Re: New Server Revisted
- From: "John Fullbright [MVP]" <fjohn@donotspamnetappdotcom>
- Date: Tue, 6 Jun 2006 12:23:39 -0700
1. A 10K SATA drive is capable of about 40 random 4K IOs at a 20ms response
time. Compare this to 10K SCSI at about 85 IOPS and 15K SCSI at about 125.
2. From a performance perspective RAID 5 is the worst choice. combined
with SATA, you're bound to have performance problems.
Let's assume a 2:1 read write ratio.
RAID 5 write performance = P*N'/4 = 40*4/4 = 40 IOPS
RAID 5 read performance = P*N' = 40*4 = 160 IOPS
Apply the read/write ratio and 40*.33 + 160*.67 = 13 + 107 = 120
The RAID 5 array with 5 10K SATA drives is capable of 120 IOPS at an average
20ms response time, and there is no hot spare.
If you were to go RAID 10 with 4 drives:
RAID 10 write performance = P*N/2 = 40*4/2 = 80
RAID 10 read performance = P*N = 40*4 = 160
Applying the read/write ratio 80*.33 + 160*.67 = 26 + 107 = 133 IOPS at an
average 20ms response time and you do have a hot spare.
In a minimal Exchange depolyment, you would want three mirrors. Using your
SATA drives, each mirror would be capable of about 61 IOPS. The OS,
pagefile, and SMTP virtual directory would go on the first mirror. The logs
would go on the second mirror. The databases would go on the third mirror.
You are a drive short for the three mirror model. The OS, pagefile, and
SMTP directory will consume about 100 IOPS, so you have a problem.
I would recommend a single spindle for the OS and pagefile. This will give
you 40 IOPS.
Use a mirror for the logs, 61 IOPS. Use a second mirror for the databases,
and relocate your SMTP directories there - another 61 IOPS. Yes, you don't
have a pagefile, but with only 15 users this division should provide an
adequate level of performance. RAID 5 is out of the question if you value
your job. One big RAID 10 array is better from a performance perspective,
but you're really pushing the envelope.
"SPG" <nomail@xxxxxxxxxx> wrote in message
news:JRKfg.164$o4.69@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Back on May 7, 2006 I posted the following: "Getting a new server with 146
GB HD's only for Exchange Server 2003. Is there any logical reason why we
would want to partition the HD's since Exchange Server is the only thing
on this new server?". There were 10 responses with 7 telling what RAID
level and partitions to have. Only 3 gave me any insight as to why I
would want to partition this sucker. Here are the specs: We are a small
business with 10 users now and possibly going to 15 users (I told you we
were small!). The new server is a Dell PE1800, dual 3.2 Xeon processors, 2
GB memory and
3 - 160GB SATA Drives in RAID 5. I am tired of SCSI. The server is in
house, so lets not debate SCSI v. SATA. So, back to the original
question, why would we want to partition anything (I want redundancy) if
Exchange Server is the only thing running on this machine ?
Thanks,
SPG
.
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- New Server Revisted
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