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RAID question

jdff
jdff asked
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Last Modified: 2010-04-19
I'm setting up a proliant server as the configuration follows:

Primary scsi drive 1st controller 36gb - windows 2003
Primary scsi drive 2nd controller 76GB - DATA Mirrored - RAID1
Secondary scsi drive 2nd controller 76GB - DATA Mirrored - RAID1

Now is that a bad setup? Is there a way to turn the raid 1 drives to become dynamic, I did not see that option on the disk manager.

Thanks
jdff
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Commented:
If I would do raid5 I would not have redundancy, is that right?

jdff
Commented:
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Author

Commented:
well if I don't make the 76GB RAID1 I will have no redundancy right? the 76gb is the DATA hard disk so I think I have to give priority to the data, don't you think? setting up as RAID5 will give me the ability of expanding later on but no safety on the data when comes to hard disk failure, Am'I correct?

Isn't dynamic partitions faster than basic?

Ok, now let's try a different question, what would be a good setup in order to read/write files of the server through the network?

Thanks, I would appreciate advices and experiences.
jdff
Fatal_ExceptionSystems Engineer
Top Expert 2005

Commented:
RAID 5 by definition provides the best redundancy you can have..  It just adds a parity stripe so when a drive fails, it can be swapped out and regenerated on the fly..  Definitely consider the higher RAID configuration..  The ONLY drawback to 5 is that you loose one disk to the parity stripe (worth of space), so if you have 3 drives in a RAID 5, then you only have 2 drives worth of space.. If you have 4 drives in the RAID, then you have 3 disks worth of space..  

FE
Fatal_ExceptionSystems Engineer
Top Expert 2005

Commented:
Additionally, RAID 5 offers much better performance than a mirrored drive...  forgot to put that in...  Because it is striping the drives with data, the speeds are much, much better..

here is an overview of RAID 5..  note the last paragraph..

http://www.pcguide.com/ref/hdd/perf/raid/levels/singleLevel5-c.html

FE

Author

Commented:
so let's say that the 2nd drive of the raid fails, Am'I able to install a new drive and recovery the data that was on the bad drive? Or I lost the entire raid thing and my data?

Thanks
jdff

Author

Commented:
Also,
Isn't dynamic partitions faster than basic?

Thanks
jdff

Commented:
jdff,

For the best read/write speeds RAID 1 is bettter that RAID 5

If three disks is all you have then your current suggestion is the best option (System disk RAID 0 and 2 data disks RAID 1)
If you had four disks  - 2 System disk RAID 1 and 2 data disks RAID 1
If you had five disks - 2 System disk RAID 1 and 2 data disks RAID 1 + 1 disk as hot swap or 2 System disk RAID 1 and 3 data disks RAID 5

This should help firm up what the different types of RAID are for:
http://www.melbpc.org.au/pcupdate/2306/2306article6.htm


Ms Dynamic disks have the following advantages:

http://www.microsoft.com/windows2000/en/server/help/default.asp?url=/windows2000/en/server/help/sag_DISKconcepts_04A.htm


My personal view is that RAID 5 is the way to go with data as it's fault tolerent and expandable. Most of the data i put on RAID 5 disks doesn't need masive read/write speeds (usually MS office files).
 I use RAID 1 for system disks and log files (Exchange/SQL) for the speed factor.

Hope that helps!
Systems Engineer
Top Expert 2005
Commented:
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Fatal_ExceptionSystems Engineer
Top Expert 2005

Commented:
Here is a little on software RAID 5 when done within Windows..   Again, these must be dynamic...

http://www.winnetmag.com/Article/ArticleID/14675/Windows_14675.html

Author

Commented:
But what you do when one hard disk crashes out of raid 1 or 5? I would like to go ahead and use raid5 but the thing is that I think if one drive physically crashes it does not have the ability of bringing the files back on new replacement drive, Is this correct?


Thank you for your time.
jdff
Fatal_ExceptionSystems Engineer
Top Expert 2005

Commented:
BTW:  What90..  hope you do not mind me buttin in on this thread..  just bored tonight I guess...  :)
Fatal_ExceptionSystems Engineer
Top Expert 2005

Commented:
NO....  That is what RAID 5 is all about...   They definitely have that capability..!!!!!
Fatal_ExceptionSystems Engineer
Top Expert 2005

Commented:
Read that link I posted above, or the one W90 mentioned...  It is all about the parity stripe...!!  very cool, and highly recommended..!!

Author

Commented:
Ok, so now I understand a bit, so the RAID5 will regenerate the files into the new drive because the parity stripe. Is there any circumstances that raid5 will completely fail? Does every drive on RAID5 has the parity stripe of the other drives?

Thanks
jdff

Commented:
Fatal_Exception,
Missed you posts - damned QuickPost not refreshing ;-)

Have a great Easter!
Fatal_ExceptionSystems Engineer
Top Expert 2005

Commented:
Correct..  the parity stripe is created on all drives, meaning that when any one of the drives fails, it can be regenerated from the other drives...   Of course, if multiple drives fail, then you could be in trouble, but the chances of that are slim, and that is why we have backups, right..??
Fatal_ExceptionSystems Engineer
Top Expert 2005

Commented:
*grin*  I gave up on QP...  not that it did not do the job, but just did not want it running in front of me all the time...    I too missed some posts with it, so I just count on my email refreshing every minute... lol, eh..?

And happy Easter to all of you..!!

FE

Commented:
jdff,


Say you have 3 RAID 5 disks, then two of them fail - you can still regenerate the data for the last disk. You'd have to destroy the entire RAID 5 array (all 3 disks would have to fail) That why most of use love RAID 5!
Fatal_ExceptionSystems Engineer
Top Expert 2005

Commented:
:)  Next best thing to NEVER HAVING TO WORRY..!!!   Disaster Recovery can take years off an admins life..!!!  Knock on wood..
Gareth GudgerSolution Architect
CERTIFIED EXPERT
Most Valuable Expert 2014
Top Expert 2014

Commented:
Actually I thought only one disk was allowed to fail in RAID 5?

Commented:
diggisaur - your correct, but obviously depending on the RAID 5 disk numbers.

I've seen a 3 disk RAID 5 array lost two drives, which stopped it being operational but the data was recovered from last good disk and the RAID array was rebuilt. Jusy one of the reason I convince the money men to spend that little bit more on data protection from RAID 5.
Fatal_ExceptionSystems Engineer
Top Expert 2005

Commented:
And what are the chances that 2 drives are going to fail at once..??   It would have to be something major, like a tremendous power spike, which is unlikely if you are using good protection and a UPS....   The parity stripe keeps info on everything that goes on the disk array, so the entire array can be rebuilt..  and obviously, the more disks, the better..

I even like to put 'hot spares' in my servers, which just sit there until needed..  And the good servers come with SCSI arrays that are hot swappable..  meaning you can replace the drives on the fly..  

Good morning everyone..!!  

Commented:
jdff,

Did you make a choice on what was best for you?
What did you choose?
Fatal_ExceptionSystems Engineer
Top Expert 2005

Commented:
Thanks..  glad we could help..

FE

Author

Commented:
What90 thank you very much also for your time and explanation, I accepted FE's comment cause that one was very clear on what I was trying to understand. You did a great job also and I'm sure you'll be able to help me another time.

Thanks
jdff

Commented:
No problem, my spelling and typing skills stink, so I prefer to cut and paste links rather than confuse the buggery out of folks trying to follow my personal instructions ;-)
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