Dell PowerEdge XE2420 EMC PowerEdge RAID Controller S140 Users Guide - Page 16

Background Array Scan, Checkpointing, Virtual disk cache policies

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Background Array Scan Verifies and rectifies correctable media errors on mirror, volume, or parity data for virtual disks. Background array scan (BAS) starts automatically after a virtual disk is created while in the Windows operating system. Checkpointing Allows different types of checkpointing to resume at the last point following a restart. After the system restarts, background checkpointing resumes at its most recent checkpoint. Three types of checkpointing are available: • Consistency Check (CC) • Background Initialization (BGI) • Rebuild Consistency check Consistency check (CC) is a background operation that verifies and corrects the mirror or parity data for fault-tolerant physical disks. It is recommended that you periodically run a consistency check on the physical disks. By default, CC corrects mirror or parity inconsistencies. After the data is corrected, the data on the primary physical disk in a mirror set is assumed to be the correct data and is written to the secondary physical disk mirror set. The CC operation reports data inconsistencies through an event notification. A CC cannot be user-initiated in the BIOS configuration utility, accessed using Ctrl + R. However, CC can be initiated using OpenManage Server Administrator Storage Management. For more information, see the OMSA user's guide at www.dell.com/openmanagemanuals. Background initialization Background initialization (BGI) of a redundant virtual disk creates the parity data that allows the virtual disk to maintain its redundant data and survive a physical disk failure. Similar to CC, BGI helps the controller to identify and correct problems that might occur with the redundant data at a later time. CAUTION: Data is lost if a physical disk fails before the completion of a BGI operation. BGI allows a redundant virtual disk to be used immediately. NOTE: Although a BGI is software-initiated from within the BIOS Configuration Utility (accessible through Ctrl + R), the PERC S140 drivers must be loaded before the BGI runs. Automatic virtual disk rebuild Rebuilds a redundant virtual disk automatically when a failure is detected if a hot spare is assigned for this capability. Virtual disk cache policies NOTE: Configuring virtual disk cache policies on NVMe PCIe SSD is not supported. The PERC S140 uses part of system memory for cache. It supports the following cache options: • Read Ahead/Write Back • No Read Ahead/Write Back • Read Ahead/Write Through • No Read Ahead/Write Through Table 6. Read, Write, and Cache Policy for the PERC S140 Category Supported by S140 controller Cache settings Yes Read Ahead/Write Back Yes 16 Virtual Disks

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Background Array Scan
Verifies and rectifies correctable media errors on mirror, volume, or parity data for virtual disks. Background array scan (BAS) starts
automatically after a virtual disk is created while in the Windows operating system.
Checkpointing
Allows different types of checkpointing to resume at the last point following a restart. After the system restarts, background
checkpointing resumes at its most recent checkpoint.
Three types of checkpointing are available:
•
Consistency Check (CC)
•
Background Initialization (BGI)
•
Rebuild
Consistency check
Consistency check (CC) is a background operation that verifies and corrects the mirror or parity data for fault-tolerant physical disks. It is
recommended that you periodically run a consistency check on the physical disks.
By default, CC corrects mirror or parity inconsistencies. After the data is corrected, the data on the primary physical disk in a mirror set is
assumed to be the correct data and is written to the secondary physical disk mirror set.
The CC operation reports data inconsistencies through an event notification. A CC cannot be user-initiated in the BIOS configuration
utility, accessed using Ctrl + R. However, CC can be initiated using OpenManage Server Administrator Storage Management. For more
information, see the OMSA user’s guide at
www.dell.com/openmanagemanuals
.
Background initialization
Background initialization (BGI) of a redundant virtual disk creates the parity data that allows the virtual disk to maintain its redundant data
and survive a physical disk failure. Similar to CC, BGI helps the controller to identify and correct problems that might occur with the
redundant data at a later time.
CAUTION:
Data is lost if a physical disk fails before the completion of a BGI operation.
BGI allows a redundant virtual disk to be used immediately.
NOTE:
Although a BGI is software-initiated from within the BIOS Configuration Utility (accessible through Ctrl + R), the
PERC S140 drivers must be loaded before the BGI runs.
Automatic virtual disk rebuild
Rebuilds a redundant virtual disk automatically when a failure is detected if a hot spare is assigned for this capability.
Virtual disk cache policies
NOTE:
Configuring virtual disk cache policies on NVMe PCIe SSD is not supported.
The PERC S140 uses part of system memory for cache. It supports the following cache options:
•
Read Ahead/Write Back
•
No Read Ahead/Write Back
•
Read Ahead/Write Through
•
No Read Ahead/Write Through
Table 6. Read, Write, and Cache Policy for the PERC S140
Category
Supported by S140 controller
Cache settings
Yes
Read Ahead/Write Back
Yes
16
Virtual Disks