RAID performance question?

[cpjust]

Hi,
I'm not an IT guy, I'm just a developer, so my knowledge of RAID is pretty limited.

I was thinking of setting up 2 SATA 3.0 Gbps drives in a RAID 1 on my home PC (Win XP Home). I originally wanted to try RAID 5 or 10, but scaled back for now.

I've seen sites that give you general speed descriptions like Low, Med, High... but I'd like a little more specific answer. As I understand (or imagine?), if I have 2 drives in a RAID 1, the Write performance should be the same as a single drive (since it has to write the same thing to both drives); but as for Read performance, it should be double the performance of a single drive since it can read two different files (1 on each drive) at the same time? Is that a correct assumption or does a RAID 1 have to read the same thing from both drives to verify neither drive has become corrupt?

I know a RAID 0 is best for performance, but I want security also, since I'm not a big fan of doing backups...

 

[wahnula]

cpjust

Here is a great guide to RAID levels and their basic concepts, features and read/write speed comparisons.:

http://www.pcguide.com/ref/hdd/perf/raid/levels/multLevel15-c.html

Yes, RAID 1 offers faster seek times and is quite resilient. I bad a RAID 5 go down and turned it into RAID 1 (redundancy does not take the place of backups) and the overall speed increased. Here's a no-brainer that I learned the hard way: If your RAID 1 array degrades, do not try and rebuild with the orphaned drive. Replace it.

I thought it was just a glitch, they lost lock-step for just a split-second, (server still worked fine with one drive, got one last backup before this boneheaded event) and tried to rebuild with the old drive. Bad idea. Old drive took the good one with it upon rebuild. The story had a happy ending as I had run a full backup immediately prior and was back up in a few hours (always have spare drives around!) but it was a valuable lesson learned.

Tony

 

[technome]

With one of the most common raid adapter manufacturers, Lsilogic, simple raid 1 does not read from both drives, if you setup a raid 1, it reads from 1 drive of the set; I setup many raids since 1990, and this is always the case. If you go raid 10, then it reads from more than one drive.
Raid 5, overall, easily out performs raid1, as the reads are very much faster, the writes have a penalty due to parity creation, but unless a server is highly utilized this has minimal effect due to caching; the other factor, on average, a server or machine does about 80% reads/20%writes.The best raid is raid 10, very high read and writes.
Other factors which affect raid performence..cpu utilzation, software or device based implementation, driver programming quaility, coprocessor/onboard electronics speed, drive firmware, raid adapter firmware.


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Chernobyl disaster..a must see pictorial

http://www.kiddofspeed.com/default.htm