ViPR 2.1 - Replace a Commodity disk

Table of Contents

Drive replacement planning

Describes an efficient strategy for periodic grooming of an ECS Appliance to replace FAILED and SUSPECT storage drives.

Note Image
To replace the node's main (non-storage) drives, contact EMC Customer Support for assistance.

This document makes a distinction between the terms "drive" and "disk." A drive is a physical spindle. A disk is a logical entity (that is, a partition on a drive).

When the system labels a drive as FAILED, the data protection logic rebuilds the data on that drive on other drives in the system. The FAILED drive no longer participates in the system in any way. Replacing a drive does not involve restoring any data to the replacement drive. Therefore, a FAILED drive only represents a loss of raw capacity to the system. This characteristic of the built-in data protection lessens the need for an immediate service action when a drive fails.

SUSPECT drives that are suspect because of physical errors, as opposed to connectivity issues, should also be replaced. When a drive is labeled SUSPECT, the system no longer writes new data to the drive, but the system will continue to read from it. The SUSPECT drive with physical errors will eventually be labeled FAILED when the physical errors exceed a certain threshold. While the drive remains SUSPECT, the drive is not participating fully in the storage system. Therefore, a disk on the corresponding drive should be manually set to Bad using the supplied cs_hwmgr command line tool. This step gives the system the opportunity to finish pending network interactions with the drive. Data on the drive will be reconstructed elsewhere in the system using copies of the data from other drives. Therefore, you can begin the replacement process as soon as the system indicates that the disk on the corresponding FAILED drive was successfully set to Bad.

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The ViPR UI lists a node as DEGRADED when the node has storage disks with the Suspect or Bad status.

An efficient way to handle FAILED drives is to replace them periodically. The replacement period should be calculated using the manufacturer's mean failure rate of the drives such that there is no danger that a critical number of drives can fail by the next planned service date. This process is called "grooming." Grooming involves:

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Output for the cs_hal list disks command

Describes the types of output rows from the cs_hal list disks command.

In the abbreviated cs_hal list disks output below, notice the different types of rows:

[root@layton-cyan ~]# cs_hal list disks
Disks(s):
SCSI Device Block Device Enclosure   Partition Name                      Slot Serial Number       SMART Status   DiskSet
----------- ------------ ----------- ----------------------------------- ---- ------------------- -------------- ------------
n/a         /dev/md0     RAID vol    n/a                                 n/a  not supported       n/a
/dev/sg4    /dev/sdb     internal                                        0    KLH6DHXJ            GOOD
/dev/sg5    /dev/sdc     internal                                        1    KLH6DM1J            GOOD
/dev/sg8    /dev/sdf     /dev/sg0    Object:Formatted:Good               A08  WCAW32601327        GOOD
/dev/sg9    /dev/sdg     /dev/sg0    Object:Formatted:Bad                A09  WCAW32568324        FAILED: self-test fail; read element;
/dev/sg10   /dev/sdh     /dev/sg0    Object:Formatted:Suspect            A10  WCAW32547329        SUSPECT: Reallocated_Sector_Count(5)=11
...
unavailable              /dev/sg0                                        E05    

   internal: 2
   external: 30

total disks: 32

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Replace drives

Replace FAILED and SUSPECT storage drives using commands on the node.

Note Image
Do not place the node in maintenance mode to replace drives.

