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RAID 1 vs Backup Software breakdown?

L

limitedaccess

Supreme [H]ardness
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May 10, 2010
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I'm wondering what the pros/cons of using RAID 1 vs Backup Software and a second drive of identical capacity?

The hard drives would either be a Hitatchi 5k2000 2TB or WD Caviar Green 2TB. Using the P67's on board RAID versus a free (or low cost) back up software. As you can see ideally I'd like to spend as low as possible. Nothing is really "mission critical" or irreplaceable, it is really more of a convenience issue should hardware failure occur or errors.
 
RAID 1 is not a backup. Even if you have RAID 1 you still need to backup. RAID 1 prevents data loss due to a single drive going bad nothing more. It does not protect against a virus, accidental deletion, power supply death killing all internal disks at once ...
 
RAID 1
PROS: It gives instant duplication, can provided increased read performance, no down time when a drive fails.
CONS: All mirrored drives ran at once(more power consumption and wear on drives), it's possible that the cause of a drive fail could also damage the mirrored drives(fire in/near case, electrical power surge/short, virus), doesn't protect against accidental file deletion.
 
As previously posted, RAID1 performs a different function than backup.

One is for continuity in case of failure, the other is for recovery in case of disaster.
 
lovemyram4x4 said:
RAID 1
PROS: It gives instant duplication, can provided increased read performance, no down time when a drive fails.
Click to expand...

Increased read speeds will only happen if FakeRAID or hardware RAID is used, not software RAID.
 
On linux you can get increased read speed with software raid 1. On windows this will not happen with the OS raid.
 
drescherjm said:
On linux you can get increased read speed with software raid 1. On windows this will not happen with the OS raid.
Click to expand...

No, it doesn't have any increased read speed, in either OS.

The only reason FakeRAID or hardware RAID can get increased read speed is due to the controller being able utilize all disks at different moments, software RAID is controlled at the OS level and thus the disks must read/write at the same time, so no increased speed.


Also, there is no such thing as OS RAID. Windows has a built-in RAID tool and management system, Linux distros have MDADM. They are both controlled at the OS level.
 
Red Falcon said:
No, it doesn't have any increased read speed, in either OS.

The only reason FakeRAID or hardware RAID can get increased read speed is due to the controller being able utilize all disks at different moments, software RAID is controlled at the OS level and thus the disks must read/write at the same time, so no increased speed.
Click to expand...

it always depends on the quality of the Raid implementation.

If your driver/ controller/ os is intelligent enough to read from both disks independantly, you will see a increase in reads especially in random reads.

The same with data security
While you will always need a backup for disaster recovery ex. due to a fire or a failure of the power supply or a buggy OS or driver, there are options to prevent data loss on mirrors mostly.

Ex if you use a ZFS software mirror, you have increased speed, you can handle accidentally deleted files or virus infected files with snapshots or silent data failures or damaged blocks on one of the mirrors with the help of end to end checksums to detect errors and online scrubbing to repair them.

You do not have any of these features with most other mirrors.

Gea
 
Red Falcon said:
No, it doesn't have any increased read speed, in either OS.

The only reason FakeRAID or hardware RAID can get increased read speed is due to the controller being able utilize all disks at different moments, software RAID is controlled at the OS level and thus the disks must read/write at the same time, so no increased speed.
Click to expand...

This makes absolutely no sense, and demonstrates a fundamental lack of understanding of RAID and disk IO in general.

drescherjm's statement was correct, linux mdadm RAID 1 can get increased read speed over that of a single drive, in some cases.
 
Red Falcon said:
The only reason FakeRAID or hardware RAID can get increased read speed is due to the controller being able utilize all disks at different moments, software RAID is controlled at the OS level and thus the disks must read/write at the same time, so no increased speed.
Click to expand...

ZFS Raid-1 vdev's (mirrors) will stripe reads off disk.
 
john4200 said:
This makes absolutely no sense, and demonstrates a fundamental lack of understanding of RAID and disk IO in general.

drescherjm's statement was correct, linux mdadm RAID 1 can get increased read speed over that of a single drive, in some cases.
Click to expand...

No, his statement is incorrect and you are the one showing a lack of understanding of RAID and disk I/O in general. :rolleyes:

I get that ZFS can, but how can MDADM?

I use RAID 1 with MDADM and get no read speed performance increase.

wtf are you talking about?

With my two 1TB green drives, I should be able to get 160MB/s+ with read speeds if there was a boost. I see ZERO increase in read speed and my speeds stay at around 110MB/s, the same speeds as when a single drive is used.

However, those same two drives on a FakeRAID controller, I do see the speed performance increase to said speeds.

Show me some proof.

Until I see some, you're blowing steam out your ass.
 
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_Gea said:
it always depends on the quality of the Raid implementation.

If your driver/ controller/ os is intelligent enough to read from both disks independantly, you will see a increase in reads especially in random reads.
Click to expand...

Yeah, if a Solaris OS is used with ZFS, I get that, but it's not exactly software RAID now is it since it also includes a file system.

MDADM can't do that.

Also, I know the driver/controller can get the read-speed increase, that's because it's FakeRAID.

It has nothing to do with the "quality" of the RAID setup, it has to do with the type and the hardware being used.

When we say software RAID, we mean either WIndows RAID or MDADM Linux RAID. We aren't talking about ZFS since it is technically RAID+FS.
 
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It is a waste of my time to try to educate the arrogantly ignorant. Suffice it to say the drescherjm's statement is correct, and that you really should do some research and learning before continuing to make such ridiculous comments.
 
john4200 said:
It is a waste of my time to try to educate the arrogantly ignorant. Suffice it to say the drescherjm's statement is correct, and that you really should do some research and learning before continuing to make such ridiculous comments.
Click to expand...

If it's a waste of your time, then why post?
 
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This is as far as I can tell because mdadm is not set up to do load balancing - has nothing per-se to do with software vs fake raid. The freebsd geom mirror code can easily do this, as does zfs (and it has nothing to do with being filesystem vs a volume/mirror manager.)
 
danswartz said:
This is as far as I can tell because mdadm is not set up to do load balancing - has nothing per-se to do with software vs fake raid. The freebsd geom mirror code can easily do this, as does zfs (and it has nothing to do with being filesystem vs a volume/mirror manager.)
Click to expand...

How does one go about setting up load balancing on software RAID?

I'll checkout the freebsd version as well.

Thanks for the info, I'll look more into it.
 
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danswartz, thanks for showing me that.

Apparently the "load" algrorithm will allow this version of software RAID to have up to a 50% read speed increase, which is similar to what I see using FakeRAID controllers with two disk drives.

There are other algorithms, but it seems that each has a specific purpose.

To my knowledge though, there is no way to change this in MDADM or Windows RAID.
 
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Kind of a bummer linux doesn't do this. This is one reason I like zfs - it combines a raid system, volume manager and FS all in one.
 
danswartz said:
Kind of a bummer linux doesn't do this. This is one reason I like zfs - it combines a raid system, volume manager and FS all in one.
Click to expand...

Yeah, I have to agree. I might be switching up my sever setup sooner than I thought. ZFS is very nice.
 
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