Memory function of RAID controller card.
1. If the LSISAS2208/LSISAS3108 RAID controller card is configured with a battery or supercapacitor, data is written into the cache first. When the data volume in the cache reaches its limit, data is written into hard disks in sequence, greatly improving the access speed of small files.
Cache is volatile storage. If it does not have a battery or supercapacitor, its data will be lost when the server is powered off. This may cause data inconsistency.
For example, when a data record is written into the database, the RAID controller card stores the data record in cache first. However, at that time, the data record has not been written onto hard disks. If the server is powered off at that time, the data record will be lost and cannot be found in the database when required. The database keeps searching for the data endlessly. In extreme conditions, the database may crash.
The battery or supercapacitor can prevent data loss in power failures. When a server is powered off unexpectedly, the batter or supercapacitor provides power to the RAID controller card.
2. If the LSISAS2208/LSISAS3108 RAID controller card does not have a battery or supercapacitor, data is directly written into hard disks.