Hot Swap - Software RAID

Objective

If one of the disks on your server is failing, you can hot-swap it if you have a compatible top-range model.

Find out the main steps for hot-swapping a disk on a server with a software RAID configuration.

Requirements

an mHG, HG or BHG server
a software RAID (with an LSI card)
SSH (Linux) or RDP (Windows) access
the "sas2ircu" utility (use the Broadcom search engine to find it).

Instructions

On Linux

Step 1: Identify the disk concerned

To illustrate the purpose of this guide, we assume that we have received an alert for the/dev/sdb disk. The disk is defective, and we want to hot-swap it. Please adapt the details of this guide according to your specific situation.

To begin, test and check the Serial Number of the disk concerned.

root@ns3054662:/home# smartctl -a /dev/sdb
>>> smartctl 6.4 2014-10-07 r4002 [x86_64-linux-3.14.32-xxxx-grs-ipv6-64] (local build)
>>> Copyright (C) 2002-14, Bruce Allen, Christian Franke, www.smartmontools.org

>>> === START OF INFORMATION SECTION ===
>>> Vendor:               HGST
>>> Product:              HUS726040ALS210
>>> Revision:             A907
>>> Compliance:           SPC-4
>>> User Capacity:        4,000,787,030,016 bytes [4.00 TB]
>>> Logical block size:   512 bytes
>>> LB provisioning type: unreported, LBPME=0, LBPRZ=0
>>> Rotation Rate:        7200 rpm
>>> Form Factor:          3.5 inches
>>> Logical Unit id:      0x5000cca25d3155bc
>>> Serial number:        K4GW439B
>>> Device type:          disk
>>> Transport protocol:   SAS (SPL-3)
>>> Local Time is:        Mon Nov 21 14:23:43 2016 CET
>>> SMART support is:     Available - device has SMART capability.
>>> SMART support is:     Enabled
>>> Temperature Warning:  Enabled

>>> === START OF READ SMART DATA SECTION ===
>>> SMART Health Status: OK

>>> Current Drive Temperature:     34 C
>>> Drive Trip Temperature:        85 C

>>> Manufactured in week 44 of year 2016
>>> Specified cycle count over device lifetime:  50000
>>> Accumulated start-stop cycles:  9
>>> Specified load-unload count over device lifetime:  600000
>>> Accumulated load-unload cycles:  14
>>> Elements in grown defect list: 0

>>> Vendor (Seagate) cache information
>>> Blocks sent to initiator = 2305525022720

>>> Error counter log:
>>>        Errors Corrected by           Total   Correction     Gigabytes    Total
>>>            ECC          rereads/    errors   algorithm      processed    uncorrected
>>>        fast | delayed   rewrites  corrected  invocations   [10^9 bytes]  errors
>>> read:          0        572         0       22548         77          4.725         5580
>>> write:         0        0         0         19548       196         17.344          2569

>>> Non-medium error count:        0

>>> SMART Self-test log
>>> Num  Test              Status                 segment  LifeTime  LBA_first_err [SK ASC ASQ]
>>>  Description                              number   (hours)
>>> # 1  Background short  Completed                   -       6                 - [-   -    -]
>>> # 2  Background short  Completed                   -       4                 - [-   -    -]
>>> # 3  Background short  Completed                   -       4                 - [-   -    -]
>>> # 4  Background short  Completed                   -       4                 - [-   -    -]
>>> # 5  Background short  Completed                   -       1                 - [-   -    -]

>>> Long (extended) Self Test duration: 34237 seconds [570.6 minutes]

Here, you will note that:

the "SDB" disk has failed due to uncorrected errors
its Serial Number corresponds to the alert received (via the datacentre or any other monitoring tool)

To get only the Serial Number:

root@ns3054662:/home# smartctl -a /dev/sdb | grep Serial
>>> Serial number:        K4GW439B

Step 2: Retrieve the disk’s position

You must now find the Slot ID and the Enclosure ID of the disk concerned. To do this, use the «sas2ircu» tool already installed on the server.

Then start by checking that the disks are properly connected via an LSI card.

root@ns3054662:/home# lspci | grep -i LSI
>>> 81:00.0 Serial Attached SCSI controller: LSI Logic / Symbios Logic SAS2004 PCI-Express Fusion-MPT SAS-2 [Spitfire] (rev 03)

If this is the case, determine the ID of this LSI card.

root@ns3054662:/home# ./sas2ircu list
>>> LSI Corporation SAS2 IR Configuration Utility.
>>> Version 5.00.00.00 (2010.02.09)
>>> Copyright (c) 2009 LSI Corporation. All rights reserved.

>>>          Adapter      Vendor  Device                       SubSys  SubSys
>>>  Index    Type          ID      ID    Pci Address          Ven ID  Dev ID
>>>  -----  ------------  ------  ------  -----------------    ------  ------
>>>      0     SAS2004     1000h    70h   00h:81h:00h:00h      1000h   3010h
>>> SAS2IRCU: Utility Completed Successfully.

The index corresponds to the ID. Here, the card has the index/ID 0.

With this information, now retrieve for the disk concerned (via its Serial Number): the Slot ID and the Enclosure ID.

root@ns3054662:/home# ./sas2ircu 0 display | grep -B 7 -A 2 K4GW439B
>>> Device is a Hard disk
>>>   Enclosure                               : 1
>>>   Slot                                    : 3
>>>   State                                   : Available (AVL)
>>>   Manufacturer                            : HGST
>>>   Model Number                            : HUS726040ALS210
>>>   Firmware Revision                       : A907
>>>   Serial No                               : K4GW439B
>>>   Protocol                                : SAS
>>>   Drive Type                              : SAS_HDD

This command is used to obtain the disk information, including the Serial Number, which is the K4GW439B here.

