I hope it will be as you said..
This is the last EMC response: https://support.emc.com/kb/470374Issue
Read performance is poor on a DD2500 system.
Cause When using systems with no external shelves and only disks in the head unit, sustained read performance of 45-50MB/s is common. The reason for this low performance is that I/O bandwidth on such systems is extremely limited as they lack additional spindles/controllers across which multiple I/O operations can be performed in parallel. In addition, internal head-unit disks are shared with the DD OS operating system and as such reading of de-duplicated data from these disks also has to complete with normal I/O performed by the operating system (for example writing of log files and so on).
Note that in DD OS performance guides we publish figures for expected sustained read throughput on DD2500 systems (for example single stream reads via CIFS on DD OS 5.5 is shown at 129MB/s). However, these figures were obtained via testing on clean systems with a minimum of three external enclosures. As a result systems configured with less than 3 external enclosures will not be able to obtain similar throughput and as enclosure count drops corresponding read performance degrades rapidly.
Resolution RECOMMENDATIONS: To allow systems to achieve read performance loosely in line with figures documented in DD OS performance guides, DD2500 systems should be configured with a minimum of three external enclosures. Where this is not possible customers should be made aware of the likely impact to read performance to ensure that the system will still be able to meet baseline performance expectations.
WORKAROUND: For systems which have already been implemented with low shelf count and are experiencing poor read throughput, the first step is to perform normal investigations to rule out common causes of poor performance (such as issues in the environment or configuration of the DDR, file system fragmentation, system load, or poor data locality).
Once it has been determined that poor read performance is due to the systems becoming I/O bound during read, the only way in which performance can be improved is to:
Add additional external enclosures (to give increased I/O bandwidth)
Expire existing backup data and run clean (to remove existing data from the system)
Re-write backup data to the DDR
Note that if enclosures are added but data is not rewritten, the systems' read performance may not significantly improve. This is because the DDR will not automatically rebalance data across enclosures and as a result the majority of data will still be being read from existing enclosures so issues with a lack of I/O bandwidth to these existing enclosures will still be apparent.
The documented CIFS single stream read performance for DD2500 using a 10Gbps network with the recommended 3 shelves is 129MB/s. However, the multiplier for having 0 external shelves is 0.34. From this we get:
129 * 0.34 = 43.86MB/s which is in line with the number reported in the "CAUSE" section above.
In our case, our read performance is about 1 MB/s (when we are lucky), and only with DDBoost feature, because if we use CIFS share the performance grow up to the fantastic value of 30 MB/s !
Our system is DD2200, I think it doesn't support shelf addiction..