Data center storage
Data center storage[edit]
The word "data" in data center is represented by storage technologies.Without considering the hardwares and softwares the difference between data centers is just about the information they have saved and generated.Permanent storage technologies and data processing always develop concurrently because they are strongly related.and have a direct impact on applications performance.[1]
Data storage technologies have seperated into classes based on their rules and their charachteristics,these classes are:
- Primary storage: Also representedd as memory is a storage mechanism that can be directly accessed by CPU or central processing unit.these kinds of memory have small capacity compared to other storage technologies but much faster.[1]
- Secondary storage: Secondary storage or auxiliary memory, cannot be accessed directly by CPU ,these devices have input and output channels to transfer information to primary storage.These storage devices have more capacity than primary storage and provide slower access times.[1]
- Tertiary storage or removable mass storage media provide much longer access time than previous memory but they are low cost per data unit and have more capacity and can provide capacity for long-term data sets.[1]
Disk Array[edit]
Without considering the technology which is used,hard drives are used as a secondary storage today.However data on internal disk of servers are only used in the hardware failure case.and it is clear that data centers need more than single storage device for corporate data centers.The difference between hard drives and server is about two devices :JBODs(Just a Bunch Of Disks)or disk arrays.JBODs are basically hard drives aggregated in a single unit that can be accessed by remote application servers.Because each server has the duty of controlling its assigned HDDs,JBODs cannot be corresponded with level of managment and availability which server provider facilities need.[1] a disk array is including multiple disks which can be used as a scalable shared resource among application environments a disk array mainly composed of:
- Controllers: administers disks or other array hardware resources and organize the server access to data by its subjected device.[1]
- Access port: Interface using for exchanging data with servers.[1]
- Cache: RAM or random access memory and also referred as flash memory which being used make I/O operations faster to store.It can be at controller and expansion modules.[1]
- Disk enclosure: HDDs and SSDs could be located on it usually similar disk drives from characteristically view.
- Redundant power supplies[1]
Tape drives and libraries[edit]
Magnetic tapes are storage medium which are made of thin plastic film with a magnetizable cover.[2]
Before the time that hard disks become popular,these types of storage device were used as a secondary storage technology in computer rooms.Nowadays they are still used by data centers as tertiary storage because they are cheep and long lasting.[1]
For using these storage devices first the library robot must find the location of correct tape and move it to tape driver and after that pass the tape head on the demanded data, it can take minutes to retrieve data from a computer system and that's why it is slower than hard disk drives.[1]
Modern tape libraries have the capacity of saving 100 petabytes and their major sellers are IBM and Oracle. and they have capability of data encryption and tape lifecycle management and mainly are used for backups and archiving.[1]
References[edit]
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