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(Speaker Notes Version) Architecting An Enterprise Storage Platform Using Object Stores


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Presented at SNIA SDC 2013. This deck adds speaker notes.

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(Speaker Notes Version) Architecting An Enterprise Storage Platform Using Object Stores

  1. 1. Architecting an Enterprise Storage Platform Using Object Stores © mekuria getinet / Niraj Tolia Chief Architect, Maginatics @nirajtolia
  2. 2. These gray slides are equivalent to speaker notes Normally invisible, they are provided for non- presentation settings Hope they help
  3. 3. A Whirlwind Tour
  4. 4. This presentation provides an end-to-end overview of MagFS and therefore might not be deep enough in certain areas Contact @nirajtolia for Comments, Questions, Flames
  5. 5. Awesome Questions == AwesomeT-shirts
  6. 6. Hacker T-shirts were handed out for “awesome” questions during the SNIA SDC talk. If you asked one but didn’t get one, get in touch with us and we will ship one. If you missed the talk and still want a T-shirt, come to a future talk or try MagFS out.
  7. 7. 80%YoY Growth in Unstructured Data 41% Growth in IaaS Systems through 2016 Sources: Gartner, IT Marketing Clock for Storage, Sep 2011 Gartner, Forecast Overview: Public Cloud Services, Worldwide, 2011-2016, Feb 2013
  8. 8. Data growth is impressive! Requires centralization for protection, analysis and cost management. Infrastructure-as-a-Service systems are rapidly growing. Apart from leveraging new storage paradigms (object storage) to deal with this data growth, workloads are migrating and need to use cloud storage. Storage systems also need to support elastic workloads (capacity and scale).
  9. 9. MagFS –The File System for the Cloud Consistent, Elastic, Secure, Mobile-Enabled Layered on Object Stores “Software-Defined”
  10. 10. To respond to the earlier trends, we built a system that, at its core, is a distributed file system It differs from legacy systems in a number of ways but primarily with an end-to-end (E2E) security perspective, the ability to both be elastic and support elastic workloads, by elevating mobility to a first-class citizen, and by exploiting object stores Further, while “software-defined” is a oft-abused buzzword, MagFS does fit the definition: software-only, packaged as VMs, and clean separation of data and control planes
  11. 11. No (Initial) Legacy Support (NFS/CIFS) Native Clients: Push Intelligence to Edges Strong Consistency w/ Full-Spectrum Caching
  12. 12. Three Early Decisions: 1. No legacy (NFS, CIFS) support on purpose: File systems must evolve (e.g., dedup, caching, scaling). MagFS transparently replaces legacy distributed file systems though. 2. Client agents allows MagFS to push smarts to edges. No significant IT pushback anymore. Common codebase reduces development costs. 3. Enable data & metadata caching with strong consistency
  13. 13. File System Design Goals Low Cost, High Scale Intelligent Clients Span Devices and Networks Support Rapid Iteration
  14. 14. Design Goals: 1. Deliver scale at a cost-effective point 2. Make clients intelligent: modern computing platforms have enough horsepower 3. Span server-grade hardware to mobile clients and from fast to bandwidth-challenged networks 4. To rapidly iterate on our product and add new features with disruption to users
  15. 15. In-Cloud File System NAS Replacement and Consolidation Enterprise File Sharing Use Cases
  16. 16. MagFS, a general purpose system, is used for many different use cases.The majority are Tier 2/3 workloads (e.g., home directory, media, nearline storage, etc.). In-Cloud File System:Allow unmodified applications to Just Work™ in the cloud. Provide a distributed file system where no filer can be racked in. NAS: Both serve as a more cost-effective filer as well as allow for globally distributed workforces to leverage our WAN optimization. Enterprise File Sharing: Related to NAS, secure file sharing that meets compliance and regulatory concerns as MagFS is a product and not a service.
