Typhoon: An Ultra-Available Archive and Backup System Utilizing Linear-Time Erasure Codes

Part of OceanStore...

Client Naming/LocationCache

Erasure Code: a form of data coding that allows lost portions of data to be recovered Idea is similar to ECC, except that the algorithm must be told which portions of the data are missing Reed Solomon Codes are a common type of Erasure Code, but they are computationally expensive and are usually implemented in hardware Erasure Codes

Tornado Codes: A Linear-Time Probabilistic Family of Erasure Codes Tornado Codes are linear time, but use probabilistic assumptions to “guarantee” that the decoding process will succeed A 1/2 rate Erasure Code will double the size of a file Any half of e. file can be used to recreate the original data T. Codes also require slightly more than half of the encoded file, thus trading a network bandwidth for speed –Inventors of T. Codes report that 5% is typical

File is divided into nodes of equal size (e.g. 512 bytes) Data Nodes are associated with Check Nodes using a series of Bipartite Graphs Contents of a Check Node is the XOR of its neighbors Bipartite Graphs are created to satisfy mathematical constraints that “guarantee” the recovery process will successfully recover the file Overview of Encoding Process Data Nodes Check Nodes Data File

Overview of Encoding Process Data Nodes Data File Check Nodes Once a file is encoded, the data nodes and check nodes are randomly distributed to a set of recipients

MMX: SIMD or Marketing? There are eight MMX registers Data in registers can be divided into four different sizes:

MMX: SIMD or Marketing? There are eight MMX registers Data in registers can be divided into four different sizes MMX has 57 instructions for 6 types of operations: —ADD —SUBTRACT —MULTIPLY —MULTIPLY THEN ADD —COMPARISON —LOGICAL AND NAND OR XOR

MMX: SIMD or Marketing? There are eight MMX registers Data in registers can be divided into four different sizes MMX has 57 instructions for 6 types of operations char array1[512]; char array2[512]; for(int i=0; i<512; ++i) array1[i]=array1[i] ^ array2[i]; MMX is 2.3 times faster than this (1.9 w/o pipeline sched.)

MMX: SIMD or Marketing? There are eight MMX registers Data in registers can be divided into four different sizes MMX has 57 instructions for 6 types of operations char array1[512]; char array2[512]; long * array1ptr=(long*)array1; long * array2ptr=(long*)array2; for(int i=0; i<512/sizeof(long); ++i) array1ptr[i]=array1ptr[i] ^ array2ptr[i]; MMX is 50% faster than this (22% w/o sched.)

MMX: SIMD or Marketing? There are eight MMX registers Data in registers can be divided into four different sizes MMX has 57 instructions for 6 types of operations char array1[512]; char array2[512]; long * array1ptr=(long*)array1; long * array2ptr=(long*)array2; for(int i=0; i<512; i+=32) xor32fast(array1ptr+i, array2ptr+i);

MMX: SIMD or Marketing? inline void xor32bytes(long * array1reg, long* array2reg, long* destreg) { _asm { mov eax, [array1reg] mov ecx, [array2reg] movq mm0, [eax] movq mm1, [ecx] movq mm2, [eax+8] movq mm3, [ecx+8] movq mm4, [eax+16] movq mm5, [ecx+16] movq mm6, [eax+24] movq mm7, [ecx+24] pxor mm0, mm1 ; 64-bit xor pxor mm2, mm3 ; 64-bit xor pxor mm4, mm5 ; 64-bit xor pxor mm6, mm7 ; 64-bit xor mov ecx, [destreg] movq [ecx], mm0 ; store result movq [ecx+8], mm2 ; store result movq [ecx+16], mm4 ; store result movq [ecx+24], mm6 ; store result }

MMX: SIMD or Marketing? inline void xor32fast(long * array1reg, long* array2reg, long* destreg) { _asm { mov eax, [array1reg] mov ebx, [array2reg] mov ecx, [destreg] movq mm0, [eax] ; load 1a U movq mm1, [ebx] ; load 1b U movq mm2, [eax+8] ; load 2a U V pxor mm0, mm1 ; xor 1 movq mm3, [ebx+8] ; load 2b U movq [ecx], mm0 ; store 1 U V pxor mm2, mm3 ; xor 2 movq mm4, [eax+16] ; load 3a U movq mm5, [ebx+16] ; load 3b U movq mm6, [eax+24] ; load 4a U V pxor mm4, mm5 ; xor 3 movq mm7, [ebx+24] ; load 4b U movq [ecx+8], mm2 ; store 2 U V pxor mm6, mm7 ; xor 4 movq [ecx+16], mm4 ; store 3 U movq [ecx+24], mm6 ; store 4 U }

