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allow support for parity '0', '1' enabling support for 2,3 drive setups (#15171)

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allows for further granular setups

- 2 drives (1 parity, 1 data)
- 3 drives (1 parity, 2 data)

Bonus: allows '0' parity as well.
This commit is contained in:
Harshavardhana
2022-06-27 20:22:18 -07:00
committed by GitHub
parent b7c7e59dac
commit 9c605ad153
17 changed files with 82 additions and 76 deletions
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2
docs/distributed/DESIGN.md
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@@ -41,7 +41,7 @@ Expansion of ellipses and choice of erasure sets based on this expansion is an a
- Erasure coding used by MinIO is [Reed-Solomon](https://github.com/klauspost/reedsolomon) erasure coding scheme, which has a total shard maximum of 256 i.e 128 data and 128 parity. MinIO design goes beyond this limitation by doing some practical architecture choices.
- Erasure set is a single erasure coding unit within a MinIO deployment. An object is sharded within an erasure set. Erasure set size is automatically calculated based on the number of disks. MinIO supports unlimited number of disks but each erasure set can be upto 16 disks and a minimum of 4 disks.
- Erasure set is a single erasure coding unit within a MinIO deployment. An object is sharded within an erasure set. Erasure set size is automatically calculated based on the number of disks. MinIO supports unlimited number of disks but each erasure set can be upto 16 disks and a minimum of 2 disks.
- We limited the number of drives to 16 for erasure set because, erasure code shards more than 16 can become chatty and do not have any performance advantages. Additionally since 16 drive erasure set gives you tolerance of 8 disks per object by default which is plenty in any practical scenario.

11
docs/distributed/README.md
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@@ -8,7 +8,7 @@ MinIO in distributed mode can help you setup a highly-available storage system w
### Data protection
Distributed MinIO provides protection against multiple node/drive failures and [bit rot](https://github.com/minio/minio/blob/master/docs/erasure/README.md#what-is-bit-rot-protection) using [erasure code](https://docs.min.io/docs/minio-erasure-code-quickstart-guide). As the minimum disks required for distributed MinIO is 4 (same as minimum disks required for erasure coding), erasure code automatically kicks in as you launch distributed MinIO.
Distributed MinIO provides protection against multiple node/drive failures and [bit rot](https://github.com/minio/minio/blob/master/docs/erasure/README.md#what-is-bit-rot-protection) using [erasure code](https://docs.min.io/docs/minio-erasure-code-quickstart-guide). As the minimum disks required for distributed MinIO is 2 (same as minimum disks required for erasure coding), erasure code automatically kicks in as you launch distributed MinIO.
If one or more disks are offline at the start of a PutObject or NewMultipartUpload operation the object will have additional data protection bits added automatically to provide additional safety for these objects.
@@ -22,9 +22,12 @@ Refer to sizing guide for more understanding on default values chosen depending
### Consistency Guarantees
MinIO follows strict **read-after-write** and **list-after-write** consistency model for all i/o operations both in distributed and standalone modes. This consistency model is only guaranteed if you use disk filesystems such as xfs, ext4 or zfs etc.. for distributed setup.
MinIO follows strict **read-after-write** and **list-after-write** consistency model for all i/o operations both in distributed and standalone modes. This consistency model is only guaranteed if you use disk filesystems such as xfs, zfs or btrfs etc.. for distributed setup.
**In our tests we also found ext4 does not honor POSIX O_DIRECT/Fdatasync semantics, ext4 trades performance for consistency guarantees. Please avoid ext4 in your setup.**
**If MinIO distributed setup is using NFS volumes underneath it is not guaranteed MinIO will provide these consistency guarantees since NFS is not strictly consistent (If you must use NFS we recommend that you atleast use NFSv4 instead of NFSv3 for relatively better outcomes).**
**If MinIO distributed setup is using NFS volumes underneath it is not guaranteed MinIO will provide these consistency guarantees since NFS is not consistent filesystem by design (If you must use NFS we recommend that you atleast use NFSv4 instead of NFSv3).**
## Get started
@@ -41,7 +44,7 @@ To start a distributed MinIO instance, you just need to pass drive locations as
**NOTE:**
- All the nodes running distributed MinIO should share a common root credentials, for the nodes to connect and trust each other. To achieve this, it is **recommended** to export root user and root password as environment variables, `MINIO_ROOT_USER` and `MINIO_ROOT_PASSWORD`, on all the nodes before executing MinIO server command. If not exported, default `minioadmin/minioadmin` credentials shall be used.
- **MinIO creates erasure-coding sets of _4_ to _16_ drives per set. The number of drives you provide in total must be a multiple of one of those numbers.**
- **MinIO creates erasure-coding sets of _2_ to _16_ drives per set. The number of drives you provide in total must be a multiple of one of those numbers.**
- **MinIO chooses the largest EC set size which divides into the total number of drives or total number of nodes given - making sure to keep the uniform distribution i.e each node participates equal number of drives per set**.
- **Each object is written to a single EC set, and therefore is spread over no more than 16 drives.**
- **All the nodes running distributed MinIO setup are recommended to be homogeneous, i.e. same operating system, same number of disks and same network interconnects.**