Seagate Corvault Configuration
Seagate Corvault Setup with QuantaStor
This guide describes how to integrate a Seagate Corvault system with QuantaStor in a high-availability (HA) configuration using SAS connectivity.
The Corvault system presents logical volumes to QuantaStor which are then used just like any other JBOD connected HDD except that the virtual devices (LUNs) from the Corvault are typically larger such as 60TB, 80TB or 100TB in size.
Supported Connectivity
Seagate Corvault units are always connected to QuantaStor using SAS ports and cabling. You can use one or two connections per Corvault to each QuantaStor server. If you do two connections you must have at least two SAS HBAs in the QuantaStor with SAS HBA1 connecting to IO Module 1 in the Corvault and SAS HBA2 connecting to IO Module 2 in the Corvault.
Single-Path Connectivity
Single path connectivity will provide 48Gb (4x SAS lanes at 12Gb) of throughput to the Corvault which will deliver about 5GB/sec. We generally recommend going with a multi-path configuration but if your cluster is connecting to a large number of Corvaults such as 8x or 10x then you may not have enough SAS ports across your HBAs to connect to them all twice to enable multi-pathing. In those cases single-path is fine.
Multipath-Path Connectivity
Multipath connectivity is the preferred way to connect your Corvaults to the QuantaStor storage servers. Note how HBA1 connects to each IO Module (IOM) and HBA2 also connects to both IOMs. This is important as it ensures connectivity in the event of an IOM failure. This is also important due to the way QuantaStor does IO fencing via SCSI3 Persistent Reservations (WERO mode).
Architecture Overview
Corvault operates as a dual-controller active/active array that internally uses Seagate's ADAPT erasure coding to provide fault-tolerance and durability in the event of one or more device failures.
Seagate Corvault Configuration
QuantaStor has integrated support for configuration and monitoring of the Corvault units. To enable this first navigate to the Controllers & Enclosures section of the WUI then click the button to Add External System. In there you'll input the IP address and the username and password to your Corvault system in order for QuantaStor to add it to the Storage Grid.
Seagate Corvault Disk Group (DG) and Pool Creation
The Corvault units have a concept of a DG and a Pool but in practice these are generally one-to-one with each DG being used by a single pool. We recommend dividing the Corvault into two ADAPT Pools with 53x HDDs per pool when using 4U106 Corvaults and with 42x HDDs per pool when using the 5U84 Corvaults. When creating a pool you'll get the opportunity to select a ADAPT layout, we generally use the 16k+2m layout as that provides the most capacity with 88% usable. Note also that you'll need to allocate at least one virtual hot-spare in each Corvault Pool, we generally set this to 2x virtual spares per Pool. Note that this is not a specific drive that's a spare as the data is distributed across all the drives in an ADAPT pool but when a drive fails this virtual spare's worth of space will be used to fully repair the Pool to 100%. In many cases we find that the ADAPT pools are already configured when the system arrives. If you see that there are two ADAPT pools in 16k+2m layout already configured on your system then you can skip this step and move onto logical volume creation.
Logical Volume Creation
The first thing to consider is how many logical volumes (LUNs) to create per ADAPT pool. Making more LUNs will generally improve performance and concurrency as the filesystems (OpenZFS, Ceph) will be able to send more IO concurrently when you have more devices. This is because more devices equals more VDEVs in scale-up configurations and more OSDs in scale-out configurations. In practice we recommend dividing up each ADAPT pool into 16, 24, or 32x LUNs. QuantaStor makes this easy when you create the logical volumes via QuantaStor as it will automatically calculate the maximum size for the volumes in order to use up all the available space in the ADAPT pool.
- Note - In scale-up configurations using many Corvaults (eg 10x) you'll want something like 16x LUNs per ADAPT pool in order to keep the device count under 500. 500 devices isn't a hard limit but device count can impact boot speed and failover speed and fewer devices per pool makes it easier to manage.
- Note - In scale-out configurations note that more OSDs means more RAM and CPU requirements. Generally speaking, allocate 1.5GHz and 4GB of RAM to each OSD. So choosing 32x LUNs per ADAPT pool will require about double the CPU and RAM as going with 16x LUNs per ADAPT pool but it will also roughly double the performance.
- Note - For very large scale-out configurations fewer LUNs per Corvault translates to greater scalability. For example, 100x Corvaults each delivering 32x LUNs equates to 3200x OSDs in the cluster. Keeping your scale-out clusters under 4000 OSDs will make them easier to manage.
Volume Assignment & Discovery
When you create your Corvault logical volumes via the QuantaStor External Systems module it will also allow you to assign those to specific QuantaStor hosts. QuantaStor will automatically take care of configuring the volume to SAS host address for you within the Corvault units. After they've been assigned navigate to the Physical Disks section in the QuantaStor WUI then:
- Navigate to Storage System → Physical Disks.
- Click Rescan Disks.
- Verify Corvault LUNs appear as new block devices.
Summary
The Seagate Corvault units can be thought of as smart JBODs as they have a layer of fault-tolerance and durability built-in. This built-in durability does not negate the need for having fault-tolerance at the QuantaStor level. We recommend choosing at minimum a single parity layout (RAIDZ1, with RAIDZ2 recommended) in scale-up configurations and a double-parity layout (EC 4k+2m) at minimum in scale-out configurations.