Overview of Encoding Process Server sends storage announcement to a particular set of severs –Set can be determined/specified using multicast groups, a server list, or some form of DNS address lookup UDP

Overview of Encoding Process Server sends storage announcement to a particular set of severs –Set can be determined/specified using multicast groups, a server list, or some form of DNS address lookup Multicast

Overview of Encoding Process Server encodes file During encoding process, the data nodes and check nodes are [randomly] distributed to other servers

A set of nodes are received, ideally with random distribution Check nodes can be used to recover missing data nodes Only check nodes that are missing one neighbor can recreate a data node The structure of the graph ensures [w.h.p.] that the encoding process will succeed –Graph is designed so that there is always at least one check node that is missing only one child –Data nodes can be used to recover check nodes, but is not important Overview of Decoding Process Check Nodes Data File Node Received Node Not Received

A set of nodes are received, ideally with random distribution Check nodes can be used to recover missing data nodes Only check nodes that are missing one neighbor can recreate a data node The structure of the graph ensures [w.h.p.] that the encoding process will succeed –Graph is designed so that there is always at least one check node that is missing only one child –Data nodes can be used to recover check nodes, but is not important Overview of Decoding Process Check Nodes Data File Node Received Node Not Received

A set of nodes are received, ideally with random distribution Check nodes can be used to recover missing data nodes Only check nodes that are missing one neighbor can recreate a data node The structure of the graph ensures [w.h.p.] that the encoding process will succeed –Graph is designed so that there is always at least one check node that is missing only one child –Data nodes can be used to recover check nodes, but is not important Overview of Decoding Process Check Nodes Data File Node Received Node Not Received

A set of nodes are received, ideally with random distribution Check nodes can be used to recover missing data nodes Only check nodes that are missing one neighbor can recreate a data node The structure of the graph ensures [w.h.p.] that the encoding process will succeed –Graph is designed so that there is always at least one check node that is missing only one child –Data nodes can be used to recover check nodes, but is not important Overview of Decoding Process Check Nodes Data File Node Received Node Not Received

A set of nodes are received, ideally with random distribution Check nodes can be used to recover missing data nodes Only check nodes that are missing one neighbor can recreate a data node The structure of the graph ensures [w.h.p.] that the encoding process will succeed –Graph is designed so that there is always at least one check node that is missing only one child –Data nodes can be used to recover check nodes, but is not important Overview of Decoding Process Check Nodes Data File Node Received Node Not Received

A set of nodes are received, ideally with random distribution Check nodes can be used to recover missing data nodes Only check nodes that are missing one neighbor can recreate a data node The structure of the graph ensures [w.h.p.] that the encoding process will succeed –Graph is designed so that there is always at least one check node that is missing only one child –Data nodes can be used to recover check nodes, but is not important Overview of Decoding Process Check Nodes Data File Node Received Node Not Received

A set of nodes are received, ideally with random distribution Check nodes can be used to recover missing data nodes Only check nodes that are missing one neighbor can recreate a data node The structure of the graph ensures [w.h.p.] that the encoding process will succeed –Graph is designed so that there is always at least one check node that is missing only one child –Data nodes can be used to recover check nodes, but is not important Overview of Decoding Process Check Nodes Data File Node Received Node Not Received

A set of nodes are received, ideally with random distribution Check nodes can be used to recover missing data nodes Only check nodes that are missing one neighbor can recreate a data node The structure of the graph ensures [w.h.p.] that the encoding process will succeed –Graph is designed so that there is always at least one check node that is missing only one child –Data nodes can be used to recover check nodes, but is not important Overview of Decoding Process Check Nodes Data File Node Received Node Not Received

A set of nodes are received, ideally with random distribution Check nodes can be used to recover missing data nodes Only check nodes that are missing one neighbor can recreate a data node The structure of the graph ensures [w.h.p.] that the encoding process will succeed –Graph is designed so that there is always at least one check node that is missing only one child –Data nodes can be used to recover check nodes, but is not important Overview of Decoding Process Check Nodes Data File Node Received Node Not Received

