ccsds fall meeting - 2009 from bespoke to standard solid state mass memories aitor viana sánchez...

CCSDS Fall Meeting - 2009

From Bespoke to Standard Solid State Mass Memories

Aitor Viana Sánchez

Data Handling Systems

ESTEC, 27th Oct 2009


Outline

• Solid State Mass Memories discussion

• What to standardize

• SOIS standard SSMM

• Summary


Solid State Mass Memories discussion

• It should be possible to develop a SSMM as a standard building block capable of being used for multiple missions, but:

– For maximum architectural flexibility, a relatively low level interface should be defined to the SMMM

– Unfortunately this is often implemented with a proprietary data link layer, network file and packet access protocols, and services

• This means that the required software to access the SSMM has to be defined, developed and validated for each mission


SSMM Traditional Design

Physical Transport Services

Apps

File Access Services

Packet Access Services

OBC

File System


Mass Memory

Bespoke File Access and Packet Store

Services

Bespoke Transport Services (data link layer

and protocol)

Bespoke Network File Access Protocol

Network File Access Protocol

Network File Access Protocol Mass Memory

Bespoke Memory Access Protocol Memory Access Protocol

File Store

Packet StoreSystem


SSMM Traditional Design

• The SSMM services change from design to design– The SSMM services provided from the SSMM to operate with the files, i.e.

open, read, write, lock, etc. may vary a lot from unit to unit.

• The SSMM services implementation change from unit to unit– Even standardizing the services it is possible to implement them with many

different APIs. It might be probably helpful to establish a common API

• The SSMM data link change from unit to unit– There is the need to standardize the way the information is transferred

between the entities (SSMM and OBC, payloads, etc)

• The SSMM memory access protocol change from unit to unit– Wherever the File System is located, local to the OBC or remote in the

SSMM, there is an access protocol from the FS to the memory devices. The standardization of this protocol is also standardize (i.e. Serial-ATA) would allow to exchange also the memory technology without any problem.

• To provide a SSMM building block that can be used reused for multiple missions all these interfaces need to be standardized.


SSMM Standard SOIS Design

• Standardization of the SSMM services

– The standardization of the SSMM services is provided using the File Access Service (FAS), File Management Service (FMS), File Transfer Service (FTS) and Packet Store Services (PSS)

– The Network File System Protocol specifies the way the file system or packet store system are accessed. The suite of command/response sequences used to perform the operations specified in the SOIS services. SOIS does not define any NFSP nor recommend any but shall be implemented within FAS, FMS and FTS and might differ from unit to unit


SSMM Standard SOIS Design

• Standardization of the SSMM services

– The standardization of the SSMM services is provided using the File Access Service (FAS), File Management Service (FMS), File Transfer Service (FTS) and Packet Store Services (PSS)

– The Network File System Protocol specifies the way the file system or packet store system are accessed. The suite of command/response sequences used to perform the operations specified in the SOIS services. SOIS does not define any NFSP nor recommend any but shall be implemented within FAS, FMS and FTS and might differ from unit to unit

• Should the Network File System Protocol be specified or recommended within SOIS??


SSMM Standard SOIS Design (cont’d)

• The SSMM services standardization

Apps

FAS

OBC


FMS FTS

Standardize File Access and Packet Store

Services

File System


Mass Memory


Memory Access Protocol

File Store

Packet StoreSystem




• The SSMM services standardization

Apps

FAS

OBC


FMS FTS

• The SOIS FSPS standardize the user interface towards the SSMM but still lots of changes would be necessary in the Network File System Protocol to adapt to all possible different data link implementations for different SSMM units

File System


Mass Memory



File Store

Packet StoreSystem




• Network File System Protocol– Under the RASTA SSMM activity a custom NFSP has been

developed and some useful findings came out

– The developed protocol is a command-response protocol as File Operations requires confirmation (ACK) for all services

– 1024 bytes SDU size was selected but up to 8KB may be used under Spacewire

– The physical link used may be both Eth and Spacewire

– Ethernet case (Spacewire may be extrapolated)

• The protocol overhead is 90%. This protocol overhead is not only due to the protocol headers but the way the operating system handles the internal resources (context switch, interrupt service routines, etc.)

– To ensure the results test with netperf tool have been performed

• “netperf” does not do anything with the data



• Network File System Protocol (cont’d)– Test has been performed for:

• UDP_RR: send one packet and waits for ACK for sending next one

• UDP_STREAM: best effort sending (no ACKs)

• TCP_STREAM: like UDP_RR but using TCP window

• TCP_RR: like TCP_STREAM without sending window (like UDP_RR but using TCP)

Link speed

1000Mbps

100 Mbps

10 Mbps

UDP_RR 18.64 Mbps 24.24 Mbps 2.08 Mbps

UDP_STREAM 961 Mbps 95.80 Mbps 9.75 Mbps

TCP_RR 18.3 Mbps 24 Mbps 2.08 Mbps

TCP_STREAM 940 Mbps 93.68 Mbps 9.4 Mbps



• Standardization of the Data Link Layer– SOIS FPSS maps down to the SOIS Packet Service (PS) and SOIS

Memory Access Services (MAS), but the introduction of the SOIS Subnetwork services does not standardize the Data Link layer protocol. For that we need to agree the way the data is transferred through the physical bus.

Thus, all the SOIS Subnetwork services will map down with the ECSS extension protocols

• ECSS CAN (ECSS-E-ST-50-15)

• ECSS MIL-STD-1553 (ECSS-E-ST-50-13C)

• ECSS Spacewire (TBD)



• The SSMM data link standardization

Standardize Transport Services (data link layer

and protocol)


and protocol)


Apps

OBC


SOIS FPSS

ECSSSpW

ECSSCAN

ECSS1553

PSMAS

File System

Mass MemoryNetwork File Access Protocol

Mass Memory


File Store

Packet StoreSystem

SOIS Subnetwork ServicesECSS extension protocols




• The SSMM data link standardization


and protocol)

File System


Mass Memory


File Store

Packet StoreSystem


OBC


SOIS FPSS

ECSSSpW

ECSSCAN

ECSS1553

PSMAS

• The SOIS Subnetwork MAS and PS services mapped down to the ECSS bus extension protocols fully standardize both the data link layer and data link protocol.SSMM units complying with this approach become reusable building blocks

Apps





• Standardization of the Memory Access– Out of the SOIS scope

– The file system (or packet store) interfaces to the memory devices by means of a Memory Access Protocol (MAP). This MAP has not being standardize for space usage but examples might be take from commercial world, i.e. Serial-ATA

– Standardizing this protocol will de-couple the SSMM design from the memory device technology (RAM, Flash, Solid-state drives, etc.).



• The SSMM Memory Access standardization

Standardize Memory Access Protocol

File System


Mass Memory

i.e. Serial-ATA

File Store

Packet StoreSystem


OBC


SOIS FPSS

ECSSSpW

ECSSCAN

ECSS1553

SOIS Subnetwork Services

Apps




Summary

• SSMM should become standard building blocks to be reused for multiple missions

• SOIS assists in the standardization process by providing:– SOIS File and Packet Store Services standardize the SSMM services

• Standard Network File System Protocol (TBC) ?

– SOIS sub-network Packet and Memory Access Services standardize the Data link

• ECSS bus extension protocols also standardize the data link transfer protocol

• Outside the scope of CCSDS SOIS, the memory access protocol used by the to the file system (or packet store system) to access the memory devices could also be standardized, making the SSMM independent from the memory technology being used

ccsds fall meeting - 2009 from bespoke to standard solid state mass memories aitor viana sánchez...

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