#3par copy space series

Virtual volumes (VV’s) draw their space from CPG’s and in the case of thin provisioned VV’s grow on demand and only consume space from the CPG as needed. Whilst CPGs have many unique features for simplicity in traditional terminology you can think of a CPG as a RAID group.įinally we get to the building block we are able to assign to a host, Virtual Volumes.

#3par copy space series

We will cover CPG’s in part 2 of this series in detail, but for now just know CPG’s are a pool of space. CPG’s are simply a number of logical disks joined together to form a contiguous space. The next logical layer down is CPG’s ( Common Provisioning Groups). A logical disk is a collection of chunklets arranged as rows of a RAID set. The number of RAID sets combined together is the row size, for example if the above orange and blue RAID 1 sets are combined together the row size would be 2. To allow for large volumes of data and to enable the data to be striped across as many disks as possible, multiple RAID sets are combined together in rows. The orange and blue chunklets are members of a RAID 1 1+1 set co-existing alongside a RAID 5 2+1 (Green) set and a RAID 5 3+1 (yellow), all on the same physical disks. The diagram show 4 physical disks with different coloured chunklets representing membership of different RAID sets. Looking at the diagram below we see chunklets enable not only multiple different RAID sets to exist on a single physical disk but that they can also have different RAID levels. To summarise in a traditional storage system each disk is dedicated to being a member of one RAID set, by using chunklets multiple RAID sets can co-exist on the same set of physical disks. a 450 GB disk would consist of 450 chunklets. For example there is a yellow RAID set made up of a data chunklet from the first 2 disks and a parity chunklet from the 3rd disk, real world there would be a lot more chunklets per disk i.e. In this simple example above we see 3 physical disks each with 4 chunklets per disk, each different colour represents membership of a different RAID 2+1 set. Let’s zoom in on a small number of disks to see how this looks. In a 3PAR system like in a traditional storage system RAID is used to combine multiple disks together but instead of using entire disks data is striped across chunklets. Prior to the 7000 and 10,000 series the chunklet size was 256MB, the reason for the increase to 1GB was to reflect the growing size of disks. This is what happens in a 3PAR system, whenever a disk is added to the system it is divided into 1GB blocks of space called Chunklets. Over time Chunklet mellowed out, he realised hey it’s good to share and instead of demanding a whole disk to himself he was happy with 1GB of any given disk. This traditional and inflexible approach is shown in the diagram below:

So on a traditional storage array to set up a simple RAID 5 2+1 set, you would need 3 disks, 2 data and 1 parity each of which was dedicated entirely to being part of that RAID set. He existed on a traditional storage array and since he didn’t get on with anyone he demanded a whole disk to himself. Things were not always so good for Chunklet, back in the day Chunklet was a bad dude with a bad attitude. Let’s introduce Chunklet, as its Chunklet that enables 3PAR to have a unique architecture and enable many of its capabilities. The perfect place to start is by looking at the 3PAR architecture, and specifically how 3PAR uses layers of abstraction to deliver a unique and flexible approach to RAID. I wanted to start a series of posts looking at 3PAR 101, a back to basics/ beginners guide to 3PAR.