Raid 0 + 1 What are the benefits, how do they work

  Major Disaster 10:32 03 Dec 2005


I am just thinking about RAID.

I know that with RAID 0, data is split equally between the two identical drives and so provides a performance increase. But i am wondering how this works. Say i save a file, do they two drives appear in my computer as one (say C:\) and i save it there and then is is split over the two physical drives or do i have to save the file twice or what? Also in the case of one drive failing what would happen? And where is the OS installed? On both or one or what?

Now RAID 1, data is mirrored and saved twice. Is this much slower process? Where is the OS installed? Again, Say i save a file, do they two drives appear in my computer as one (say C:\) and i save it there and then is is copied over the two physical drives or do i have to save the file twice or what? Is this the perfect backup by having two complete versions of everything?

Thanks for any help, soo many questions i know

  PaulB2005 10:41 03 Dec 2005

With RAID the RAID drivers control where the files are sored and how.

RAID 0 - You have one drive with the total capacity of twice the smaller of the two drives. ie 20 Gb + 40 Gb drive = 40Gb drive, 80Gb + 80Gb = 160 Gb drive. The two drive act as one drive. If one drive fails you loose everything. Hence RAID 0 isn't really a RAID at all. RAID = Redundant Array of Inexpensive Drives. In RAID 0 there is no redundant drive.

RAID 1 is slower on writes as everything needs to be written twice but is faster on Reads as it can Read simultaneously from both drives. But you have the redundancy that means if one drive fails you still have a copy. You still only see one drive.

  PaulB2005 10:45 03 Dec 2005

click here

Ignore some of my ramblings....

  Major Disaster 10:47 03 Dec 2005

Thanks for the help.

So RAID 1 is looking like a winner. But is an OS installed on both drives? So both drives are COMPLETELY the same?

Thanks again PaulB2005

  PaulB2005 11:01 03 Dec 2005

It's not really installed on both but installed on one and mirrored (copied) on the other. It's like an "on the fly" backup.

Once you have set up the RAID array (usually in the BIOS) the 2 disks will be seen as one and the OS will install as if it was just one ordinary disk.

  PaulB2005 11:04 03 Dec 2005

Also note the capacities are different.

With RAID 0 you get one big disk at twice the capacity of the smallest disk - 60 Gb + 60 Gb makes one big 120 Gb disk.

But with RAID 1 you only get one 60 Gb disk but the data is stored twice for protection.

  Longhouse 11:14 03 Dec 2005

If you have valuable data to protect - go for RAID 1 (mirrored array).

I set up with 1 x c: drive for OS (which in my case is PATA IDE) and SATA RAID as data store and it's just saved my bacon BIG style when a RAID drive failed! Well worth the "extra" cost of a drive.

  Major Disaster 00:06 04 Dec 2005

If i am just a normal home user (games, music, word processing, internet etc.) is raid really necessary for me of would a SATA surfice?

Thanks again

  PaulB2005 00:13 04 Dec 2005

I would (and do) stick to normal SATA.

I keep toying with the idea of switching it to RAID 1 but haven't had the bottle yet. I currently have two 80 Gb drives with one as the main and the other partitioned up for archiving and backups. Also not sure how Acronis True Image 8 will handle RAID drives.

However i have an old PC with 2 hard drives which i could experiment with but have no RAID controller. click here is £16 but not good reviews. Good RAID Cards seem to be expensive.

So not necessary but maybe an idea if you want to try.

  Longhouse 00:19 04 Dec 2005

Difficult for me to need to decide if your data (word docs, music, etc) is valuable, and how much you keep, ease & frequency of access required.

If only smallish amounts of data, then you could just back up to CD-R or CD-RW. In my case, I have over 30Gb of data stored and archived (some of it from contracts > 5 years ago) and I refer to it regularly.

SATA or EIDE are fine for every day use - but I still prefer to have a second drive installed where I run the windows swap file and keep data separate from OS.


  Chegs ®™ 01:48 04 Dec 2005

As a homeuser I would steer clear of RAID 1(mirrored)especially if your using SATA as I tried it with my Gigabyte mobo and 2x120Gb SATA's.One of the drives was(still is)a lazy so-and-so,meaning on cold boots one SATA was always causing an "Incomplete RAID set.Press F4 to enter RAID utility" message,which on entering only offered the choice of deleting RAID set and recreating it,then reinstall all OS + apps.After doing this daily for several weeks,I finally left the PC on 24/7(still do)but the the SATA drives failed.I was given new HD's from Maxtor,and setup the OS on an IDE(15Gb)partitioned in two equal sized chunks(7.5Gb)to carry the OS and setup the SATA's as partitioned into 4 chunks each,creating vast storage where I save downloads,video files,images of the IDE HD,etc.

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