HP E200 manual Replacing hard drives, Effects of a hard drive failure

Page 24

Effects of a hard drive failure

When a hard drive fails, all logical drives that are in the same array are affected. Each logical drive in an array can use a different fault-tolerance method, so each logical drive can be affected differently.

•RAID 0 configurations cannot tolerate drive failure. If any physical drive in the array fails, all non- fault-tolerant (RAID 0) logical drives in the same array will also fail.

•RAID 1+0 configurations can tolerate multiple drive failures as long as no failed drives are mirrored to one another.

•RAID 5 configurations can tolerate one drive failure.

Compromised fault tolerance

If more hard drives fail than the fault-tolerance method allows, fault tolerance is compromised, and the logical drive fails. In this case, all requests from the operating system are rejected with unrecoverable errors. You are likely to lose data, although it can sometimes be recovered (refer to "Recovering from compromised fault tolerance" on page 24).

One example of a situation in which compromised fault tolerance may occur is when a drive in an array fails while another drive in the array is being rebuilt. If the array has no online spare, any logical drives in this array that are configured with RAID 5 fault tolerance will fail.

Compromised fault tolerance can also be caused by non-drive problems, such as a faulty cable or temporary power loss to a storage system. In such cases, you do not need to replace the physical drives. However, you may still have lost data, especially if the system was busy at the time that the problem occurred.

Recovering from compromised fault tolerance

If fault tolerance is compromised, inserting replacement drives does not improve the condition of the logical volume. Instead, if the screen displays unrecoverable error messages, perform the following procedure to recover data:

1.Power down the entire system, and then power it back up. In some cases, a marginal drive will work again for long enough to enable you to make copies of important files.

If a 1779 POST message is displayed, press the F2 key to re-enable the logical volumes. Remember that data loss has probably occurred and any data on the logical volume is suspect.

2.Make copies of important data, if possible.

3.Replace any failed drives.

4.After you have replaced the failed drives, fault tolerance may again be compromised. If so, cycle the power again. If the 1779 POST message is displayed:

a.Press the F2 key to re-enable the logical drives.

b.Recreate the partitions.

c.Restore all data from backup.

To minimize the risk of data loss that is caused by compromised fault tolerance, make frequent backups of all logical volumes.

Replacing hard drives

The most common reason for replacing a hard drive is that it has failed. However, another reason is to gradually increase the storage capacity of the entire system.

Replacing, moving, or adding hard drives 24

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Contents HP Smart Array E200 Controller User Guide Audience assumptions Contents Diagnosing array problems Hardware features Controller specificationsBoard components Cache on Overview of the installation procedure Installing the controller in an unconfigured serverInstalling the controller in a previously configured server Overview of the installation procedure Installing the controller hardware Before beginning the installation Preparing the serverInstalling the controller board Connecting storage devices Updating the firmware Methods for updating the firmwareConfiguring an array IntroductionComparing the utilities Using Orca Select Create Logical DriveUsing ACU Using CpqonlinExpanding an array Migrating RAID level and stripe size online Setting the boot controller and controller order Setting a controller as the boot controllerSetting the controller order Installing device drivers and Management Agents Installing device driversInstalling Management Agents Replacing a battery Upgrading or replacing controller optionsUpgrading the cache Upgrading or replacing controller options Replacing, moving, or adding hard drives Identifying the status of a hard driveRecognizing hard drive failure Terminate the current operation and cause data lossReplacing hard drives Effects of a hard drive failureHard drive replacement guidelines Time required for a rebuild Upgrading hard drive capacity Moving drives and arrays Adding drivesReplacing, moving, or adding hard drives Diagnosing array problems Controller board runtime LEDsBattery pack LEDs LEDDiagnostic tools ADUElectrostatic discharge Preventing electrostatic dischargeGrounding methods to prevent electrostatic discharge Regulatory compliance notices European Union regulatory noticeBsmi notice Korean class B notice Battery replacement notice Taiwan battery recycling noticeAcronyms and abbreviations Index Status lights, battery pack
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