Netbackup 7.5 Accelerator and Client-side Deduplication

Hi all,

I've gone through the parts about Accelerator in the 7.5 Admin guide.
I've read though the 7.5 Deduplication guide.
I've read the "Netbackup Accelerator Feature Briefing" document that is only accessible in the seclusive Symantec IQ for Partners portal.

I understand that:
"NetBackup Accelerator should be regarded as a complimentary technology of client deduplication, not replacement for it".

From what I gathered, there doesn't seem to be any disadvantage to using Accelerator.
It almost seems like there is no reason not to enable it, when client-side deduplication is already in use.

My 1st question:
Are there situations in which Accelerator should NOT be enabled when doing client-side deduplication?

I know that Accelerator only supports two policy types, "MS-Windows" and "Standard";
if you disable Accelerator, you could still use client-side deduplication with other policy types such as "Flashbackup".

But apart from that, is there a reason not to use Accelerator when using client-side deduplication?

2nd question:
To force client-side deduplication, the following would have to be set for a client:
Host Properties > Master Servers > Client Attribute > Always use client-side deduplication

What about if I enable Accelerator in the policy attributes WITHOUT setting the above?
Seeing that Accelerator is based on (or works with) Client-side deduplication, what would happen if I don't specify "Always use client-side deduplication"? would Accelerator still work as it is supposed to? Worst still, what if I mistakenly set "Always use the media server for deduplication" for the client?

If Accelerator would still work, then that means by simplying enabling Accelerator in a policy, the "Always use client-side deduplication" attribute is automatically forced on all the clients in the policy.
If it wouldn't work, then the guides should have mentioned that you have to set "Always use client-side deduplication" for clients inside an Accelerator enabled policy.

Thanks all,

RLeon

7.5

Agents

AbdulRasheed
13 years ago

Hi RLeon et al,

Sorry to be late in this party. You guys have a great discussion going here. In the interest of saving time for someone newly following this thread, I tried to consolidate the questions and provide answers in this blog . Some of these might be obvious to most of you and some of them might have already been answered, I am listing them just to give a full perspective.

As Jed already mentioned, if you have a specific issue with growing track log, please do work with technical support.

19 Replies

revarooo
Level 6
13 years ago
From memory, no you don't have to set client side deduplication, you can just do normal backup with Accelerator enabled. You MUST be sending the data to a storage unit that supports Accelerator (Dedup, Puredisk, Cloud)
RLeon
Level 6
13 years ago
Thanks for your input revaroo.

I understand the storage unit prerequisites for using Accelerator.

What you are saying validates my hypothesis:
"... by simplying enabling Accelerator in a policy, the "Always use client-side deduplication" attribute is automatically forced on all the clients in the policy."

That means even if the client normally uses media server deduplication, it will be forced to start using client-side deduplication when you enable Accelerator in the policy.

So then, what if I mistakenly set "Always use the media server for deduplication" for the client? Would Accelerator still work?

Also, can you point me to some answers for my 1st question?

Thanks,

RLeon
Peter_Jakobs
Level 5
13 years ago
If you are low on disk space on the client side you can have a problem with the accelerator. I've seen clients with a tracking file of several GB, (and I've seen clients with a disk full thanks to the tracking file)

Peter
marcelg
Level 3
13 years ago
I wonder what uses less space - the tracking file or the NTFS Change Journal
RLeon
Level 6
13 years ago
I must say I wasn't expecting to see a (potential) fault for being a reason NOT to use Accelerator. But this is useful information, so thanks Peter Jakobs.
I hope they talk more about this tracking file growth problem in the guides.

I was actually expecting to see something along the lines of:

"...under such and such conditions, enabling Accelerator would result in lower bandwidth/cpu/storage resource utilization and the backup becomes less efficient.
But in all other cases, always use Accelerator when using Client-side deduplication..."

...or somesuch.

Thanks,

RLeon
marcelg
Level 3
13 years ago
Accelerator and Client-side deduplication are two independent but potentially complementary product features as far as I know.

The customer should always be allowed to choose whether to enable client-side deduplication because of the potentially negative impact on client performance during backups.
RLeon
Level 6
13 years ago
Just found another quirk about Accelerator that isn't documented (Ok, I agree this one is a little obvious anyway...):

If you enable Accelerator in a policy's attribute tab, the "compression" and "encryption" check boxes will be disabled.

But then when you think about it, it doesn't really matter, because if you use Accelerator, you are using deduplication anyway.

And as we all know, when using deduplication you cannot use the policy attributes's "compression" and "encryption" options. You have to use the deduplication engine's very own comperssion and encryption features.

RLeon
RLeon
Level 6
13 years ago
Anyone with any design considerations and best practices on when and when not to enable Accelerator for client-side deduplication backups?
RLeon
Level 6
13 years ago
Anyone from Symantec wants to add anything to this?

It is going to be difficult when more and more customers ask the same question...
vholmes
Level 3
13 years ago
I guess the only thing that really bothers me...

If you enable Accelerator, because it also uses Synthetics on the back side, you are unable to create synthetic backups. For me I do fulls on the weekend, diffs durring the week, but I have to run all the diffs to get a restore to Thursday. If I just did client side dedup and synthetics the restores would be a little quicker.

Lastly I get random 83s, 14s on some really big file servers. Maybe I am missing something but that is my experience.