  17. 17. Object Storage (public, on-premises,or hybrid) Data Metadata Metadata Servers Clients 10,000 FootView
  18. 18. The previous slide presents a very high-level overview of MagFS Note the split data and metadata planes: MagFS does not try to resolve scalability issues already tackled by the object storage system and therefore will not intercept data on the fast path The metadata servers provide a single pane-of-glass for admins, integrate with native AD or LDAP setups, and also store encryption keys
  19. 19. Koukouvaya / Heavy (Data) Lifting via Clients Encryption Inline Deduplication Compression Persistent Data Caching Bulk DataTransfers
  20. 20. Push a lot of smarts to increasingly-powerful clients Clients do heavy data lifting: Chunking for deduplication, encryption, optional compression, on-disk caching, etc. Available resources generally proportional to workloads for different device types Server doesn’t see data on read OR write path!
  21. 21. Cloud Object Storage Scale Out, Low Cost Handles Placement + Replication Tolerates Failures High Aggregate Performance
  22. 22. Object Storage has a number of very useful properties: Cost, Commodity, Scale Out (aggregate performance, fault tolerance, etc.) We directly expose clients to the object store Similar to clients, we also push functionality to the object storage system: data placement and replication, fault-tolerance, repairs, etc. as we do not want to reinvent the wheel
  23. 23. Virtualized Metadata Servers Enforce Strong Consistency Enforce Authentication and Integrity Runtime Performance Optimization Share-level Deduplication Data Scrubbing & Garbage Collection
  24. 24. TheVM-based metadata servers are where consistency and user authentication are enforced They also allow clients to dynamically cache read and write data, lock objects and byte ranges, etc. Works with clients to prevent duplicated data transfers or redundant data copies Data is scrubbed and unused data deleted in the background
  25. 25. Architecture
  26. 26. We will now branch off into details about the client and server architecture and how they interact with object storage
  27. 27. Client Architecture
  28. 28. MagFS supports different Linux,Windows, OS X, Android, and iOS versions Majority of code is shared across platforms with platform-specific glue layers The next few slides talk about desktop/server platforms but the same structure applies to all.
  29. 29. Client Architecture Application Redirector (e.g., FUSE) File System OS Glue Data Manager MetadataTransport Layer Local Remote Userspace Kernel Deduplication Encryption Compression Locking Leases
  30. 30. Traditional platforms have a thin in-kernel redirector (FUSE on Linux.We ship the equivalent onWindows and OS X) Modulo glue, the file system layer contains core functionality Data manager used for local persistent data caching and optimized remote object store fetches Metadata transport layer manages the MagFS control plane
  31. 31. Data Manager File System Layer SimplifiedWrite: Deduplication + Encryption Write Request Plaintext Variable-Length Chunking Encrypted Text (E) AES-256 (K) Object Name (N) SHA-256 Local Cache Remote Transfer Encryption Key (K) SHA-256
  32. 32. Very simple example! In reality, most operations are not synchronous, are batched, and clients get ack early Incoming data is broken up into smaller variable-length chunks for deduplication Per-chunk encryption used where the per-chunk key is derived from a cryptographic hash of unencrypted data Chunk name derived from hash of encrypted data
  33. 33. Data Manager File System Layer SimplifiedWrite: Deduplication + Encryption Write Request Plaintext Variable-Length Chunking Encrypted Text (E) AES-256 (K) Object Name (N) SHA-256 <File, Offset, N, K> Optional(<URI>) Local Cache Remote Transfer <N, E> <URI, E> No Encryption Keys in the Cloud No Encryption Keys in Local Cache Encryption Key (K) SHA-256 <E>
  34. 34. Encrypted data (but not key) is written to local cache Write request with offset, chunk name, and encryption key is made to the server If new chunk, a secure write URI is sent to the client Data manager queues and writes chunk to the cloud No encryption keys in local cache or object store
  35. 35. Data Manager File System Layer Simplified Read: Deduplication + Encryption Read Request <File, Offset, Range> Local Cache Remote Transfer <N, URI> Encryption Key (K) <N, K, URI> Encrypted Text (E) <E> <URI> <E> <URI> <E> Plaintext AES-256 (K)
  36. 36. Another very simple example. Does not include metadata caching either. Server responds to a read request with the chunk name, decryption key, and secure read URI A local cache miss causes an object storage fetch. Encrypted chunk is decrypted using the server-provided key and unencrypted data returned to the application. All deduplication and encryption is always transparent to the application.
