The Nexsan E-Series and BEAST enterprise class storage systems are capable of being configured with multiple simultaneous RAID levels. The traditional RAID levels of 0, 1, 1+0, 4, 5 and 6 are supported, as well as the Nexsan unique levels Accelerated RAID 5S and 6S where parity is stored on dedicated SSD(s) to improve random write IOP performance. Also, different drive types can be intermixed within a system. Supported drive types are 7,200 rpm SAS hard disks and 1WPD TLC Solid State Disks (SSD) as well as QLC SSD for highly affordable solid state performance. These drives are also offered as SED (self-encrypting drives). This enables the storage array to be tailored to meet multiple application and budget requirements.
For example, applications where the data is constantly being read and updated such as a CRM systems, online transactional databases, and applications such as payroll and HR, the storage needs to perform well for random small block writes. Whereas for backup applications or web pages that are static nature and can be viewed but not altered, the storage system must perform well in a sequential and caching modes. A single storage system that concurrently supports multiple RAID levels and different drive types allows the investment to be maximized, as well as simplifying the management of the storage environment.
Regardless of the RAID level or drive type, all writes are cached, the write acknowledgement sent to the server and the data aggregated for efficient writing to disk. The battery-protected write cache is mirrored between the two controllers to protect the writes in the event of a controller failure. Writes are also automatically flushed to disk in event of a power failure. Read cache is used to pre-fetch data from the drives during sequential read operations to make read requests faster.
RAID Levels Explained
RAID 0
RAID level 0 provides data striping. Blocks of data from each file are spread out across multiple disk drives. This improves the speed of both read and write operations, but does not provide fault tolerance. The advantage of using the E-Series or BEAST in RAID 0 vs a traditional JBOD device is that cache in the controllers can be utilized to improve the read and write performance. RAID 0 is ideal for temporary or scratch space and should not be used for critical data.
RAID 1
RAID level 1 is a 2 drive RAID group where data is written identically data to each drive. If one drive fails, the other drive still contains the data. RAID 1 provides fast read performance with fault tolerance, but write performance may be degraded as each write require two writes to complete. Data such as static web pages, data mining, operating system or data that is non alterable or minimally altered are good candidates for RAID 1.
RAID 10
RAID level 10 is a combination of RAID levels 0 and 1. Data is both striped and mirrored. RAID level 10 is used whenever an even number of drives (minimum of four) is selected for a RAID 1 array. RAID 10 is ideal for applications with transactional small random IO workloads such as database servers, as data is both mirrored and striped providing excellent redundancy and performance.
RAID 5
RAID level 5 provides data striping at the byte level and also stripe error correction information. Parity data, instead of being stored on only one disk, is distributed among all disks in the array. RAID 5 is best suited for general purpose workloads or those requiring high transactional IO such as CRM application or databases.
RAID 6
RAID level 6 provides block level data striping with parity data distributed across all disks. For additional redundancy, each block of parity data exists on two disks in the array instead of only one. Sequential applications such as video streaming, video capture and backups that are sequential in nature are ideal candidates for RAID 6.
Nexsan Accelerated RAID levels
RAID levels RAID5S and RAID 6S are similar to RAID5 and RAID 6 providing the equivalent level of parity protection but utilize SSDs for storing the parity vs striping the parity across the spinning disk drives within the RAID array. This significantly improves the random write performance of the RAID array compared to traditional disk drives.
RAID5S/RAID6S have consistent performance over time and regardless of the working data set size, as compared to caching/tiering solutions where performance may be severely impacted during data reorganization or when the high-performance buffers become full.
RAID level 5S provides the same level of protection as RAID 5 but uses a solid-state disk to store parity with all data is striped across the hard disk drives within the RAID array.
RAID level 6S provides the same level of protection as RAID 6 but uses two solid state disks to store parity and all data is striped across the hard disk drives within the RAID array.