Basic RAID1 questions

GnatGoSplat

Golden Member
Apr 5, 2001
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I had never considered RAID1 in the past, but after recent Seagate 1TB drive failure, I think it's a good idea for me to consider RAID1.

I have a few basic RAID questions that are kind of hard to find detailed answers on.
  • The RAID that comes on a motherboard, that's considered software RAID, correct?
  • Software RAID would be a RAID system handled by the drivers, so would therefore put a load on the CPU?
  • A system with a very weak CPU would be better off with hardware RAID, correct?
  • How much of a hit does the CPU take on a software RAID on a modern AMD or Intel chipset?
  • I have read that RAID1 with a proprietary NAS, if the NAS hardware fails but drives are still fine, you will still have difficulty recovering data from the drives. How about if the RAID hardware is a regular PC, for example, an Intel H61 chipset running Windows? If the computer fails, can I just take one of the mirrored drives and hook it up via eSATA to another PC and read the disks as normal? Or do I need to get another Intel chipset board and set it up with OS and RAID driver to read the disks?
  • Similar to the above, if I had a hardware RAID SATA card and the card dies, do I need to buy the same card in order to read my disks?
 
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mv2devnull

Golden Member
Apr 13, 2010
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* Yes (or called "fakeRAID")
* Yes
* Yes, but RAID1 and rAID0 don't do heavy calculations
* Doesn't this site have an article about it?

* Controller writes into the disks the info that they are part of RAID array. That is called metadata. Different controllers (including pure software RAID) do use different metadata formats, and write metadata to different sectors on the disk. Therefore, it usually requires compatible system to read.

RAID1 is however very simple: a disk contains a copy of data and unique metadata. At least Linux (recovery CD saves the day) can read the data ignoring the metadata (or guess format and behave as proper RAID1 fakeRAID). Not so sure about hardware disks. NAS is most likely pure software or fakeRAID.
 

corkyg

Elite Member | Peripherals
Super Moderator
Mar 4, 2000
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Been using hardware RAID1 for over4 years for data. Have upgraded the HDDs about 2 times. Harware RAID has its own controller and BIOS, and loads just after system boot but prior to Windows loading. I also kleep the RAID1 array backed up by monthly cloning to an external drive. Each mirrored HDD in the RAID1 array can be separated and used as a single drive without any restore or aleration. I have never used mobo RAID because one of the ports was broken. I also run eSATA off of the hardware card.

Metadata is part of NTFS. All my HDDs have metadata.