User Guide

Organize the physical disk drives in arrays after the drives are connected to PERC 2/DC, formatted, and initialized. Each array can consist of one to eight physical disk drives (and up to 16 drives when used with the Span feature.)

PERC 2/DC supports up to eight arrays. The number of drives in an array determines the RAID levels that can be supported.

You must arrange the arrays to provide additional organization for the drive array. You must arrange arrays so that you can create system drives that can function as boot devices.

You can sequentially arrange arrays with an identical number of drives so that the drives in the group are spanned. Spanned drives can be treated as one large drive. Data can be striped across multiple arrays as one logical drive.

You can create spanned drives by using the PERC 2/DC BIOS Configuration utility or the PERC Configuration Manager.

Any drive that is present, formatted, and initialized but is not included in a array or logical drive is automatically designated as a hot spare.

You can also designate drives as hot spares via PERC 2/DC BIOS Configuration utility, the PERC Configuration Manager, or PERC Console.

Logical drives are arrays or spanned arrays that are presented to the operating system. You must create one or more logical drives. The logical drive capacity must include all of the disk space in an array. If an array with drives with mixed sizes, the smallest common size is used and larger disk drives are truncated. The logical drive capacity can also be larger than an array by using spanning. PERC 2/DC supports up to 8 logical drives.

The most important factors in RAID array configuration are: drive capacity, drive availability (fault tolerance), and drive performance. You cannot configure a logical drive that optimizes all three factors, but it is easy to choose a logical drive configuration that maximizes one factor at the expense of the other two factors, although needs are seldom that simple.

RAID 0 achieves maximum drive capacity, but does not provide data redundancy. Maximum drive capacity for each RAID level is shown below. OEM level firmware that can span up to 4 logical drives is assumed.

You can maximize the availability of data on the physical disk drive in the logical array by maximizing the level of fault tolerance. The levels of fault tolerance provided by the RAID levels are:

You can configure an array for optimal performance. However, optimal drive configuration for one type of application will probably not be optimal for any other application. A basic guideline of the performance characteristics for RAID drive arrays at each RAID level is:

Only one RAID level can be assigned to each logical drive. The drives required per RAID level is:

After you have installed the PERC 2/DC controller in the server and have attached all physical disk drives, perform the following actions to prepare a RAID disk array:

Each type of data stored in the disk subsystem has a different frequency of read and write activity. If you know the data access requirements, you can more successfully determine a strategy for optimizing the disk subsystem capacity, availability, and performance.

Servers that support Video on Demand typically read the data often, but write data infrequently. Both the read and write operations tend to be long. Data stored on a general-purpose file server involves relatively short read and write operations with relatively small files.

You must first define the major purpose of the disk array. Will this disk array increase the system storage capacity for general-purpose file and print servers? Does this disk array support any software system that must be available 24 hours per day? Will the information stored in this disk array contains large audio or video files that must be available on demand? Will this disk array contain data from an imaging system?

You must identify the purpose of the data to be stored in the disk subsystem before you can confidently choose a RAID level and a RAID configuration.

Answer the following questions about this array:

The following table lists the possible RAID levels, fault tolerance, and effective capacity for all possible drive configurations for an array consisting of one to eight drives. This table does not take into account any hot spare (standby) drives. You should always have a hot spare drive in case of drive failure. RAID 1 requires two drives.