Andrew Gauljclouds PMC

Apache jclouds at Maginatics

Experiences with billions of blobs across many blobstore providers.

Agenda

• What is blob storage

• Blobstore compatibility

• Case study: Maginatics Cloud Storage Platform (MCSP)

• Scaling

• Lessons learned

• Future directions

• Conclusion

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http://jclouds.apache.orghttps://maginatics.com

What is blob storage?

Blobstores offer key-value storage that is:

• Scalable: 10s TB with few nodes and 100s of PB with thousands of nodes

• Inexpensive: built on commodity hardware

• Available/durable: tolerates hardware failures

Do not offer guarantees that block storage and file systems provide:

• Limited interface: get, put, delete

• Eventual consistency: blob reads may return stale or no data for some limited time

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jclouds supports many providers

Multiple public and private implementations allow customer trade-offs.

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Public Object Storage Private Object Storage

Blobstore compatibility

jclouds abstracts differences between APIs, but semantic differences remain:

• Atmos: cannot overwrite blob

• AWS-S3: cannot mutate or append to a blob, cannot put blob without explicit size

• Swift: eventually consistent

Portable applications must use the lowest-common denominator functionality:

• Write to blobs exactly once, never mutate or append

• Can read from blobs at any time, but must retry due to eventual consistency

• When deleting, never reuse blob name

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Maginatics Cloud Storage Platform (MCSP)

• Virtualized, cloud-based storage system

• Layers network file system semantics on top of blob storage

• Run any application on a variety platforms, including multiple-client file sharing

• MCSP is a cloud-optimized NAS filer

• Smart client gives LAN performance over WANs

• Flexible deployment options: public, private, hybrid cloud

• Refer to SNIA SDC 2013 slides for technical background

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Scaling Throughput

MCSP supports thousands of clients reading and writing simultaneously.

Single server could become a bottleneck, especially smaller instance sizes.

Instead vend signed URLs to clients to allow them direct access to blobstore:

• Cryptographically signed URLs allow read or write access to a specific blob for a specified time

• Can embed other properties like content length and hash

This technique allows a single MCSP server to mediate many Gbit/s throughput!

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Scaling Number of Blobs

MCSP manages 100 TB of blob data across 1 billion blobs.

Some providers require specific naming or sharding for best performance:

• Atmos: no more than 100,000 blobs per directory, shard across directories

• AWS-S3: name blob with unique prefixes

• Swift: no more than 1 million blobs per container, shard across containers

• GCS & HPC: remove Expect: 100-continue

• Other quirks: Cleversafe performs better when disabling container listing

Surprisingly challenging workload: removing all blobs from a large container.

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Scaling Blob Sizes

Most MCSP blobs have small sizes, but some use cases require larger ones.

jclouds support up to 2 GB blobs across all blobstores:

• Could support 5 GB with Java 7

AWS-S3, Azure, and Swift support multi-part upload, tested with 40 GB blobs:

Large blobs increase chances of transient network errors and failures:

• Use a repeatable Payload like ByteSource to allow jclouds to retry

• Always include MD5 checksum to guarantee data integrity

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Lessons Learned

Cross-provider support required substantial effort:

• Long tail of issues with authentication, configuration, error codes, timeouts, etc.

• S3- and Swift-compatible clones are like snowflakes, no two are alike

Measuring performance is difficult:

• Blob naming and sharding important

• Public providers will reshard very active containers for better performance

• Private blobstores require configuration and tuning

Mock blobstores (filesystem and transient) helped testing.

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Future Directions

More diagnostic tools, especially for private blobstores.• Maginatics will contribute benchmark tool and compatibility

testerModernize with Guava additions, e.g., ByteSource, Hashing, MediaType.Simplify implementation:• De-async?• Remove annotations?New providers:• Modernized Swift (in-progress)• Google Cloud Storage (GSoC 2014?)• Amazon Glacier• Joyent Manta?

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Recap

• jclouds can provide portability between blobstore providers if your application does not strongly depend on blobstoresemantics

• Applications can scale with the correct architecture and implementation choices

• More work to do to make jclouds an inviting platform for all Java developers

• jclouds community helped Maginatics over the last three years and we look forward to continuing to contribute

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Thank you.

http://jclouds.apache.org

https://maginatics.com

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