Date: Thu, 28 Mar 2024 06:29:16 -0400 (EDT)
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RAID, or Redundant Array of Independent Disks, integrates multip=
le disks into a single array to achieve faster performance goals like bette=
r hardware failover and improved disk Input/Output performance. We=E2=
=80=99ve summarized the primary RAID levels below.
Use our RAID Calculator to see how much raw space will be presented to y=
our operating system (OS) as a storage device based on your desired RAID le=
vel. HostDime servers are fully cust=
omizable during the order process to add RAID levels to increase performanc=
e.
RAID Levels Explained
RAID 0
- Summary: RAID 0 stripes data at the block level across each of the disk=
s in the array. Because the data is striped across multiple disks, you will=
see improved read and write performance, especially for larger files. This=
is due to the ability of the array to simultaneously read or write a block=
to each of the disks in the array. As such, the performance will tend to s=
cale with the number of disks within the array. A RAID 0 can contain two or=
more disks, with the maximum number being limited based on the number of d=
isks supported by your RAID controller and available drive bays for your se=
rver. Because RAID 0 spreads storage blocks across all of the disks in the =
array, any disk failure will result in the entire array being lost. As such=
, the risk of data loss due to a drive fault will also scale with the numbe=
r of disks within the array. We do not recommend using a RAID 0 for product=
ion systems.
- Capacity: VD =3D (C * n) | VirtualDisk =3D ( Capacity of one disk * num=
ber of disks )
- I/O Performance: Greatly improved read and write performance
- Fault Tolerance: None, increased risk of failure that scales with numbe=
r of disks in the array
RAID 1
- Summary: RAID 1 mirrors data at the block level on two disks. Each time=
a data block is written to the storage subsystem, your RAID controller wil=
l write that same data block on both disks, providing fault tolerance shoul=
d one of the disks fail. Because of this, the I/O performance characteristi=
cs will have slightly lower write performance compared to a single disk, wh=
ile read performance will be nearly double that of a single disk. This is b=
ecause when the RAID controller needs to write data it has to do so on both=
disks, however, when it needs to read data it can simultaneously fetch two=
different reads from either disk since the data set on both disks is mirro=
red. Because the data is mirrored on both disks in the array, either one of=
the disks can fail, as log as one remains functional, without causing the =
array to fail. NOTE: While most hardware based RAID controllers typically o=
nly support two disks in a RAID 1 array, some controllers and software RAID=
systems may support more than two disks. In these cases, write performance=
will slightly degrade as the number of disks increase and the read perform=
ance will scale with the number of disks.
- Capacity: VD =3D (C * n) / n | VirtualDrive =3D ( Capacity of one disk =
* number of disks ) / number of disks
- I/O Performance: Slightly lower write performance with nearly double th=
e read performance
- Fault Tolerance: n / n
RAID 5
- Summary: RAID 5 stripes data at the block level across each of the disk=
s in the array, while also calculating parity data, which is distributed ac=
ross the disks in the array to add fault tolerance. With a RAID 5 array, th=
ere will be one parity set distributed across the array, which allows for a=
ny one disk in the array to fail without causing the array to fail. Because=
the distributed parity needs to contain parity information for one disks w=
orth of information, the raw space provided by the array will be the total =
capacity of all of the disks minus one disks worth of capacity. This is als=
o why a RAID 5 has a minimum requirement of three disks. The I/O performanc=
e for RAID 5 will offer improved read and write performance, however, write=
s will not scale as linearly as a RAID 0 due to the RAID controller needing=
to perform the parity calculation and also store the resulting parity data=
. NOTE: While some software RAID systems support RAID 5, we do not recommen=
d this in a production because all of the parity calculations will need to =
be done by your servers CPU rather than the dedicated specialized hardware =
controller that is designed to accelerate these types of calculations. As s=
uch, a software RAID 5 will see CPU load scale with disk I/O and can often =
cause overloads as disk writes increase.
- Capacity: VD =3D ( C * n ) - C | VirtualDrive =3D ( Capacity of one dis=
k * number of disks ) - Capacity of one disk
- I/O Performance: Improved read and write performance
- Fault Tolerance: n - 1
RAID 10
- Summary: RAID 10 is a nested array containing RAID 0 of RAID 1 sets; in=
other words it is a RAID array of multiple RAID arrays. As such, this RAID=
level combines some of the performance characteristics of both RAID 0 and =
RAID 1. The I/O performance will be improved for both read and writes, whic=
h will scale differently based on the number of disks in the array. The rea=
d performance will scale with the number of disks in the array, while the w=
rite performance will scale with the number of RAID 1 sets in the array. Fo=
r example, a RAID 10 with four disks will have two RAID 1 sets that are the=
n part of a RAID 0, therefore the read performance will be nearly four time=
s a single disk in the array, and write performance will be nearly twice th=
at of a single disk. This RAID level offers a great combination of performa=
nce and fault tolerance. Half of the disks in the array can fail without th=
e array failing. This is because one disk in each of the RAID 1 sets can fa=
il without that RAID set failing. Because of these characteristics, you wil=
l notice that the minimum number of disks required will be four and the tot=
al must be an even number of disks, such that increasing the number of disk=
s in the array is done in pairs of disks. While the number of disks require=
d compared to the raw useable capacity is lower, this RAID level offers the=
best overall combination of performance and fault tolerance. This is a gre=
at option for read heavy databases or mixed work loads.
- Capacity: VD =3D (C * n) / n | VirtualDrive =3D ( Capacity of one disk =
* number of disks ) / number of disks
- I/O Performance: Improved write performance with greatly improved read =
performance
- Fault Tolerance: n / 2
Even with these RAID options, any server is vulnerable to data l=
oss in the case of drive failure. We recommend keeping multiple backup=
sets including both locally and off-site. Check out our Disaster Recovery Solutions and our Remote Backup Service for serious data protection.
If you have any questions, don't hesitate to contact our support team=
a>, available around-the-clock.
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