D2D Deduplication Virtual Tape

Analyst Commentary on VTL

I am often perusing industry related sites to find what people are saying about disaster recovery and data protection. Most of these sites rely on independent contributors to provide the content. Given the myriad of viewpoints and experience levels, it is not uncommon to see a wide range of commentaries, some consistent with industry trends, and others not. I keep this in mind when reading these articles and generally ignore inconsistencies; however once in a while an article is so egregiously wrong that I feel a response is necessary.

In this case, I am referring to an article appearing in eWeek where the author makes gross generalizations about VTL that are misleading at best. Let’s walk through his key points:

VTLs are complex

I completely disagree. The reason most people purchase VTLs is that they simplify data protection and can be implemented with almost no change in tape policies or procedures. This means that companies do not have relearn new procedures after implementing a VTL and thus the implementation is relatively simple and not complex like he suggests.

He also mentions that most VTLs use separate VTL software and storage. This is true for solutions from some of the big storage vendors, but is not the case with the SEPATON S2100-ES2. We manage the entire appliance including storage provisioning and performance management.

Finally, he complains about the complexity of configuring Fibre Channel (FC). While it is true that FC can be more complex than Ethernet it really depends on how you configure the system. One option is to direct connect the VTL which requires none of the FC complexities he harps on. He also glosses over the fact that FC is much faster than the alternatives which is an important benefit. (My guess is that he is comparing the VTL to Ethernet, but he never clearly states this.)

VTLs increase total backup completion times

VTLs are typically much faster than tape and so from a pure backup window standpoint, a customer will typically see a substantial reduction in backup window when implementing a VTL. (SEPATON’s S2100-ES2 provides 300 MB/sec single stream performance!)

He then goes on to say that the real problem is creating offsite tapes and he talks about how it is a 3 step process. This is true, but the reality is that the same three step process is used for physical tape as well. Most customers maintain a copy of the data onsite in the physical tape library and copy at the DR site. Thus they need two copies even with physical tape, and the creation process is a three-step process for tape just like disk. ([during backup] backup server –> tape library, [during tape copy/vaulting] tape library –> backup server, backup server –> tape library

The question that he misses is “Would you rather use a tape-to-tape copy mechanism to create offsite tapes or a disk-to-tape copy process?” The answer is obvious. You will always want a disk-to-tape copy because of the improved performance and reliability.

VTLs extend time to DR

I am not sure what the point is here. Time to DR is the time it takes to complete the backup, copy the data to tape and get the data offsite. As mentioned above, VTL will dramatically outperform tape in the process of both backing up and copying data thus improving DR time.

He also talks about VTL replication. This is an entirely separate discussion and users need to review this in the context to their offsite requirements. One side note, is that SEPATON’s Site2 technology integrates with the backup application so data is replicated in a manner that is dictated by the backup application’s policy engine.

Most VTL restores are not from disk

This is just not true. If you ask most users, they will tell you that something like 80% of their restore requests is for data that is less than 2 weeks old. The goal would then be to implement a VTL that allows for 2 weeks retention. If you do this then more than ¾ of your restores will come from disk. 90%+ of our customers are retaining at least two weeks of data on the VTL. Perhaps he is assuming that the VTL is tiny that you only retain a few days on disk? If so, then most restores would be from tape, but that is a very inaccurate assumption and does not match reality.

VTLs do not reduce tape media expenditures

The impact of VTL on tape media expenditures depends on how customers use tape. As mentioned previously, the vast majority of customers use VTL to replace tape assets that were kept onsite prior to VTL. In this scenario, they will recognize immediate savings because they can replace all of those onsite tapes with a VTL and will only need tape for offsite purposes.

VTLs offer inefficient deduplication

This is a ridiculous gross generalization. His lack of knowledge is further reflected in the following statements:

To compensate for their lack of value, VTLs have attempted to add data deduplication as a product feature
Again, he is showing his bias here and clearly he thinks that there is no value in VTL. Industry statistics and real world customer experiences indicates otherwise.

The challenge is, because most of these systems have deduplication as a post-process
The question of post-process vs inline is an entirely separate discussion than VTL or no VTL. There are VTL vendors who offer inline deduplication and those who offer post-process. Suggesting that somehow VTL requires post-process is just idiotic.

In short, this article reflects an extremely biased via of the world. The author seems pre-disposed to hate VTL and is trying to do everything he can to discredit the technology. The article shows a clear lack of understanding of VTL and makes me wonder about the original author’s real agenda. I think that the most realistic assumption is that he is being unduly influenced by a vendor (because he is being paid or is otherwise involved) and thus providing a biased opinion.

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