  37. 37. The Client in Real Life Does a Lot More! • File and Directory Leases (data and metadata caching) • Asynchronous Operations (including writes) • Operation Compounding • Runtime Optimizations (e.g., read ahead) • Optimizing for High Bandwidth Delay Product (BDP) • …
  38. 38. There is a separate discussion on leases later when we talk about how clients and servers optimize performance at runtime
  39. 39. Object Storage (public, on-premises,or hybrid) Data Metadata Metadata Servers Clients Communication Details Thrift (HTTPS) REST (HTTPS)
  40. 40. Important: Split Data and Metadata paths (always, not optional). Clients directly access the object store. MagFS does not need to scale the data plane. Client technically speaks REST over HTTPS to the object store but has no knowledge of the actual API (server- provided URIs) The MagFS protocol uses Thrift over HTTPS (firewall and proxy friendly). Enables efficient encoding and easy protocol extension without breaking compatibility.
  41. 41. Server Architecture
  42. 42. The next file slides cover how we virtualize file namespaces, the distributed system deployment, a view into internals, and a brief overview of leases
  43. 43. Metadata Server Internals Metadata Storage Layer Storage Core Backups Production Development GC Scrubbing Quotas Dedup Leases Security HA MagFS Ext. Sharing Multi-Cloud Versioning Offline Mode Cloud Abstraction Layer Legend
  44. 44. The metadata server internals have been modularized to provide both development and runtime agility For example, adding support for a new object storage system doesn’t impact the rest of the code Runtime background operations (e.g., hot backups, garbage collection, scrubbing) do not impact clients. The file system protocol is separate from file system- agnostic features (e.g., quotas, lease, and lock management)
  45. 45. Bootstrapping:Virtualized Namespaces server.example.comshare HOST FQDN FOLDER Legacy server.example.comshare MagFS Dynamic mapping to host:port
  46. 46. With both Window UNC paths or NFS server/share exports, the exported file system would be tied to a DNS name. Instead, MagFS virtualizes the access path. Nothing changes with respect to applications but a virtualized server:share combination can map to any host:port This is extremely useful for High Availability Failover and Disaster Recovery
  47. 47. Discovery Service Metadata Server Metadata Server (HA) Metadata Server ZooKeeper ZooKeeperZooKeeper Monitoring Management Console Config + Scheduler Virtual Filer  Host:Port Mapping
  48. 48. MagFS is a distributed system. It has a number of backend services:VM and Service Monitoring, ZooKeeper for server registration and discovery,Admin management console, job scheduler,AD integration, etc. Shares are deployed in HA or non-HA configuration. HA comes with automatic failover. Clients use a discovery service to map namespace to server
  49. 49. One of the big challenges in any distributed file system is the tradeoff between consistency and performance. In a naïve strongly consistent system, every operation needs to be centralized on a server.This is obviously bad for performance. The MagFS metadata server therefore hands leases out to clients for data and metadata caching (including caching writes and updates)
  50. 50. Leases: Performance and Strong Consistency Read Write HandleLeaseTypes Read Read + Handle Read + Write + Handle Lease States Valid File Leases Valid Directory Leases
  51. 51. Lease Types: READ allows client to cache reads locally, WRITE allows local write caching, and HANDLE where files can be closed and reopened locally Valid Lease Type combinations are: READ, READ + HANDLE, READ + WRITE + HANDLE. Others don’t really apply (e.g,WRITE is exclusive and READ + HANDLE come for free if a WRITE lease is held) MagFS also supports WRITE directory leases
  52. 52. Cloud Storage Interaction
  53. 53. While Maginatics does not provide an Object Storage system itself, it works with a number of different products.The next few slides will talk about the challenges of interoperating with a large number of systems as well the technical challenges of layering a file system on top of them.
