LSI 3ware SAS 9750-8i Guia do Utilizador descarregar pdf (Página 164)

Maintaining Units

152 3ware SATA+SAS RAID Controller Card Software User Guide, Version 10.0

About Initialization

For 3ware SATA RAID controllers, initialize means to put the redundant data

on the drives of redundant units into a known state so that data can be

recovered in the event of a disk drive failure. This is sometimes referred to as

background initialization or resynching, and does not erase user data.

Some RAID levels must be initialized for best performance. (For specifics,

see “Initialization of Different RAID Types” on page 153.) When these units

are created in the BIOS (through 3BM), you can choose to do a foreground

initialization, which will take place before the operating system has loaded, or

a background initialization, which allows you to put the unit in service

immediately, but will slow down the unit performance until it completes. You

can elect to cancel foreground initialization, put the units into service, and

have initialization run in the background, instead.

Foreground Versus Background Initialization

Initialization makes parity information valid. Foreground initialization does

this by simply writing zeroes to all the drives so that they all have the same

values, overwriting any existing data in the process. In contrast, background

initialization uses an algorithm to resynch the parity information on the drives

and does not rewrite existing data.

A foreground initialization can be run from the BIOS using 3BM. It clears all

existing data from the drives. Foreground initialization can take up to several

hours, depending upon the size of the unit. After foreground initialization

completes, you can start the operating system and units will perform at peak

efficiency.

If immediate access to the unit is important, select background initialization.

Background initialization will then start automatically within about 10

minutes. Background initialization (resynching) does not write zeroes to the

drives or harm your data. You can partition, format, and use the unit safely

while it is initializing. The unit is fully fault-tolerant while the initialization

takes place. That is, if the unit degrades before the initialization is complete,

the data will remain intact.

When initializing is done after booting to the operating system, the process of

initializing takes longer than it does if initialization is done by writing zeroes

to the unit in the BIOS. Consequently, it will be a longer period of time until

the performance of the unit is fully optimal.

Note: Drives that support the Write Same feature (SCT) can write to multiple drive

sectors at once, improving initialization time. To take advantage of this feature, all

the drives in the unit must support Write Same.

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LSI 3ware SAS 9750-8i Guia do Utilizador Página 164

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