Generic Storage System Architecture

The above diagram shows a generic stand-alone storage system architecture, where a storage OS is installed over a bare metal server and thus making it a storage server. Here I am using an enterprise class storage OS named Open-E DSS V7 which is installed on a Dell PowerEdge R720xd. R720xd can have up to twelve 3.5" drives at the front plus two 2.5" drives at the rear. Here in the diagram, the last 2 disks (Disk Group03) are 2.5" drives installed at the rear and being used as OS drive in RAID1. Apart from that we have five SAS 7.2K and 15K disks that are grouped into two RAID groups. Comparing the disk IOPS 'Disk Group01' can be considered fast and 'Disk Group02' as slow.

As I haven't mentioned the size of each SAS disk, lets assume using 'Disk Group01' a 10TB RAID5 virtual disk (VD) is created and using 'Disk Group02' a 12TB RAID5 VD is created. You can configure hot spares for each disk group if you have additional disks. As I mentioned above, for OS installation we have created a 10GB RAID1 VD using 'Disk Group03'. After installation of the OS (Open-E DSS V7), it scans and shows 10TB and 12TB as available storage units. 

Now the next step is to create volume groups. Here we created two volume groups (VG00 and VG01) to differentiate fast and slow storage. 

• VG00 uses VD01
• VG01 uses VD02

Once volume groups are created, you can now carve out LUNs separately based on your requirements. For example, if you want a LUN that is going to be used as a datastore to store your virtual machines, then you can create it on VG00 (fast), or if you need it for storing some general purpose backup files, then you can create it on VG01 (slow). So depending on your requirement you can decide where to create your LUN.

Note: Here I classified RAID disk groups based on speed. You can divide it based on reads and writes. So that you can choose RAID10 disk group for write intensive operations and RAID5 disk group for reads. It can even be divided based on access type. That means a disk group exclusively for sequential file access (SQL logs) and another disk group for random access (SQL data, VM datastore etc). 

RAID configuration using PERC

PERC stands for PowerEdge Raid Controller. Here we have 3 physical disks present. We will be configuring 2 virtual disks (VD) of RAID 5 using these 3 physical disks.

VD00 - 100 GB

VD01 - 1.7 TB

Once the system starts press Ctrl+R to enter PERC configuration utility and follow the steps as shown below.

No configuration present and 3 disks available

Press F2 and create new VD

VD00 properties

Click OK

VD00 - 100 GB created

Press F2 and add new VD

VD01 properties

VD00 and VD01 created

 Now we have successfully created 2 VDs. Next step is to initialize both VDs.

Initialization of VD00

Start Init

Click OK

Initialization VD00 in progress

Similarly initialize the next VD too. Once its completed you can exit from the PERC utility and reboot the machine.

RAID controller

As RAID controller is responsible for the operations on RAID array drives, it is very important to have an enterprise class controller for enhanced performance, increased reliability and fault tolerance. Considering the business requirement and budget, you can choose a RAID controller. Here I will be explaining about DELL Power Edge RAID Controller (PERC). When choosing a controller, there are few critical hardware features that affect performance to keep in mind :

• Read policy
• Write policy
• Controller cache memory
• CacheCade
• Cut-through I/ O
• FastPath

PERC Series

PERC H810 - high performance RAID controller that can be connected to JBOD

PERC H710P - ideal for implementing hybrid server platforms based on SAS HDDs with high performance and enterprise class reliability

PERC H310 - entry-level RAID controller (no cache)

Reference :
Dell
Microsoft