In our example, we retrieved the Enclosure ID (corresponding to 1) and the Slot ID (corresponding to 3).

Stage 3: Switch on the disk

Using the information retrieved during the previous steps, turn on the LED of the faulty disk, and replace it with the command ./sas2ircu 0 locate EncID:SlotID on. Customise it to suit your situation, as per the example below:

root@ns3054662:/home# ./sas2ircu 0 locate 1:3 on
>>> LSI Corporation SAS2 IR Configuration Utility.
>>> Version 5.00.00.00 (2010.02.09)
>>> Copyright (c) 2009 LSI Corporation. All rights reserved.

>>> SAS2IRCU: LOCATE Command completed successfully.
>>> SAS2IRCU: Command LOCATE Completed Successfully.
>>> SAS2IRCU: Utility Completed Successfully.

You can disable the disk flashing, by replacing "on" with "off" in the command.

Step 4: Remove the defective disk from the RAID

If you have not already done so, switch the defective disk to Faulty. Then look at the RAID status.

root@ns3054662:/home# cat /proc/mdstat
>>> Personalities : [linear] [raid0] [raid1] [raid10] [raid6] [raid5] [raid4] [multipath] [faulty]
>>> md2 : active raid1 sda2[0] sdb2[1]
>>>       3885385728 blocks super 1.2 [2/2] [UU]
>>>       bitmap: 0/29 pages [0KB], 65536KB chunk

>>> md1 : active raid1 sdb1[1] sda1[0]
>>>       20971456 blocks [2/2] [UU]

>>> unused devices: <none>

In this example, the defective disk is part of md1 and md2 (sdb1 and sdb2). We will therefore change this one to Faulty, respectively sdb1 in md1 and sdb2 in md2.

root@ns3054662:/home# mdadm --manage /dev/md1 --set-faulty /dev/sdb1
>>> mdadm: set /dev/sdb1 faulty in /dev/md1

root@ns3054662:/home# mdadm --manage /dev/md2 --set-faulty /dev/sdb2
>>> mdadm: set /dev/sdb2 faulty in /dev/md2

once you have made these changes, check the RAID status again.

root@ns3054662:/home# cat /proc/mdstat
>>> Personalities : [linear] [raid0] [raid1] [raid10] [raid6] [raid5] [raid4] [multipath] [faulty]
>>> md2 : active raid1 sda2[0] sdb2[1](/ca/en/dedicated/hotswap-raid-soft/F)
>>>       3885385728 blocks super 1.2 [2/1] [U_]
>>>       bitmap: 0/29 pages [0KB], 65536KB chunk

>>> md1 : active raid1 sdb1[2](/ca/en/dedicated/hotswap-raid-soft/F) sda1[0]
>>>       20971456 blocks [2/1] [U_]

>>> unused devices: <none>

The sdb1 and sdb2 have been switched to faulty (F). You can now remove the disk from the RAID.

root@ns3054662:/home# mdadm --manage /dev/md1 --remove /dev/sdb1
>>> mdadm: hot removed /dev/sdb1 from /dev/md1

root@ns3054662:/home# mdadm --manage /dev/md2 --remove /dev/sdb2
>>> mdadm: hot removed /dev/sdb2 from /dev/md2

Finally, check that the disk is no longer present.

root@ns3054662:/home# cat /proc/mdstat
>>> Personalities : [linear] [raid0] [raid1] [raid10] [raid6] [raid5] [raid4] [multipath] [faulty]
>>> md2 : active raid1 sda2[0]
>>>       3885385728 blocks super 1.2 [2/1] [U_]
>>>       bitmap: 0/29 pages [0KB], 65536KB chunk

>>> md1 : active raid1 sda1[0]
>>>       20971456 blocks [2/1] [U_]

>>> unused devices: <none>

The defective disk is now ready to be replaced by a datacentre technician. Once the operation is complete, you just have to resync the RAID. To do this, you can use the following guide: Configuring software RAID

On Windows

Step 1: Identify the disk

It is important to launch the command terminal as an administrator, so that you do not receive any errors.

To begin, test and check the Serial Number of the disk concerned. In the screenshot below, the storage is not really defective, but we will act as if it were.

Here, you will note that:

the "SDB" disk has failed due to uncorrected errors
its Serial Number corresponds to the alert received (via the datacentre or any other monitoring tool)

Step 2: Retrieve the disk’s position

You will now need to find the Slot ID and the Enclosure ID of the disk concerned. To do this, use the «sas2ircu» tool already installed on the server.

Start by determining the ID of this LSI card.

Our LSI card has the index/ID “0”.

With this information, now retrieve for the disk concerned (via its Serial Number): the Slot ID and the Enclosure ID.

You can use this command to retrieve the disk information, including the Serial Number, which is K4G187WB here.

In our example, we have retrieved the Enclosure ID (corresponding to 1) and the Slot ID (corresponding to 1).

Stage 3: Switch on the disk

Using the information retrieved during the previous steps, turn on the LED of the faulty disk, and replace it with the command .\sas2ircu 0 locate EncID:SlotID on. Customise it to suit your situation, as per the example below: