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Software Raid 5 question

B

BoKingWen

Senior member
I am planning to setup a software Raid 5 on my Dell SC400 running Window Server 2003 but not sure if my setup will work since I don't have 4 identical drive I only have 2 pair of HD. I read from the web that for software raid you do not need to have 4 identical drive.

my setup:
2 x 300 IDE HD
2 x 150 SATA HD

Is this raid setup possible? will I be able to get 900G space or I need to use 1 drive for spare?
 
Originally posted by: BoKingWen
I am planning to setup a software Raid 5 on my Dell SC400 running Window Server 2003 but not sure if my setup will work since I don't have 4 identical drive I only have 2 pair of HD. I read from the web that for software raid you do not need to have 4 identical drive.

my setup:
2 x 300 IDE HD
2 x 150 SATA HD

Is this raid setup possible? will I be able to get 900G space or I need to use 1 drive for spare?
Click to expand...

Raid considers all drives the size of the weakest link.

So you will essentially have 4 drives in a RAID 5 at 150GB per drive. This mean 450GB of information total with 150GB parity.

One note, software raid 5 is excessively slow, slower than a single drive by a good amount in fact.

Your best bet in this case is a Raid 1 for the IDE and for the SATA drives seperately. This still gives you 450GB total, but none of it is wasted now, and reads will be faster. Plus a failure of a single drive will not affect the other 3, simply its counterpart.
 
One note, software raid 5 is excessively slow, slower than a single drive by a good amount in fact.
Click to expand...

Depends on the implementation and whether you have CPU/RAM bandwidth to burn. Modern Windows/Linux RAID5 can perform quite well -- albeit at a decent CPU power and RAM bandwidth cost for writes. If your server has CPU power to spare, it generally works fine. If you are running CPU-limited applications, it will not.

Your best bet in this case is a Raid 1 for the IDE and for the SATA drives seperately. This still gives you 450GB total, but none of it is wasted now, and reads will be faster.
Click to expand...

Sustained reads will be noticeably slower, since RAID1 is not striped (write performance may be a wash, though RAID5 will still probably be better). Doing a RAID10 (a RAID0 of two RAID1s) would make some of this up, though you might not be able to do that with mismatched arrays like this (you might be limited to 300GB total).

Please don't offer advice if you don't know what you are talking about...
 
Yes I have a lot of CPU power for the raid that is one of the reason I am thinking of going for the software raid in window 2003 server. From the articles i read from the web the CPU usage is not that much for a software raid. I guess I will pass for raid setup since I won't be able to use at least 70% of the total storage.

Thanks for the quick reply.
 
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