  54. 54. Object Storage (public, on-premises,or hybrid)
  55. 55. Today, MagFS supports a large number of object storage systems: private and public Swift and Atmos deployments,AWS S3, public and private S3 clones, Azure, and others not mentioned here We are seeing an increasing shift towards vendors providing S3 and Swift API compatibility layers even if they originally had their own REST-style protocols
  56. 56. Object Storage systems are like snowflakes!
  57. 57. MagFS also works hard to address inter-object store variance and hide the complexity from the end user. MagFS uses very basic API calls (GET/PUT/DELETE object/bucket and Signed URLs) and we discovered a number of differences in vendor implementations MagFS also optimizes data layout for different object stores to obtain the best performance. For example, data layout on S3,Atmos, and Swift differs to match the underlying platform.
  58. 58. Object Store API Compatibility Q: Has anyone come across a near 100% Amazon S3 API compatible object storage system? A: It is hard to find a near-100% compatible product… -Vendor w/ S3 Compatible Product
  59. 59. Even vendors claiming to support the same API have differences, bugs, or interpretation differences. For example, most S3 compatible systems we have added support is different from one another (e.g., subsets of API supported, differing API interpretations, bugs, etc.). Swift is similar.The same code cannot be used with a generic Swift setup and the public cloud providers that are based on Swift. Swift authentication (Keystone, TempAuth, etc.) also differs between vendors.
  60. 60. Object Storage (public, on-premises,or hybrid) Data Metadata Metadata Servers Clients Direct Client Access: Security Problem?
  61. 61. One of the challenges with providing clients direct object store access is security.There is generally one (or few) master API key(s) that can delete or read arbitrary data. However, as different MagFS users have different access rights to files, we should not provide the master key to clients (even though the data is encrypted). Further, a malicious client would be able to wipe all data with the master key!
  62. 62. Request Signing
  63. 63. The solution to providing secure and time-limited data access to clients is to use Request Signing, a feature found in all mature object storage systems today. The next few slides will walk through an example of how Request Signing works for a write.
  64. 64. Server-Driven Request Signing SignString = HTTP-Verb + "n" + Content-MD5 + "n" + Content-Type + "n" + Date + "n" + Resource + "n" + ...
  65. 65. Client read or write requests are authorized by the MagFS server that shares the master key with the object storage system Signing is done by the metadata server creating a request string in a pre-defined order
  66. 66. Server-Driven Request Signing SignString = PUT + "n" + Content-MD5 + "n" + Content-Type + "n" + Date + "n" + Resource + "n" + ...
  67. 67. The first component of the signature string is the HTTP verb used.This would be GET for a read and generally PUT for a write (some providers like Atmos use POST). DELETEs are never performed by the client.
  68. 68. Server-Driven Request Signing SignString = PUT + "n" + 07BzhNET7exJ6qYjitX/AA== + "n" + Content-Type + "n" + Date + "n" + Resource + "n" + ...
  69. 69. The second component is a cryptographic hash of the data.A number of object storage systems will reject data whose cryptographic hash doesn’t match the request.This is useful to protect against TCP errors that the TCP checksum doesn’t catch, buggy clients, and even malicious clients. A common hash algorithm used at this step is MD5 but some object storage systems are now supporting stronger cryptographic algorithms
  70. 70. Server-Driven Request Signing SignString = PUT + "n" + 07BzhNET7exJ6qYjitX/AA== + "n" + image/jpeg + "n" + Date + "n" + Resource + "n" + ...
  71. 71. The next component is the content-type of the object. We are using the JPEG type in this example but, in MagFS, this would be “application/octet-stream” for all our objects as they are encrypted binary data.
  72. 72. Server-Driven Request Signing SignString = PUT + "n" + 07BzhNET7exJ6qYjitX/AA== + "n" + image/jpeg + "n" + Tue, 11 Jun 2013 00:27:41 + "n" + Resource + "n" + ...
  73. 73. Following the content-type, we now add a timestamp field.This is very useful because it puts a time limit on this request to prevent replay attacks. Most object stores place a reasonable time limit on request validity (e.g., 15 minutes) but a number also allow configurable values. MagFS supports both.