Procedure

  1. Start an SSH session with the node that owns the FAILED or SUSPECT drives.
  2. Use the cs_hal list disks command and observe the drive health status of each drive in the SMART Status column:
    # cs_hal list disks
    Disks(s):
    SCSI Device Block Device Enclosure   Partition Name                      Slot Serial Number       SMART Status   DiskSet
    ----------- ------------ ----------- ----------------------------------- ---- ------------------- -------------- ------------
    n/a         /dev/md0     RAID vol    n/a                                 n/a  not supported       n/a
    /dev/sg4    /dev/sdb     internal                                        0    KLH6DHXJ            GOOD
    /dev/sg5    /dev/sdc     internal                                        1    KLH6DM1J            GOOD
    /dev/sg8    /dev/sdf     /dev/sg0    Object:Formatted:Good               A08  WCAW32601327        GOOD
    /dev/sg9    /dev/sdg     /dev/sg0    Object:Formatted:Good               A09  WCAW32568324        GOOD
    /dev/sg10   /dev/sdh     /dev/sg0    Object:Formatted:Good               A10  WCAW32547329        GOOD
    /dev/sg11   /dev/sdi     /dev/sg0    Object:Formatted:Good               B08  WCAW32543442        GOOD
    /dev/sg12   /dev/sdj     /dev/sg0    Object:Formatted:Good               B07  WCAW32499200        GOOD
    /dev/sg13   /dev/sdk     /dev/sg0    Object:Formatted:Good               B06  WCAW32540070        GOOD
    /dev/sg14   /dev/sdl     /dev/sg0    Object:Formatted:Good               A11  WCAW32493928        GOOD
    /dev/sg15   /dev/sdm     /dev/sg0    Object:Formatted:Good               B10  WCAW32612977        GOOD
    /dev/sg16   /dev/sdn     /dev/sg0    Object:Formatted:Suspect            B11  WCAW32599710        SUSPECT: Reallocated_Sector_Count(5)=11
    /dev/sg17   /dev/sdo     /dev/sg0    Object:Formatted:Good               C11  WCAW32566491        GOOD
    /dev/sg18   /dev/sdp     /dev/sg0    Object:Formatted:Good               D11  WCAW32528145        GOOD
    /dev/sg19   /dev/sdq     /dev/sg0    Object:Formatted:Good               C10  WCAW32509214        GOOD
    /dev/sg20   /dev/sdr     /dev/sg0    Object:Formatted:Good               D10  WCAW32499242        GOOD
    /dev/sg21   /dev/sds     /dev/sg0    Object:Formatted:Good               C09  WCAW32613242        GOOD
    /dev/sg22   /dev/sdt     /dev/sg0    Object:Formatted:Good               D09  WCAW32503593        GOOD
    /dev/sg23   /dev/sdu     /dev/sg0    Object:Formatted:Good               E11  WCAW32607576        GOOD
    /dev/sg24   /dev/sdv     /dev/sg0    Object:Formatted:Good               E10  WCAW32507898        GOOD
    /dev/sg25   /dev/sdw     /dev/sg0    Object:Formatted:Good               E09  WCAW32613032        GOOD
    /dev/sg26   /dev/sdx     /dev/sg0    Object:Formatted:Good               C08  WCAW32613016        GOOD
    /dev/sg27   /dev/sdy     /dev/sg0    Object:Formatted:Good               D08  WCAW32543718        GOOD
    /dev/sg28   /dev/sdz     /dev/sg0    Object:Formatted:Good               C07  WCAW32599747        GOOD
    /dev/sg29   /dev/sdaa    /dev/sg0    Object:Formatted:Good               E06  WCAW32612688        GOOD
    /dev/sg30   /dev/sdab    /dev/sg0    Object:Formatted:Good               E08  WCAW32567229        GOOD
    /dev/sg31   /dev/sdac    /dev/sg0    Object:Formatted:Good               D06  WCAW32609899        GOOD
    /dev/sg32   /dev/sdad    /dev/sg0    Object:Formatted:Good               C06  WCAW32546152        GOOD
    /dev/sg33   /dev/sdae    /dev/sg0    Object:Formatted:Good               D07  WCAW32613312        GOOD
    /dev/sg34   /dev/sdaf    /dev/sg0    Object:Formatted:Good               E07  WCAW32507641        GOOD
    /dev/sg3    /dev/sda     /dev/sg0    Object:Formatted:Good               A06  WCAW32547444        GOOD
    /dev/sg6    /dev/sdd     /dev/sg0    Object:Formatted:Good               A07  WCAW32525128        GOOD
    /dev/sg7    /dev/sde     /dev/sg0    Object:Formatted:Good               B09  WCAW32496935        GOOD
    …
    …
    unavailable              /dev/sg0                                        E02
    unavailable              /dev/sg0                                        E03
    unavailable              /dev/sg0                                        E04
    unavailable              /dev/sg0                                        E05
    
       internal: 2
       external: 30
    
    total disks: 32
    Here the report shows the 2 internal drives of the node, 30 storage drives (one of them in a SUSPECT health state), and 30 empty slots labeled as unavailable.
  3. Mark down the Slot ID and Serial Number of the FAILED or SUSPECT drive.
  4. Use the cs_hwmgr command to force the status of the disk on the corresponding SUSPECT drive to Bad. In the example above, the SUSPECT drive has a reallocated sector count that indicates the drive has physical failures and is a candidate for replacement.
    # cs_hwmgr ListDrives | grep WCAW32599710 
    ATA       HUS726060ALA640      WCAW32599710         6001      Suspect      B11       
    # cs_hwmgr SetDriveHealthToBad ATA HUS726060ALA640 WCAW32599710
  5. If the cs_hwgmr ListDrives | grep WCAW32599710 command does not return any output, then the drive is not being managed by the hwmgr tool. Stop and open a Support ticket to continue with the drive replacement.
  6. Use the cs_hwmgr RemoveDrive to remove/unallocate the drive from the default diskset. Note that this command does not remove the drive from the output of the cs_hwmgr ListDrives command.
    # cs_hwmgr RemoveDrive ATA HUS726060ALA640 WCAW32599710
  7. Use the cs_hal led command and the Serial Number or Slot ID to turn on the LED for the drive (to find the proper drive in the drawer). The two commands below are equivalent. The first uses the Serial Number and the second uses the Slot ID.
    # cs_hal led WCAW32599710 on
    
    # cs_hal led B11 on
  8. Following the instructions from your hardware manufacturer, locate the disk and replace it in the same slot.
  9. Use the cs_hal list disks command to confirm that the system recognizes the new drive. The new drive has the same Slot ID as the replaced drive. Take note of the new Serial Number. The system automatically integrates the new disk into use by the appropriate services.
  10. Use the cs_hal led command and the new Serial Number or Slot ID to turn off the LED for the drive.
    # cs_hal led <serial_number_of_new_drive> off
    
    # cs_hal led B11 off

Results

The node and system automatically detect the drive and initialize it for use.

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