SanDisk Optimus Eco 400GB SAS SSD Review Discussion

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What do they mean exactly by "Sustained Read/Write: 500/500 MB/s (Dual) or 1GB/s (Wide Port)"?

I know that SAS is dual-ported: there are 2 x rows of 7-pin data connectors on a single SAS block connector.

But, what is actually happening, functionally speaking, with "1GB/s (Wide Port)"?

Let's consider a simple READ task, i.e. reading a single file:

are the 2 data paths used in "sync" to transmit that binary data

twice as fast? somewhat like RAID-0 breaks up a file into

small chunks via "striping"?

Or, is something else happening?

SAS has been around a long time, and I thought the design

was "dual-ported" to permit redundant access to a SAS drive

by two different host systems: thus, if one system halted,

the second system could still access the entire SAS drive

via a second data connector.

Since we don't use SAS drives here, I suspect that there

is a second mode I'm not familiar with, as implied by this sentence:

"an interface that provides both dual and wide SAS connectivity"


Expanders have a profound effect on test and analysis because they have a unique ability to use different physical pathways across a wide link to complete a single SCSI operation. This means the SAS Initiator can open a connection to a SAS target device yet complete the transfer over a different physical connection. These transfers over wide links may change their pathways dynamically within the expander device.


This increases the complexity of SAS test and debug because it requires users to monitor multiple links concurrently to record all dwords associated with a single SCSI transaction. Engineers can't predict or control which physical pathway is used which means they must have the ability to monitor all relevant paths. Only by monitoring all 4 links in a wide connection can the user be assured they will record all frames associated with the transfer.

Edited by MRFS

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