Brian

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"

Update:

http://teledynelecroy.com/support/knowledgebase.aspx?docid=415&typeid=2&capid=106&mid=530&smid=

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.

faq415-001_lg.jpg

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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