Home > Storage > PowerMax and VMAX > Data Protection > Dell PowerMax: Reliability, Availability, and Serviceability > Drive sparing
PowerMaxOS supports Universal Sparing to automatically protect a failing drive with a spare drive. Universal Sparing increases data availability of all volumes in use without loss of any data capacity, transparently to the host, and without user intervention.
Drive health is monitored proactively for any indication that they may be trending toward failure. Drive-dependent codes detect and report indications of failing health. For example, conditions such as errors on blocks of NAND media, errors in DRAM buffer media, and controller check errors.
When PowerMaxOS detects a drive is failing, the data on the faulty drive is copied directly to a spare drive attached to the same engine. The failing drive is set as read-only while data is copied and written to the spare. The failing drive is made not ready after the spare is synchronized.
If the faulty drive stops responding to valid commands prior to spare synchronization, the drive is made not ready and the data is rebuilt onto the spare drive through the remaining RAID members. When the faulty drive is replaced, data is copied from the spare to the new drive. The spare drive becomes an available spare again after the new drive is synchronized.
PowerMax systems have one spare drive behind each engine. The spare drives reside in dedicated drive locations. The spare drive type is the same as the highest capacity and performance class as the other drives behind the engine.
Modern, solid-state drives have a longer life than spinning disks of the past and have advanced feedback mechanisms that allow for proactive sparing and replacement before a failure occurs. The PowerMax spare drive count requirement was determined after thorough analysis. There is no need to configure additional spare drives.
Solutions Enabler provides tools to view information related to spare drives in PowerMax arrays.
The symcfg list –v output reports total values for Configured Actual Disks, Configured Spare Disks and Available Spare Disks in the system.
The Number of Configured Actual Disks field reports only non-spare configured disks, and Number of Configured Spare Disks field reports only configured spare disks.
The following shows the command symcfg -sid <sid> list -v:
Symmetrix ID: 000197600XYZ (Local)
Time Zone : Eastern Standard Time
Product Model : PowerMax_8000
Symmetrix ID : 000197600XYZ
Microcode Version (Number) : 5978 (175A0000)
--------------------< TRUNCATED >-------------------------
Number of Configured Actual Disks : 64
Number of Configured Spare Disks : 2
Number of Available Spare Disks : 2
The symdisk list –dskgrp_summary –by_engine reports spare coverage information per Disk Group per Engine. The -detail and -v options will provide additional information.
The Total and Available spare disk counts for each Disk Group include both spare disks that are in the same Disk Group in the same Engine, as well as shared spare disks in another Disk Group in the same Engine that provide acceptable spare coverage. These shared spares are also included in the total disk count for each Disk Group in each Engine. Therefore, the cumulative values of all Disk Groups in all Engines in this output should not be expected to match the values reported by the symcfg list –v command that were described in the previous example.
Total Disk Spare Coverage percentage for a Disk Group is the spare capacity in comparison to usable capacity shown in the output.
The following shows the command symdisk -sid <sid> list –dskgrp_summary –by_engine:
Disk Hyper Usable Capacity Spare Coverage
------------------------ ------- ------------------- -----------------
Flgs Speed Size Total Total Avail
Grp Eng Cnt LT (RPM) (MB) Disk (%) (MB) Disk (%) Disk (%)
---- --- ---- ---- ----- ------- ---- --- ---------- ---- --- ---- ---
1 1 9 IE 0 29063 8 89 14880255 1 12 1 100
2 1 25 IE 0 29063 24 96 44640765 1 4 1 100
2 2 33 IE 0 29063 32 97 59521020 1 3 1 100
---- --- ----------
Total 64 97 119042040
Legend:
Disk (L)ocation:
I = Internal, X = External, - = N/A
(T)echnology:
S = SATA, F = Fibre Channel, E = Enterprise Flash Drive, - = N/A
Spare Coverage as reported by the symdisk list –v and symdisk show commands indicates whether the disk currently has at least one available spare; that is, a spare disk that is not in a failed state or already invoked to another disk.
The following shows the command symdisk -sid <sid> list –v:
Symmetrix ID : 000197600XYZ
Disks Selected : 66
Director : DF-1C
Interface : C
Target ID : 0
Spindle ID : 0
--------------------< TRUNCATED >-------------------------
Spare Disk : N/A
Spare Coverage : True