  74. 74. Server-Driven Request Signing SignString = PUT + "n" + 07BzhNET7exJ6qYjitX/AA== + "n" + image/jpeg + "n" + Tue, 11 Jun 2013 00:27:41 + "n" + /container/example.jpeg + "n" + ...
  75. 75. The final component in this example is the resource name and this includes both the container name and the object name within the container More options are possible in signature strings and these options differ from provider to provider
  76. 76. Server-Driven Request Signing SignString = PUT + "n" + 07BzhNET7exJ6qYjitX/AA== + "n" + image/jpeg + "n" + Tue, 11 Jun 2013 00:27:41 + "n" + /container/example.jpeg + "n" + ... HMAC-SHA1( , SignString)
  77. 77. Following the construction of the signature string, a keyed hash message authentication code (HMAC) is generated using the signature string and the master key This is a one-way transform and obtaining the HMAC value does not leak information about the master key
  78. 78. Server-Driven Request Signing SignString = PUT + "n" + 07BzhNET7exJ6qYjitX/AA== + "n" + image/jpeg + "n" + Tue, 11 Jun 2013 00:27:41 + "n" + /container/example.jpeg + "n" + ... Signature = Base64(HMAC-SHA1( , SignString))
  79. 79. A Base64 encoded representation (signature) of this HMAC is sent to the client to prove that this request was authorized by the server
  80. 80. Object Storage (public, on-premises,or hybrid) Data Metadata Metadata Servers Clients Safe Direct Client Access via Request Signing 1. Read/Write Request 3. HTTP Request + Signature + Encrypted Data 2. HTTP Request + Signature
  81. 81. To summarize, read or write operations not serviced from the local cache requires server authorization Using the server-provided request and signature, a client can safely read and write data but only for the specified object The object store recalculates the signature based on the request, compares it to the received signature, and reject the request in case of a mismatch (e.g., wrong HTTP verb, stale/old request, swapped object names)
  82. 82. Dealing with Lost Client Writes • Clients can lose connectivity or, in the worst case, be malicious • Naïvely trusting client writes can “corrupt” w/ global dedup • MagFS server scrubs all writes: • Client acknowledges write • Server verifies object existence (object store performed MD5 at PUT) • Server can also read and verify object data (stronger SHA-256 check) • The object will be available for deduplication only after scrubbing
  83. 83. MagFS exposes global deduplication and therefore needs to handle buggy or malicious clients that might have claimed to have written data but did not The server therefore waits for a client to acknowledge the write, checks the object store to verify that the object was written (implies success for the cryptographic hash check), and can optionally scrub the data using a stronger cryptographic hash. Modulo optimizations for the same client (really user), the data is only used for deduplication after scrubbing.
  84. 84. Handling Object Store Eventual Consistency • Treat objects as immutable (even if modifications are allowed) • Use content-based names (generated using cryptographic hashes) • Tombstone names after Garbage Collection • Suffix generation number to content-based names in case of resurrection
  85. 85. Some object stores have eventually consistent properties and can lead to interesting read-after-write behaviors where what you read might not be the most recent write. To address this, we treat all objects as immutable, use content-based names, and using a suffix-based method to tombstone names so that they are never reused AWS S3 supporting read-after-first-put consistency in most regions also really helps with the above scheme
  86. 86. Security Architecture
  87. 87. In theory, this is where we would discuss MagFS’s security architecture. However, as you observed, security is baked into the product at every level and has been covered throughout the deck.We will therefore only recap here.
  88. 88. Recap: On-Premises Security Model • User authentication and permissions derived from native Active Directory setup • Encryption keys are never exposed to the cloud • Data and metadata is always encrypted:At-Rest and In-Flight
  89. 89. Quick point about Active Directory (AD):The fact that all our user permissions, group membership information, and other authentication information is derived from AD makes it very simple for admins and using MagFS does not change their workflows.
  90. 90. Slides (with speaker notes) at Try MagFS at