Frequently Asked Questions

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151. How do the different types of storage compare to each other?

This is an illustration how how the different types of storage that is available compare to each other regarding Availability, Reliability, Performance and Price.

Reliability
High reliability means a low risk of data loss over a long period of time.
Availability
High availability means the system is (almost) always online and in order to do this it has to handle equipment failures of different kinds and still be running.
Performance
Performance may both mean high IOPS (many small requests) and bandwidth (lots of data), but here it is simplified.
Price
This is the cost in SEK per terabyte of stored data per year. (Updated in December 2015.)

One of many things that are beyond this comparison is the cost of entry. A single big PC-server with a lot of disk is around 250 kSEK and can store 576 TB raw data (around half of that is usable when using 3+2 RAID6 plus hot spares) and may last with support for around 5 years. A small share on the HNAS file server, which may be useful for a whole department storing small but important files, may be as low as 1 TB and cost 7000 SEK/year. A Ceph system is only recommended if one is scaling it up to a lot of file servers (and a lot of time for system administration) providing huge amount of bandwidth.

In practice this means that a PC file server, with proper backup or remote snapshotting to another PC file server, may be useful for storing a lot of data cheaply, but not for example used as 24/7 available file storage.

The university HNAS file server service is a very good for general storage of data in a safe way.

Availability-Performance comparison The performance in the HNAS system and a PC with SSDs is great, but HNAS is a lot more available since it has fault-tolerant hardware to higher extent.

Reliability-Price comparison There is a very small risk of data loss in a well set up PC file server with backups. The same applies to the HNAS system, although it is more expensive and as seen above, more available.

This entry storage.different was last modified 2016-06-23

This documentation is covered by GNU Free Documentation License.