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Consultant Says Mirror is Better than RAID 5

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Consultant Says Mirror is Better than RAID 5 - 16.Nov.2005 2:40:45 AM   
2ndinfinity

 

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We hired an Exchange "expert" to advise us on the design of a new Exchange 2003 server for 400 mailboxes (73 GB current database size).

He said we should mirror the OS, the logs, and the database (total of 6 drives).

He said that RAID5 is just "wrong" and "old school."

Is this true?
Post #: 1
RE: Consultant Says Mirror is Better than RAID 5 - 16.Nov.2005 4:29:03 AM   
BeTaCam

 

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From: India
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Yes

The whole world is talking about IO's today and simple it it

RAID 5 = Read + (n-1).Write, so Read + 4 Writes

Whereas, RAID0 or RAID1+0 is not.

hth

/BC

(in reply to 2ndinfinity)
Post #: 2
RE: Consultant Says Mirror is Better than RAID 5 - 19.Nov.2005 11:19:29 PM   
nickpark

 

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quote:

ORIGINAL: 2ndinfinity

We hired an Exchange "expert" to advise us on the design of a new Exchange 2003 server for 400 mailboxes (73 GB current database size).

He said we should mirror the OS, the logs, and the database (total of 6 drives).

He said that RAID5 is just "wrong" and "old school."

Is this true?


Mirror if you have enough bays, but sometimes it pays to use raid5.
You will need *at least* 200gb for your db - you need 73GB for mail plus 73GB for a restore + growth.
So, to get 240GB - you'll need 6x78gb with mirroring. Or 4x78gb with raid5. (plus another drive for a hot spare.)
Or for 300GB, 4x150gb with mirroring and 3x150gb with raid5.
Or for 600GB, 8x150gb raid1 or 5x150gb raid5.

Add disks for a separate OS drive, separate logs drive and I'd look for storage with 20+ bays.

With 400 mailboxes, you're performance should be ok - I would concentrate more on risks and recovery.


(in reply to 2ndinfinity)
Post #: 3
RE: Consultant Says Mirror is Better than RAID 5 - 20.Nov.2005 9:44:37 PM   
Zelandakh

 

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If you do RAID5 against RAID1 as like for like, RAID1 is faster. But if the IO requirement is far short of the disk capacity, go for RAID5.

Also remember that once you go to E12, that issue goes away. For your size of store, RAID5 is probably the better way to go anyway.

(in reply to nickpark)
Post #: 4
RE: Consultant Says Mirror is Better than RAID 5 - 20.Nov.2005 10:01:59 PM   
johnkula

 

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For 400 users and 73GB store, Raid 5 is fine for performance.  I've run 800 users on a OS/Log Mirror (36GB) with the store running RAID5 (4 drives), with no disk issues.

For the size you are looking at, it's probably cheaper to go with mirrored drives, a pair of 146GB drives is pretty cost effective these days.

(in reply to Zelandakh)
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RE: Consultant Says Mirror is Better than RAID 5 - 20.Nov.2005 10:30:39 PM   
Zelandakh

 

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173GB disk = 161.1GB when formatted.
73GB store with enough room to eseutil/d means 73GB plus 7.3GB at the very least. That's 153.3GB which leaves 7.8GB spare or an expansion potential of just 3.7GB (5%).

I'd say that isn't sufficient these days. I'm predicting 100% growth per year of my store and would like to have 2 years of growth where possible.

(in reply to johnkula)
Post #: 6
RE: Consultant Says Mirror is Better than RAID 5 - 21.Nov.2005 9:46:09 AM   
mark@mvps.org

 

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I'd only tentatively concur. If you were going to have a single store that large then a RAID5 is your better solution /in your case and as you pose the question/. Although, that advice is not global for any random Joe reading this thread.

I'd like to bring up the store size here that everyone else has missed. You have a 73GB store. This means that you have either 2GB left before you top out or you have Enterprise Edition. If you're 2GB from the limit then we need to do something about that and the advice from Nick about your expandability isn't too valid. If you have Enterprise Edition then my advice is the following:
Use three mirrors. OS and Exchange on the first pair. Create 2SG's and place each of the logs on the other mirrors. Then create one mailbox in each SG and place them on the disk pair that the logs don't reside on. So SG1 Logs and Store 2 are on RAID1 Pair 2 and SG2 Logs and Store 1 are on RAID1 Pair 3. All nicely separate.
You're not going to have agro about I/O to be fair.

_____________________________

Mark Arnold (Exchange MVP)
List Moderator

(in reply to Zelandakh)
Post #: 7
RE: Consultant Says Mirror is Better than RAID 5 - 21.Nov.2005 11:31:32 PM   
Zelandakh

 

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Fair point Mark. I'd read it as total store size rather than one data store.

Now that I've re-read it, I concur with my learned colleague. Split yourself off 2 pairs of mirrored disks, each set holding a log set and a store set. If you lose anything you can get it back.

And DEFINITELY if you are running Exchange 2003 SP2 Standard, it is time for some serious housekeeping! Mind you, since the uplift from 16GB to 75GB was only possible from SP2 a month ago, that's some serious growth!

(in reply to mark@mvps.org)
Post #: 8
RE: Consultant Says Mirror is Better than RAID 5 - 12.Dec.2005 5:13:31 AM   
mcosy

 

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Joined: 14.Nov.2005
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Hi,

I got 150 users and Exchange 2003 Ent so thinking setup like this so please send your cmments.

2X 36GB : OS & Exchange

2x 36GB : Logs

2x 146GB : Data


(in reply to Zelandakh)
Post #: 9
RE: Consultant Says Mirror is Better than RAID 5 - 12.Dec.2005 10:16:11 AM   
jihadsoft

 

Posts: 7
Joined: 12.Dec.2005
Status: offline
 
Hi guys,

I am beginner with exchange server, Could you please explain the new way of fault tolrance instead of RAID5.

(in reply to mcosy)
Post #: 10

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