RAID Config

[Jackson Khoo]

My Q is very simple:
I have 6 physical harddisks on my server. If I configure all HDD (total 5)to be RAID 5 including system disk (WIN2K OS) and with 1 HDD to be hot standby, will my OS crash if 1 of the HDD crashes in future?

TQ

[S.K. Chan]

Put aside OS and if we're just talking RAID then if one of your RAID5 disk is dead, your other 4 RAID5 disks will still continue to run because of error correction striping even without the hot spare. With the hot spare in place, rebuild of your RAID5 bad disk will happen on this disk. So the answer to your question is no.
Side note .. why not setup RAID1 (100% redundancy) on 2 drives as your OS drives and the rest RAID5 (only need minimum 3 disks) as data disks ?

[Jackson Khoo]

you've answered portion of my answer, but still i concern on OS. as i have read an article from internet, raid 5 is not recommended for OS because OS system file is striping accross the raid 5 HDD, and when 1 of the HDD fails, some OSes might fail to run at all as raid 5 is not a clone/mirror.

[Jon Mattatall]

That's what he's suggesting.

Rather than use all 6 drives in a RAID-5 setup (or RAID 0+5/6), dedicate 2 drives to RAID-1 (mirroring) and use those for the OS. That still leaves you with 4 drives, more than enough for RAID-5, that you can use for data.

Jon

[Vincent Fleming]

Your OS will run even if a drive fails.

I don't understand how some people still question RAID technology - it's been out for *years*. Thousands and thousands of production systems boot from RAID every day.

RAID-5 or RAID-1 does not matter. They both protect against single drive failures.

RAID-1 with only 2 drives is only margianlly more reliable than RAID-5 with 5 drives. Reliability should not be your determining factor here - but performance may be. RAID-1 will perform slightly better if your system swaps heavily. If not, the RAID-5 should perform the same or better than RAID-1.

Good luck!