Hardware
A Server
Check out Von Neumann
The Von Neumann architecture points out 3 parts of a server: Memory, CPU and Disk/IO.
Memory for execution.
CPU for processing.
Disk & I/O for persistency.
Memory
Fast. Performant. 25x faster than an SSD.
DBs are designed around memory.
Disk-to-ram oriented dbs have been happening in recent years. The continued lowering cost of ram makes this appealing, due to ram's performance improvements.
In memory...
- aggregation
- index traversing
- writes
- first in ram
- query engine
- retrieves query results
- connections
- ~1MB per connection
More ram === more performance.
CPU
- Storage Engine
- WiredTired relies heavily on CPU
- Concurrency Model
- Mongo tries to use all cpu cores
- Non-Blocking operations use cpu: the more the better -
- writing different docs concurrently
- responding to query requests (reads)
- page compression
- data calculation
- agg operations
- map reduce
Disks
Mongo can use several types of disks.
This cal allow distributing IO load of DBs, indexes, journaling and log files across drives.
Types of disks affect performance. IOPS - input/output operations per sec. The higher the IOPS, the faster the performance of the mongo system.
| Type | IOPS |
|---|---|
| 7200 RMP SATA | ~75 - 100 |
| 15000 RMP SATA | ~175 - 210 |
| SSD Intel X25-E (SLC) | ~5000 |
| Amazon EBS Provisioned | Up to 2000 |
| FusionIO | ~135K |
Disks and Raid
Recommended raid for Mongo is Raid 10.
More redundancy with good performance.
Discourage raid 5 & raid 6. These do not provide sufficient performance.
Avoid Raid 0. Provides good write, but not high availability.
Blocking Ops
Not ALL write/reads are non-blocking.
Same-doc writing will block other writes.
Networking
The faster and the larger the bandwidth, the better performance will be experienced.
Replica sets help with high availability.
Different hosts that hold different nodes of the db can affect the overall system.
How far apart, geographically, the cluster nodes are also matters.
Load balancers, firewalls, and switches all interact with network speeds.
Concerns: Write Concerns, Read Concerns, and read preferences all matter as well.