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Setting up RAID 5 using Compaq Smart Start

awiggins (MIS) (OP)
16 Feb 01 14:28
I have 5 x 18.2gb hot swappable disks which I want to set up as Raid 5.  I chose the Raid 5 option in smart start and it listed the 5 disks.  When I look at the logical drive - there is only one.  Is this right ?  I would be grateful if anyone could tell me how to set up raid 5 properly.

Cheers
Guest (visitor)
16 Feb 01 16:06
If you set it up to be a RAID 5 array you will see it as 1 logical drive.  The drive will be appx 68 gig with the remainder of the disk space for parity.  Smart Start gives you the option to set it up however you like, and will tell you how much disk space will be  available. Just place an X on the type of RAID you would like. After your RAID controller initialises it will say 1 logical drive detected or something like that.  I'm running NT, when I go into Disk Admin it shows as if there is no RAID or fault tolerance because the RAID controller handles it. To NT it's just 1 disk.  I hope this answers your question.

Alex
pauldune (IS/IT--Management)
22 Feb 01 9:49
Hello,

The logical drive is a virtual drive wich consists of the 5
drives together.The 'combining'of the drives is done in the hardware of the raidcontroller, and the raidcontroller reports to the operating system only the logical drive.  
So this is normal.
You could consider using a hot spare. Then you use only 4 drives for the array, and the last one as an automatic backup drive. if one of the drives fails, the backupdrive automaticaly takes over. Then you can order in all peace and quiet a new drive.Remember that with raid 5 arrays, you lose a certain amount of disk space for your extra security
(redundancy).With an array of 5 disks this is 1/5, with 4 disks, 1/4.

gtx
Paul
bedardpa37 (IS/IT--Management)
12 Jun 01 22:53
I can only suggest that you do not create one logical drive. This in the future will haunt you, beleive me, it will.  I can only suggest that if you plan your directory structure in advance, you would have more than one logical drive.  Don't go with one, plan it out, think it through, and then do what make sense.  
I will let you think it through, and then, if you still can't figure it out, let me know !  But there are better ways to manage hardware level RAIDS.....
dieselfreak (TechnicalUser)
23 Jul 01 8:36
Also worth noting that for performance you should split the OS onto its own logical disk preferably a mirror set, as they offer higher performance than a raid 5 set.
vb8304 (IS/IT--Management)
25 Jul 01 12:32
What about using RAID 0+1 instead of RAID 5 since you get better performance and Faul Tolerance. I am about to use this for our exchange server with 10 36.4 GB drives in a Disk Array with 2 9.1GB mirrored for the OS. My only problem is I am not sure, on WIN2K, hot to setup RAID 0+1. Can this also be done through the Smart Start?
Thanks.
Vince.
dkediger (MIS)
25 Jul 01 13:45
vb8304:

RAID 5 provides fault tolerance equal to RAID 0+1 with fewer disks, and with an adequate controller, you won't notice the write performance.  Since we're in the Compaq forum, their 4200 controller is designed to do this with 64MB of cache - they may have newer controllers that do the same.  I'm not sure, but does 0+1 support hot swapping - I would think you would have to break the mirror set first, swap the disk, and rebuild the mirror.

It really comes down to a question of evaluating costs of more disks versus costs of a more advanced controller.
dieselfreak (TechnicalUser)
27 Jul 01 15:33
RAID 0+1 does support hot swapping.

RAID 0+1 can be setup using smartstart, just select a custom configuration when configuring the array controller, RAID 0+1 is one of the options listed.
Guest (visitor)
10 Aug 01 5:10
What if OS fail , data which are on RAID 5 still remain or not ?
I plan to setup    RAID 5 for Data  and RAID1 for OS  with COMPAQ ML370  . But if my OS  fail  does it help by this method ?  and the performance of  writing  data to server   will  be decreased or not ?

My system is like below
-------------------------------------------------------------------------------
 O<-->O(2HD Mirror)  |  OOOO( RAID5) +  O(Spair online HD)
         OS   W2kADV                         SQL DATABASE               
--------------------------------------------------------------------------------

Thanks for ur recommendation in advance
dieselfreak (TechnicalUser)
10 Aug 01 5:41
a recomended configuration for a SQL server would be;

OS > mirrorset
SQL logs > mirrorset
SQL Database > Raid5

This would be a typical configuration of a SQL server, although if your logs are very large you may have to use a Raid5 set for them..
e.g
2 x 9.1Gb in a mirrorset gives you 9.1Gb of space if your Logs are going to require more space, then you may have to use Raid5 (and more than 2 disks) with the 9.1Gb disks to create a logical disk large enough.

Spliting the Data logs and OS up is really a performance thing, If the OS is dead so is SQL, but in answer to the question, yes the data will be still on the RAID5 set if youy lose the OS.
BertMan (IS/IT--Management)
12 Nov 01 12:05
Recommended config for SQL:


OS - Raid 1 (mirror)
SQL - RAID 10 with an online spare
T-logs - RAID 1 (mirror)

Also, if feasible, put the OS paging file on it own stripe set...

This solution would give you the utmost performance and redundancy for a SQL box...
Guest (visitor)
27 Feb 02 7:09


   system ml370 raid5 os winnt4

      problem Hd Fdisked, booting from nt4 cdrom "cannot find oemsystem.inf file"

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