Server Tech

Expand your Server Storage with JBOD – Just a Bunch Of Disks

JBOD (Just a Bunch Of Disks) is the most cost effective way to increase the Direct Attached Storage (DAS) capacities on servers. In this article, we will see what is JBOD and how you could expand your server storage with JBOD quickly and easily. We will also have a look at the chassis based enterprise level JBOD’s that are available.

What is a JBOD?

As the acronym goes, JBOD stands for Just a Bunch Of Disks. If you have, say three disks in your server you could use JBOD to combine all the three disks and make it appear as a single larger disk to applications. JBOD is also used to refer to external chassis based drive arrays that connect to the RAID controller/ HBA’s in the server to expand the total storage space available with the server (DAS). But here, expansion happens outside the server. Sometimes, all the storage is kept outside the server in order to make more room for other components in the server. In JBOD, the data is stored in the first disk, and when that is full, its stored in the second disk, and so on… JBOD’s work with SAS / RAID Controllers (or) HBA’s within the servers and connect to them using SAS/SATA interfaces among others.

What are the advantages of JBOD?

  • A JBOD utilizes the entire disk capacity for storage. So, if there are three disks with x capacity, 3x disk capacity can be obtained with JBOD, unlike RAID where some storage space is always lost to provide redundancy.
  • JBOD is the most inexpensive method of increasing the storage capacity in servers.
  • JBOD enables to expand the storage capacity with disks placed outside the server. This is still a Direct Attach Storage architecture, but only the disks are outside the server. This provides for a huge expansion of storage capacities.
  • JBOD provides more space inside the server to accommodate more processors etc, if all (or much of) the disk drives are connected externally.

What are the dis-advantages of JBOD?

  • Generally, if one disk of the JBOD array is lost, then the data in all the disks are lost. So, its important to back up data frequently when using JBOD configurations.
  • There is no increase in Read/Write speeds with JBOD.

A note on the Chassis based Enterprise class JBOD’s:

Enterprise class JBOD’s sometimes come in modular/ rack-mountable chassis based enclosures where the individual 2.5″/3.5″ drives can be inserted. So, this is essentially an external DAS solution connecting to the SAS controller/ HBA in the server through SATA/SAS connectivity (mostly). Each chassis unit can accommodate 12/24 drives, based on the model/vendor. Some vendors allow interconnection of multiple such chassis based JBOD units to increase the storage capacity even further.

These JBOD arrays have specialized redundancy options for components like cooling fans, power supplies, etc. Some of them even have vibration isolation for multiple disks placed close by. Some of them even provide hot swappable disk drives for higher reliability.

So, if you think creating a separate Storage Area Network might be too expensive, the enterprise chassis based JBOD’s might just be for you!

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