From Bespoke to Standard
Solid State Mass Memories
Aitor Viana Sánchez
Data Handling Systems
ESTEC, 27th Oct 2009
CCSDS Fall Meeting - 2009
Outline
• Solid State Mass Memories discussion
• What to standardize
• SOIS standard SSMM
• Summary
CCSDS Fall Meeting - 2009
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
CCSDS Fall Meeting - 2009
SSMM Traditional Design
OBC
Apps
File Access
Services
Bespoke File Access
and Packet Store
Services
Bespoke Network File
Access Protocol
Packet Access
Services
Network File Access Protocol
Physical Transport Services
Bespoke Transport
Services (data link layer
and protocol)
Network File Access Protocol
Packet Store
System
Bespoke Memory
Access Protocol
CCSDS Fall Meeting - 2009
File Store
Physical Transport Services
File System
Memory Access Protocol
Mass
Memory
Mass
Memory
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.
CCSDS Fall Meeting - 2009
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
CCSDS Fall Meeting - 2009
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??
CCSDS Fall Meeting - 2009
SSMM Standard SOIS Design (cont’d)
• The SSMM services standardization
OBC
Standardize File Access
and Packet Store
Services
Apps
FAS
FMS
FTS
Network File Access Protocol
Physical Transport Services
File Store
Physical Transport Services
Network File Access Protocol
Packet Store
System
CCSDS Fall Meeting - 2009
File System
Memory Access Protocol
Mass
Memory
Mass
Memory
SSMM Standard SOIS Design (cont’d)
• The SSMM services standardization
OBC
•
Apps
FAS
FMS
FTS
Network File Access Protocol
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
Physical Transport Services
File Store
Physical Transport Services
Network File Access Protocol
Packet Store
System
CCSDS Fall Meeting - 2009
File System
Memory Access Protocol
Mass
Memory
Mass
Memory
SSMM Standard SOIS Design (cont’d)
• 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
CCSDS Fall Meeting - 2009
SSMM Standard SOIS Design (cont’d)
• 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
CCSDS Fall Meeting - 2009
SSMM Standard SOIS Design (cont’d)
• 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)
CCSDS Fall Meeting - 2009
SSMM Standard SOIS Design (cont’d)
• The SSMM data link standardization
OBC
Apps
SOIS FPSS
Network File Access Protocol
MAS
ECSS
SpW
Standardize Transport
Services (data link layer
and protocol)
PS
ECSS
CAN
ECSS
1553
Physical Transport Services
Standardize Transport
Services (data link layer
and protocol)
SOIS Subnetwork Services
Network File Access Protocol
Packet Store
System
File System
Memory Access Protocol
CCSDS Fall Meeting - 2009
File Store
Physical Transport Services
ECSS extension protocols
Mass
Memory
Mass
Memory
SSMM Standard SOIS Design (cont’d)
• The SSMM data link standardization
OBC
•
Apps
SOIS FPSS
Network File Access Protocol
MAS
ECSS
SpW
PS
ECSS
CAN
ECSS
1553
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
Physical Transport Services
Standardize Transport
Services (data link layer
and protocol)
SOIS Subnetwork Services
Network File Access Protocol
Packet Store
System
File System
Memory Access Protocol
CCSDS Fall Meeting - 2009
File Store
Physical Transport Services
ECSS extension protocols
Mass
Memory
Mass
Memory
SSMM Standard SOIS Design (cont’d)
• 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.).
CCSDS Fall Meeting - 2009
SSMM Standard SOIS Design (cont’d)
• The SSMM Memory Access standardization
OBC
Apps
SOIS FPSS
Network File Access Protocol
SOIS Subnetwork Services
ECSS
SpW
ECSS
CAN
ECSS
1553
Physical Transport Services
File Store
Physical Transport Services
ECSS extension protocols
SOIS Subnetwork Services
Standardize Memory
Access Protocol
Network File Access Protocol
Packet Store
System
File System
i.e. Serial-ATA
CCSDS Fall Meeting - 2009
Mass
Memory
Mass
Memory
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