Improve some wording in disk caching docs (#5730)
Harshavardhana
7 years ago
committed by
Nitish Tiwari
parent
af024a9c69
commit
228c8f05f4
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# Disk Caching Design [](https://slack.minio.io) |
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This document explains some basic assumptions and design approach, limits of the disk caching feature. If you're looking to get started with disk cache, we suggest you go through the [getting started document](https://github.com/minio/minio/blob/master/docs/disk-caching/README.md) first. |
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## Command-line |
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``` |
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minio server -h |
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... |
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... |
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CACHE: |
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MINIO_CACHE_DRIVES: List of cache drives delimited by ";" |
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MINIO_CACHE_EXCLUDE: List of cache exclusion patterns delimited by ";" |
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MINIO_CACHE_EXPIRY: Cache expiry duration in days |
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... |
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... |
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7. Start minio server with edge caching enabled on '/drive1', '/drive2' and '/drive3', |
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exclude all objects under 'mybucket', exclude all objects with '.pdf' as extension |
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with expiry upto 40 days. |
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$ export MINIO_CACHE_DRIVES="/drive1;/drive2;/drive3" |
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$ export MINIO_CACHE_EXCLUDE="mybucket/*;*.pdf" |
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$ export MINIO_CACHE_EXPIRY=40 |
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$ minio server /home/shared |
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``` |
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## Assumptions |
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- Disk cache size defaults to 80% of your drive capacity. |
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- Disk caching requires [`atime`](http://kerolasa.github.io/filetimes.html) support to be enabled on the cache drive. |
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- Expiration of each cached entry takes user provided expiry as a hint, and defaults to 90 days if not provided. |
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- Garbage collection sweep of the expired cache entries happens whenever cache usage is > 80% of drive capacity, GC continues until sufficient disk space is reclaimed. |
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- An object is only cached when drive has sufficient disk space, upto 100 times the size of the object. |
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## Behavior |
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Disk caching caches objects for both **uploaded** and **downloaded** objects i.e |
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- Caches new objects for entries not found in cache while downloading. Otherwise serves from the cache. |
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- Caches all successfully uploaded objects. Replaces existing cached entry of the same object if needed. |
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- When an object is deleted, corresponding entry in cache if any is deleted as well. |
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- Cache continues to work for read-only operations such as GET, HEAD when backend is offline. |
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- Cache disallows write operations when backend is offline. |
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> NOTE: Expiration happens automatically based on the configured interval as explained above, frequently accessed objects stay alive in cache for a significantly longer time. |
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## Limits |
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- Bucket policies are not cached, so anonymous operations are not supported when backend is offline. |
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- Objects are distributed using deterministic hashing among the list of configured cache drives. If one or more drives go offline, or cache drive configuration is altered in any way, performance may degrade to a linear lookup time depending on the number of disks in cache. |
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@ -1,55 +1,41 @@ |
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## Disk based caching |
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# Disk Cache Quickstart Guide [](https://slack.minio.io) |
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Disk caching can be turned on by updating the "cache" config |
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settings for minio server. By default, this is at `${HOME}/.minio`. |
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Disk caching feature here refers to the use of caching disks to store content closer to the tenants. For instance, if you access an object from a lets say `gateway azure` setup and download the object that gets cached, each subsequent request on the object gets served directly from the cache drives until it expires. This feature allows Minio users to have |
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"cache" takes the drives location, duration to expiry (in days) and any |
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wildcard patterns to exclude certain content from cache as |
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configuration settings. |
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``` |
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- Object to be delivered with the best possible performance. |
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- Dramatic improvements for time to first byte for any object. |
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## Get started |
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### 1. Prerequisites |
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Install Minio - [Minio Quickstart Guide](https://docs.minio.io/docs/minio). |
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### 2. Run Minio with cache |
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Disk caching can be enabled by updating the `cache` config settings for Minio server. Config `cache` settings takes the drive locations, cache expiry duration (in days) and any wildcard patterns to exclude from being cached. |
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```json |
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"cache": { |
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"drives": ["/path/drive1", "/path/drive2", "/path/drive3"], |
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"expiry": 30, |
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"exclude": ["*.png","bucket1/a/b","bucket2/*"] |
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"drives": ["/drive1", "/drive2", "/drive3"], |
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"expiry": 90, |
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"exclude": ["*.pdf","mybucket/*"] |
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}, |
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``` |
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The cache settings can also be set by the environment variables |
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below. When set, environment variables override any cache settings in config.json |
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``` |
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The cache settings may also be set through environment variables. When set, environment variables override any `cache` config settings for Minio server. Following example uses `/drive1`, `/drive2` and `/drive3` for caching, with expiry upto 90 days while excluding all objects under bucket `mybucket` and all objects with '.pdf' as extension while starting a standalone erasure coded setup. |
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```bash |
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export MINIO_CACHE_DRIVES="/drive1;/drive2;/drive3" |
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export MINIO_CACHE_EXPIRY=90 |
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export MINIO_CACHE_EXCLUDE="pattern1;pattern2;pattern3" |
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export MINIO_CACHE_EXCLUDE="*.pdf;mybucket/*" |
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minio server /export{1...24} |
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``` |
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- Cache size is 80% of drive capacity. Disk caching requires |
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Atime support to be enabled on the cache drive. |
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- Expiration of entries takes user provided expiry as a hint, |
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and defaults to 90 days if not provided. |
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- Garbage collection sweep of the expired entries happens whenever |
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disk usage is > 80% of drive capacity until sufficient disk |
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space has been freed. |
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- Object is cached only when drive has sufficient disk space for 100 times the size of current object |
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### Behavior |
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Disk caching happens on both GET and PUT operations. |
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- GET caches new objects for entries not found in cache. |
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Otherwise serves from the cache. |
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- PUT/POST caches all successfully uploaded objects. Replaces |
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existing cached entry for the same object if needed. |
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When an object is deleted, it is automatically cleared from the cache. |
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NOTE: Expiration happens automatically based on the configured |
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interval as explained above, frequently accessed objects stay |
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alive in cache for a significantly longer time on every cache hit. |
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### 3. Test your setup |
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To test this setup, access the Minio server via browser or [`mc`](https://docs.minio.io/docs/minio-client-quickstart-guide). You’ll see the uploaded files are accessible from the all the Minio endpoints. |
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The following caveats apply for offline mode |
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- GET, LIST and HEAD operations will be served from the disk cache. |
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- PUT operations are disallowed when gateway backend is offline. |
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- Anonymous operations are not implemented as of now. |
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# Explore Further |
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- [Use `mc` with Minio Server](https://docs.minio.io/docs/minio-client-quickstart-guide) |
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- [Use `aws-cli` with Minio Server](https://docs.minio.io/docs/aws-cli-with-minio) |
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- [Use `s3cmd` with Minio Server](https://docs.minio.io/docs/s3cmd-with-minio) |
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- [Use `minio-go` SDK with Minio Server](https://docs.minio.io/docs/golang-client-quickstart-guide) |
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- [The Minio documentation website](https://docs.minio.io) |
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