Exam SY0-501 topic 1 question 257 discussion

Correct answer: B. Implement deduplication on the storage array to reduce the amount of drive space needed, Data deduplication -- often called intelligent compression or single-instance storage -- is a process that eliminates redundant copies of data and reduces storage overhead. Data deduplication techniques ensure that only one unique instance of data is retained on storage media, such as disk, flash or tape. Storage arrays are simply powerful computers which have large amounts of storage connected to them. Storage arrays are configured in such a way that they can present storage to multiple servers, typically over a dedicated network.

Anyone has any clue about this question ? I have no idea what it is asking for.

Deduplication is the process of removing duplicate entries. As an example, imagine 10 users receive the same email and choose to save it. An email server using deduplication processing will keep only one copy of this email, but make it accessible to all 10 users. from Darril Gibson, Get certified get ahead

"replicate the backups to separate severs" mean data will replicate at server level, not at storage level, so the correct must be C

remember the ultimate destination which is data to reduce storage space

Is "B" talking about deduplicating the local storage array (SAN) or at the remote data center? If it's a local SAN, I can fully support the answer being 'B'. If it's a remote SAN, then the answer has to be 'C'.

They are not worried about saving space but cutting the back up time across the wire. Answer is C

The amount of drive space needed is ot the issue here. The question states that the main problem is the time it takes to transfer files from sites. So if we apply deduplication at a network level (using WAN accelerator technologies) this could go twice or even thrice faster.

B. Implement deduplication on the storage array - reduce data size, efficient compression

On further research I found that: There are two distinct methods of deduplication used for backup: Target-Based and Source-Based. Target-Based: Target-based deduplication employs a disk storage device as the data repository or target. The data is driven to the target using standard backup software. Once it reaches the device, the deduplication is processed as it enters the target (In-Line Processing), or it is received by the device in its raw data state and is processed after the entire backup job has arrived (Post-Process). There are two distinct methods of deduplication used for backup: Target-Based and Source-Based. Target-Based: Target-based deduplication employs a disk storage device as the data repository or target. The data is driven to the target using standard backup software. Once it reaches the device, the deduplication is processed as it enters the target (In-Line Processing), or it is received by the device in its raw data state and is processed after the entire backup job has arrived (Post-Process). In this context, I believe that C. is the best approach.

I'd go for A because it's not specified that they are backups are transferred using backup storage with block-level replication, so the only efficient (not so efficient TBH, but anyway better than nothing) way for both file-level and block-level replication it's on the network side. If you are deduplicating the source storage but transferring as file-level instead of block level, you won't gain anything fro deduplication on the transfer itself.

C. Not B: The question does not say that they are using storage arrays. The de-dup should occur prior to replication so that the smallest amount of data will be transmitted , taking the least amount of time. It says "The main bottleneck in the process is the time it takes to replicate the backups to separate severs at the offsite data center." So reduce the size of the data to be transmiited, then transmit it.

I use to work in storage and this one confused me, but after thinking about it a little more I understand why. My focus was typical backup technologies such as a rsync/robocopy or something similar. What they are not mentioning is block-level replication, not file level. Most major storage vendors allow you to do block-level replication, thus any deduplicated blocks would not get replicated like they would in a file-level replication.