Support for hybrid enclosures

ESS supports hybrid enclosures that comprise four or two enclosures containing only hard disk drives (HDDs) and one or two enclosures of only solid state drives (SSDs).

There are three hybrid enclosure models that are supported. The support for GH14S and GH24S is added in ESS 5.3.1. Start of change

The support for GH12S is added in ESS 5.3.1.1 End of change

GH14S

1 2U24 (SSD) and 4 5U84 (HDD) enclosures

GH14S recovery groups (RGs)

Each of the two GH14S RGs have a 12-disk SSD user declustered array (DA) and a 167-disk HDD user DA.

GH24S

2 2U24 (SSD) and 4 5U84 (HDD) enclosures

GH24S recovery groups

Each of the two GH24S RGs have a 24-disk SSD user DA and a 167-disk HDD user DA.

GH12S

1 2U24 (SSD) and 2 5U84 (HDD) enclosures

GH12S recovery groups

Each of the two GH14S RGs have a 12-disk SSD user DA and an 83-disk HDD user DA.

For information about 2U24 and 5U84 enclosures, see IBM ESS Expansion documentation.

For more information about hybrid enclosures, see:

Hybrid enclosure cabling information
Hybrid enclosure support in gssgenvdisks

Hybrid enclosure cabling information

Figure 1. GH14S cabling diagram

Figure 2. GH24S cabling diagram

Hybrid enclosure support in gssgenvdisks

The gssgenvdisks command can detect hybrid enclosures. In case of hybrid enclosures, the gssdgenvdisks command requires two declustered arrays (DAs). One DA comprises HDDs only and the other one comprises SSDs only.

gssgenvdisks provides a default placement policy in case hybrid enclosures are used. According to this policy, any data vdisk is placed on the DA which is composed of HDDs only and any metadata vdisk is placed on the DA which is composed of SSDs only.

In the following example, DA1 consists of HDDs and DA2 consists of SSDs. This example shows that the default data vdisk is placed in DA1 and the metadata vdisk is placed in DA2.

# gssgenvdisks --create-vdisk --create-nsds --create-filesystem --verbose \
--contact-node essio41 --filesystem-name gpfs0 --reserved-space-percent 1
...
...
# mmlsvdisk
                                                                   declustered     block size
 vdisk name                   RAID code        recovery group      array           in KiB      remarks
 ------------------           ---------------  ------------------  -----------     ----------  -------
 rg_io41_ce_Data_16M_2p_1     8+2p             rg_io41-ce          DA1               16384
 rg_io41_ce_Data_16M_2p_2     8+2p             rg_io41-ce          DA1               16384
 rg_io41_ce_MetaData_1M_3W_1  3WayReplication  rg_io41-ce          DA2                1024
 rg_io41_ce_loghome           4WayReplication  rg_io41-ce          DA1                2048     log
 rg_io41_ce_logtip            2WayReplication  rg_io41-ce          NVR                2048     logTip
 rg_io41_ce_logtipbackup      Unreplicated     rg_io41-ce          SSD                2048     logTipBackup
 rg_io42_ce_Data_16M_2p_1     8+2p             rg_io42-ce          DA1               16384
 rg_io42_ce_Data_16M_2p_2     8+2p             rg_io42-ce          DA1               16384
 rg_io42_ce_MetaData_1M_3W_1  3WayReplication  rg_io42-ce          DA2                1024
 rg_io42_ce_loghome           4WayReplication  rg_io42-ce          DA1                2048     log
 rg_io42_ce_logtip            2WayReplication  rg_io42-ce          NVR                2048     logTip
 rg_io42_ce_logtipbackup      Unreplicated     rg_io42-ce          SSD                2048     logTipBackup

You can override the default vdisk placement policy used in case of a hybrid enclosure system, by using the --use-only-da option. If the --use-only-da option is used, only the specified DA is considered for the vdisk creation. If the system is a hybrid enclosure and there are multiple DAs, the DAs available in the recovery group are not considered except for the one specified with the --use-only-da option.

You can create vdisks on other DAs using the BM Spectrum Scale RAID command.