- sharding strategy
- metadata storage
3 types of storage: block storage, file storage, object storage(blob=binary large object)
The unit of these 3 types:
- block storage: evenly sized chunks.
- file storage: a hierarchy of files in folders
- blob/object storage: immutable objects, e.g. images, audio or other multimedia objects; sometimes binary executable code is stored as a blob.
Online Transaction Processing Databases (OLTP)
- Facebook Graph, mission critical, strong consistency, core services
Semi-online Light Transaction Processing Databases (SLTP)
- Facebook Messages and Facebook Time Series
- Photos, videos, etc
- Data Warehouse, Logs storage
Facebook example. This is adapted from this slide
|Facebook Graph||MySQL/TAO||Random read IOPS||few ms||quickly consistent across data centers||no data loss|
|Messages and Time Series||HBase and HDFS||Write IOPS/storage capacity||< 200 ms||consistent within a data center||no data loss|
|Photos / Videos||Haystack||storage capacity||< 250 ms||immutable||no data loss|
|Data Warehouse||Hive / Presto / HDFS||storage capacity||< 1min||not consistent across data centers||no silent data loss|
- S3: object storage
- EBS: block storage
- EFS: file storage
- EBS: high latency(comparing to databases)
- EBS is mountable storage; it can be mounted as a device to an EC2 instance, NAS
- S3 not mountable, a storage service, not a device
- EBS can be thought of as external hard drive, while S3 is more akin to DropBox
- Glacier is S3 for archived files.
- Google Cloud Storage: object storage
- Google Cloud Filestore: file storage
- Persistent Disk: block storage
- Gluster: scalable file storage with object capabilities
Ceph: object first, scalable object storage with block and file capabilities.
- CephFS: a POSIX-compliant network file system
Ceph and Gluster are both SDS(Software-defined Storage). Ceph is for shorter-term stoarge and more frequent user access. Gluster should not be used for something transactional, like a database or something that depends on really strict locking.
Redhat recommends XFS, not ZFS.
Distributed file systems: GFS, Colossus, Alluxio, CephFS, HDFS
Cluster level, fault tolerant, distributed file systems:
- append only
- not for structured data(use database instead)
- not optimized for small files
- cluster level, not data center level, data destroyed after the cluster turns down
- HDFS is the open source version of GFS(Google File System)
- Colossus is the successor of GFS
- Spanner uses Colossus to store its tablets
- DAS: Directly Attached Storage.
- NAS: Network Attached Storage.