parallel job, how about the general performance? Is it faster or slower when compare to standalone SCSI controller?

Above you mention the parallel job will pause if there are any tape need to fill on the tape drive. For example: we create a job1 backup to Tape Drive A and Tape Drive B at 10:00 PM daily, if there are no tape or tape need to replace on Tape Drive B while the job1 is running, the job1 will be pause and only resume until there are new tape inserted to Tape Drive B, right?

And as Larry type, The advantage of multiple SCSI controllers is possibly higher reliability since a SCSI HBA failure would only affect part of your devices, it mean if Tape Drive A SCSI controller is failed, the job also continue to run on Tape Drive B SCSI controller. Does that only the advantage for multiple SCSI controller?

Thanks.

[Colin_Weaver · Accepted solution]

In theory two controllers will be slightly faster - however the SCSI bus is not the only bottleneck for performance in a given environment as such what you will achive when you try it can only be found out whilst trying it. Bear in mind that tape drives themselves are typically a lot slower than the SCSI bus. So running two drives with two parallel jobs will get more data through than only 1 drive even if you only use 1 SCSI controller for both drives.

Also my pause (job waits asking for media) comment relates to what happens to any job to a drive that is not in a library (stand alone is the term we use for this) it is not specific to running jobs in parallel. With the parallel setup, it will only pause the job that actually needs the tape, the job on the other drive will continue.

A library gets around this pause by holding more tapes than the number of drives (so 2 drives but 20 tapes for instance)

With regards the reliability/resilience of multipe controllers then Larry's comment makes sense for 2 stand alone drives. This would be trickier to achieve with a libary as 2 libraries might be expensive and to share a single library over two paths (HBA cards) would probably need Fibre Channel SAN technology and Multipath software.