accessible as independent hard disk drives. ... JBODs as individual hard drives ... redundancy and read/write performanc
White paper
JBOD WHAT ? WHY ? FOR WHO ?
JBOD or “Just a Bunch of Disks” is an architecture combining multiple drives together to either, form a single or a group of logical volumes—also called “spanning”—or make them accessible as independent hard disk drives.
A JBOD’s primary advantage is to be able to use the entire capacity of every disk in it, for storage. For example, a JBOD made of three
disk fails, there’s a high chance to lose the
disks, with three different capacities with a
whole array. Rebuilding the array is however
total of 900GB, will provide 900GB of usable
possible but slowly. Another risk of JBOD is
capacity.
that, because the data stream is stored on
one disk at a time, it can affect the overall
A RAID array made out of the same
performance of a system.
drives will offer less than 900GB of storage capacity because of the need to store
mirrored dat or parity information. How
of an infrastructure (Host, Cloud, SDDC, etc.)
much capacity is lost to achieve the desired
typically is the storage sub system. Whatever
balance
availability,
the type of storage systems (SAN, NAS,
performance, and capacity depends on the
etc.) you are looking at a significant CAPEX
RAID level.
investment.
between
reliability,
The main risk with a JBOD array is
that it offers no redundancy at all. If a single
Nowadays the most expensive part
The most recurrent questions when considering a JBOD storage system
How to reduce costs and, at the same time, generate more space without using to many resources?
How to improve the usefulness of a JBOD when upgrading a cluster?
How to scale up the storage capacity while mitigating the risk of drive failure?
The unobvious answer is: use JBODs as individual hard drives and handle them independently in a RAID array
This architecture, also called Direct-
There are a few subjects of concern
will improve the
to consider when choosing a JBOD among
space in server computers by reducing
which: the number of expanders (single or
the amount of disks used in order to make
redundant), the type of connectivity, SAS or
more room for other components. It will also
SATA drives, cables, bus lanes, HBA vs RAID
reduce cost and time by freeing oneself from
cards.
attached storage (DAS),
the painful question of “what configuration do I need?” when upgrading storage capacity.
To achieve superior performance,
a JBOD unit requires drives of a high build quality and reliability as well as outstanding connectivity. Over the past years, the need for increased bandwidth and flexibility in storage systems made the SCSI and SATA standards an inefficient option.
To achieve best performance and reliability, the following three components are key when choosing and configuring a JBOD.
1. Connectivity
Passing large data through a small cable can be challenging, especially when trying to
achieve high read/write performance. The table below summarizes the compromises of each connectivity type often found on JBOD systems:
Performance
Cost
Distance
Fibre Channel
High
High
Long
GbE iSCSI
Low
Low
Long
10 GbE iSCSI
High
High
Long
SAS2 6Gb/s (SFF-8088)
Low
Low
Short
SAS3 12Gb/s (SFF-8644)
High
Low
Short
Very High
Medium
Long
QSFP+ (up to 48Gb/s)
2. Expanders
The SAS expander is a chip installed on the chassis backplane that function like a
switch, multiplying the number supported drives. JBODs with two expanders will increase redundancy and read/write performance by load-balancing the data stream on two links instead of one (more bandwidth) and thus reducing the bottleneck.
3. Drives
Due to their high number of drives,
The chart below was published on Q3
JBODs are often made of mechanical drives.
2015 by Backblaze, a major player in low cost
These are a key component of the storage
cloud backup and storage services. It shows
unit. Expect them to fail every now and then
their experience with hard drive failures over
or to add new ones to expand the capacity of
2013, 2014 and 2015 on a manufacturer basis.
the JBOD. While considering the speed and
Please be aware that the capacity of their
capacity of a drive, it is very important not to
drives and how they used them, most likely
overlook its reliability.
differs from your own setup and systems.
2CRSI, designer and manufacturer of server computer solutions offers a high-density, high capacity (up to 600TB), scalable and cost effective JBOD solution, the ULYS 460-J.
It can fit up to 60 Ultrastar® 3.5-
The enclosure can fit up to sixty HGST
inch hard disk drives in a 4U enclosure and
10TB Helium Ultrastar® hard disk drives to
comes with a dual 2-link SAS 12Gb/s (4)
achieve a maximum capacity of 600TB. That’s
QSFP+ connectors for higher redundancy
a massive half Peta Byte of storage! HGST
and performance. The (4) QSFP+ connectors
hard disk drives delivers today’s highest
provide up to 48Gb/s of data transfer speed.
capacity, performance for business critical applications and reliability ratings, with an
ULYS 460-J has two 1650W hot-swap
MTBF (mean time between failures) of up
redundant power supplies with one huge fan
to 2.5 million hours and a low 0.35% AFR
for cooling (that’s the only two fans in the
(Annualized failure rate).
system, so it’s quiet), an RS 232 serial port and three LEDs to communicate the status of the system. The chassis has been designed in such a way as to prevent it from bending under the weight of the disks.
ULYS 460-JBOD: connection type and read/write performance
Single link from the controller to the JBOD expander (over a QSFP+ SAS3 12Gb/s
cable from (1) x8 PCIe HBA/RAID card to (1) JBOD expander): This configuration offers no redundancy and a typical read/write performance at approx. 4500 MiB/s MAX, (1M sequential R&W Ramp Worker Balanced).
Throughput (in MiB/s) on the 60 hard drives Ultrastar He8 – using 1 link connection
ULYS 460-JBOD: connection type and read/write performance
Dual links from the controller to the (2) JBOD expanders (over (2) QSFP+ SAS3 12Gb/s
cables from (1) x8 PCIe HBA/RAID card to (2) JBOD expander): This configuration offers redundancy on the JBOD expander and a better read/write performance at approx. 6000 MiB/s MAX (+33% compared to single link), (1M sequential R&W Ramp Worker Balanced).
Throughput (in MiB/s) on the 60 hard drives Ultrastar He8 – using 2 link connections 1 HBA
ULYS 460-JBOD: connection type and read/write performance
Dual links from the controller to the (2) JBOD expanders (over (2) QSFP+ SAS3 12Gb/s
cables from (2) x8 PCIe HBA/RAID card to (2) JBOD expander): This configuration offers the highest redundancy and read/write performance at approx. 8500 MiB/s MAX (+89% compared to single link), (1M sequential R&W Ramp Worker Balanced).
Throughput (in MiB/s) on the 60 hard drives Ultrastar He8 – using 2 link connections 2 HBA (green line)
JBOD used as a DAS is one of the best and easiest solution to increase the storage of a datacenter in a cost-effective way and not thinking too much at what kind of product is needed.
2crsi.com North America +1 (925) 428-7910 http://2crsi.com
France/Europe +33 (0)3 68 41 10 60 http://2crsi.fr
Middle East +971 50 52 56 093 http://2crsi.com
