FS System: Understanding Hot Spare Coverage

Asset ID:	1-79-2000558.1
Update Date:	2018-02-10
Keywords:

Solution Type Predictive Self-Healing Sure

Solution 2000558.1 : FS System: Understanding Hot Spare Coverage

Applies to:

Oracle FS1-2 Flash Storage System - Version All Versions to All Versions [Release All Releases]
Information in this document applies to any platform.

Purpose

This document explains the details of hot spare coverage in the FS1-2.

Details

Spare coverage is different for Hard Disk Drives and Solid State Drive Drive Enclosures

Hard Disk Drive Disk Enclosures Dynamic Spare

The HDD Disk Enclosure (DE) uses dynamic spare for RAID 5 and RAID 10, by using unallocated strips on high-capacity hard disk drives (HDDs) in a given drive group. This spare capacity is striped across all of the HDDs in the drive group. Dynamic spares are used to support the RAID 5 protection level and the RAID 10 protection level. Dynamic spares cannot cross drive group boundaries.

In other words, there is no dedicated hot spare on the SAS DE as each drive has dedicated strips to rebuild data from parity (or copy strips for RAID 10) in case of a disk failure.

Solid State Drive Disk Enclosure Spare Drive

The SSD Disk Enclosure (DE) uses a floating spare drive for RAID 5 and the RAID 10.

The number of drives in an SSD DE is a factor of 6 plus the floating spare drive. Each group of 6 SSD drives is a Drive Group. The spare drive shows up as "unused" and is shared by all Drive Groups in the DE. If an SSD drive fails, the data is reconstructed to the spare. When the failed drive is replaced, it then becomes the spare drive for the DE. No copy-back is done. If a second failure occurs after reconstruction is complete but before the initial drive is replaced, the system will use it's parity data to continue functioning until the drive failures are replaced.

Available Drive Enclosures

Capacity DE (DE2-24C)

For available Hardware please visit Oracle System Handbook.

Notes:

Zeroing is only performed in manufacturing on new DEs not FRUs.
The FS System performs zeroing on FRUs, thus, allowing the use of the same FRU part numbers for both ZS and FS DEs.

Performance DE (DE2-24P)

For available Hardware please visit Oracle System Handbook.

Note: DE’s with SSD’s are offered in arrays of 6 drives + a hot spare so 7, 13 and 19 drive options
SSD drives can be field upgraded in blocks of 6

Layout of HDDs in the 24-Drive Enclosures

There are 2 arrays (drive groups) of 12 drives.

There is no dedicated hot spare for RAID 5 or 10 – it is made up out of rotating strips

Each stripe is like a traditional RAID group and that these stripes rotate the parity around the array with each new stripe.

Single Parity: Stores the original user data plus one set of parity bits to help in the recovery of lost data. Access to the data is preserved even after the failure of one drive. Single parity is implemented using "RAID 5" technology and is the default redundancy level for the Storage Classes that specify the performance-type media.
Mirroring: A RAID level in which the Oracle FS System maintains an exact duplicate of a logical volume at a different location. No parity data is used. Mirroring protects against the loss of at least one drive and possibly more drives with an improvement of the performance of random write operations. Mirrored RAID is implemented using "RAID 10"

Double Parity

Stores the original user data plus two sets of parity bits to help in the recovery of lost data. Access to the data is preserved even after the simultaneous failure of two drives. Double parity is implemented using "RAID 6" technology and is the default redundancy level for the Storage Classes that specify the capacity-type media.

This is the layout of hard disk drives in the 24 drive enclosures

There are 4 RAID types that exist on spinning media

RAID C is used to store the system configuration information and there is a copy on each drive
RAID 5S and RAID 10S has a rotating hot strip
RAID 6 replaces the option for ‘double redundant’ LUNs as two drives can fail in the array before redundancy is degraded. When a drive fails, some drives strips will copy, some will rebuild and some will just become spares

Inhibit Single Parity for Capacity Disk Storage Classes

Beginning with Version 6.2.0, Oracle FS System prevents the creation of volumes with single parity (RAID 5) on the Capacity Disk Storage Classes. All new volumes are created with double parity (RAID 6) for added data protection in the event of a drive failure. Existing volumes created with single parity are not affected.

Reference:

Oracle FS1-2 Flash Storage System Customer Release Notes can be found in Oracle Storage Help Center.

New layout of strips with rotating hot spare

High Availability Reference can be found in Oracle Storage Help Center.

References

<NOTE:1684888.1> - FS System: How to Change the Mounting Bracket of a 1.6TB SSD Drive in an FS1-2 Drive Enclosure
<NOTE:1924371.1> - FS System: How to Remove and Replace Hard Disk Drive or Solid State Drive from an FS1-2 Drive Enclosure
<NOTE:2001248.1> - FS System: Understanding Drive Enclosure Disk Drive States

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