Lifeline
Lifeline Communiqué
Communiqué
Date: 09th Nov 2011
Tip of the Day:
Hardware Vs Software RAID
Feature
Software RAID Hardware RAID
Cost: High
Low
Software RAID is part of OS, so no need to spend extract money.
Complexity: Low
The software RAID works on partition level and it can sometime
Medium to high
increase complexity if you mix different partitions and hardware
RAID.
Write back caching (BBU): Yes
The software RAID cannot add a battery. Hardware RAID can
run in write-back mode if it has a BBU installed. With BBU
pending writes are not lost on a power failure.
No
Performance: High
With the software based RAID0 and RAID1 performance is
negligible. However, performance goes down when you use
Depend upon
parity-based arrays and/or several arrays at the same time. The
usage
performance of a software-based array is dependent on the server
CPU performance and current load.
Overheads (CPU, RAM etc): No
The software RAID must use server's CPU and RAM for RAID
Depend upon
software. The more hard drives means more CPU cycle will go to
usage
software RAID instead of your Apache / Postfix or MySQL
server.
Disk hot swapping: Yes
It means replacing hard disk without shutting down the server.
Many RAID controller supports disk hot swapping.
No
Regards, Team TSG, Infrastructure Availability
Services
Hot spare support: Yes
A hard disk is physically installed in the array which stays
inactive until an active drive fails, when the system automatically Yes
replaces the failed drive with the spare, rebuilding the array with
the spare hard disk included.
/boot partition: No Yes
It is hard to make fail over with software RAID if /boot fails
while booting the server. This can result into unexpected errors
and data loss. However, LILO and FreeBSD loader can get
around this problem too.
Open source factor: No
*BSD / OpenSolaris and Linux RAID software drivers are open
source. It means more people can fix problems as compare to a Yes
closed source hardware firmware. You can move, mix and match
different sizes with open source software RAID.
Vendor lock in (open formats): See above. No Yes
Higher write throughput: No Yes
Hardware RAID with BBU may offers higher write throughput.
Faster rebuilds: Yes
Hardware RAID with BBU may offers faster rebuilds as compare No
to software based solution.
Can act as a backup solution?: No No
Both software and hardware RAID cannot protect you against
human errors or system failures or viruses. Daily scheduled and
off site backups of your system are highly recommended. Use
tools such as rsync, rsnapshot, tar, dump, restore and others to
make daily backups.
Recommend usage: +Low cost +Do you run a
solution mission critical
+Better for cluster or setup?
RAID0 or +Heavy database
RAID1 driven dynamic
+Single server / site
workstation +Do you want the
+Perfect for highest
home and small performance
business users. possible?
+No vendor lock-
ins
Regards, Team TSG, Infrastructure Availability
Services
Lifeline Communiqué
Communiqué
Date: 09th Nov 2011
Tip of the Day:
Hardware Vs Software RAID
Feature
Software RAID Hardware RAID
Cost: High
Low
Software RAID is part of OS, so no need to spend extract money.
Complexity: Low
The software RAID works on partition level and it can sometime
Medium to high
increase complexity if you mix different partitions and hardware
RAID.
Write back caching (BBU): Yes
The software RAID cannot add a battery. Hardware RAID can
run in write-back mode if it has a BBU installed. With BBU
pending writes are not lost on a power failure.
No
Performance: High
With the software based RAID0 and RAID1 performance is
negligible. However, performance goes down when you use
Depend upon
parity-based arrays and/or several arrays at the same time. The
usage
performance of a software-based array is dependent on the server
CPU performance and current load.
Overheads (CPU, RAM etc): No
The software RAID must use server's CPU and RAM for RAID
Depend upon
software. The more hard drives means more CPU cycle will go to
usage
software RAID instead of your Apache / Postfix or MySQL
server.
Disk hot swapping: Yes
It means replacing hard disk without shutting down the server.
Many RAID controller supports disk hot swapping.
No
Regards, Team TSG, Infrastructure Availability
Services
Hot spare support: Yes
A hard disk is physically installed in the array which stays
inactive until an active drive fails, when the system automatically Yes
replaces the failed drive with the spare, rebuilding the array with
the spare hard disk included.
/boot partition: No Yes
It is hard to make fail over with software RAID if /boot fails
while booting the server. This can result into unexpected errors
and data loss. However, LILO and FreeBSD loader can get
around this problem too.
Open source factor: No
*BSD / OpenSolaris and Linux RAID software drivers are open
source. It means more people can fix problems as compare to a Yes
closed source hardware firmware. You can move, mix and match
different sizes with open source software RAID.
Vendor lock in (open formats): See above. No Yes
Higher write throughput: No Yes
Hardware RAID with BBU may offers higher write throughput.
Faster rebuilds: Yes
Hardware RAID with BBU may offers faster rebuilds as compare No
to software based solution.
Can act as a backup solution?: No No
Both software and hardware RAID cannot protect you against
human errors or system failures or viruses. Daily scheduled and
off site backups of your system are highly recommended. Use
tools such as rsync, rsnapshot, tar, dump, restore and others to
make daily backups.
Recommend usage: +Low cost +Do you run a
solution mission critical
+Better for cluster or setup?
RAID0 or +Heavy database
RAID1 driven dynamic
+Single server / site
workstation +Do you want the
+Perfect for highest
home and small performance
business users. possible?
+No vendor lock-
ins
Regards, Team TSG, Infrastructure Availability
Services
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