A set of nodes are received, ideally with random distribution Check nodes can be used to recover missing data nodes Only check nodes that are missing one neighbor can recreate a data node The structure of the graph ensures [w.h.p.] that the encoding process will succeed –Graph is designed so that there is always at least one check node that is missing only one child –Data nodes can be used to recover check nodes, but is not important Overview of Decoding Process Check Nodes Data File Node Received Node Not Received

A set of nodes are received, ideally with random distribution Check nodes can be used to recover missing data nodes Only check nodes that are missing one neighbor can recreate a data node The structure of the graph ensures [w.h.p.] that the encoding process will succeed –Graph is designed so that there is always at least one check node that is missing only one child –Data nodes can be used to recover check nodes, but is not important Overview of Decoding Process Check Nodes Data File Node Received Node Not Received

A set of nodes are received, ideally with random distribution Check nodes can be used to recover missing data nodes Only check nodes that are missing one neighbor can recreate a data node The structure of the graph ensures [w.h.p.] that the encoding process will succeed –Graph is designed so that there is always at least one check node that is missing only one child –Data nodes can be used to recover check nodes, but is not important Overview of Decoding Process Check Nodes Data File Node Received Node Not Received

A set of nodes are received, ideally with random distribution Check nodes can be used to recover missing data nodes Only check nodes that are missing one neighbor can recreate a data node The structure of the graph ensures [w.h.p.] that the encoding process will succeed –Graph is designed so that there is always at least one check node that is missing only one child –Data nodes can be used to recover check nodes, but is not important Overview of Decoding Process Check Nodes Data File Node Received Node Not Received

A set of nodes are received, ideally with random distribution Check nodes can be used to recover missing data nodes Only check nodes that are missing one neighbor can recreate a data node The structure of the graph ensures [w.h.p.] that the encoding process will succeed –Graph is designed so that there is always at least one check node that is missing only one child –Data nodes can be used to recover check nodes, but is not important Overview of Decoding Process Check Nodes Data File Node Received Node Not Received

Overview of Decoding Process Server sends file request announcement to a particular set of servers Retrieves data from multiple servers simultaneously Recovery process can be performed in parallel with receive (network-based RAID-1) Depending on data loss pattern, a particular subset of the servers can be selected Fastest servers (closest servers, or least utilized servers) Operational Servers (i.e., some portion of the set is not functioning) All servers might be needed in some cases, such as network congestion / packet loss

Client Naming/LocationCache Architecture

Architecture What did we implement? Client, Cache, Naming and Location Mechanism, Replication mechanism, filestore. What did we test? Communication Explicit communication  Unicast request Implicit communication  Multicast request Network Distributed servers throughout Berkeley domain. Simulated network delay by randomizing response time. Caching None for worst case Simulation Strained the Typhoon system by creating requests at the same rate as a 24 hour NFS traces over a 3 hour period.

Typhoon: An Ultra-Available Archive and Backup System Utilizing Linear-Time Erasure Codes Benefits of Typhoon Data is ultra-available: up to half of the servers can fail before availability is affected Fast file retrieval: data can be retrieved simultaneously from multiple servers – System can choose to use the fastest machines in a set of servers – Load balancing can be achieved because slow or heavily utilized servers are not used –Information can be disbursed geographically Increases the accessibility of data in the event of a major disaster, such as an earthquake Can benefit people who travel to remote locations, since data may be closer to them –Multicast can be used to reduce latency Low-overhead algorithms: algorithms for encoding and decoding are linear-time Disk overhead of system can be adjusted (typically doubles the size of a file)

Conclusion Tornado Codes are significantly faster than Cauchy-Reed Solomon A Typhoon based system can match the the request of a loaded NFS Typhoon is a viable solution for increasing the reliability and accessibility of data

Architecture What did we implement? Client, Cache, Naming and Location Mechanism, Replication Mechanism, filestore. What did we test? Communication Explicit communication  TCP request, TCP Response. Implicit communication  Multicast request, TCP Response. Network Distributed servers throughout Berkeley domain. Simulated network delay by randomizing response time. Caching None for worst case Simulation Strained the Typhoon system by creating requests at the same rate as a 24 hour NFS traces over a 3 hour period.