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Old 07-24-2008, 01:51 PM
Matt
 
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Is there anyway to enable NCQ on CentOS 4.6? I guess anouther
question is on a somewhat high activity mail server with a single
SATA2 drive will it do any good?

Matt
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Old 07-24-2008, 04:26 PM
Scott Silva
 
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on 7-24-2008 6:51 AM Matt spake the following:

Is there anyway to enable NCQ on CentOS 4.6? I guess anouther
question is on a somewhat high activity mail server with a single
SATA2 drive will it do any good?

Matt
I doubt it will make a BIG difference, but you might be looking for trouble
running a highly active server of any kind on a single spindle.


--
MailScanner is like deodorant...
You hope everybody uses it, and
you notice quickly if they don't!!!!

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Old 07-24-2008, 04:35 PM
Matt
 
Default Native Command Queueing

>> Is there anyway to enable NCQ on CentOS 4.6? I guess anouther
>> question is on a somewhat high activity mail server with a single
>> SATA2 drive will it do any good?
>>
>> Matt
>
> I doubt it will make a BIG difference, but you might be looking for trouble
> running a highly active server of any kind on a single spindle.

Some decisions made in past are hard to undo down the road. Would
like to move to CentOS 64 5.x with RAID but moving everything too a
new box is a very severe pain. I have to move it to new IP space
shortly and hate the idea of that.

Matt
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Old 07-24-2008, 04:41 PM
John R Pierce
 
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Matt wrote:

Is there anyway to enable NCQ on CentOS 4.6? I guess anouther
question is on a somewhat high activity mail server with a single
SATA2 drive will it do any good?




most of the tests I've seen, the overhead of SATA NCQ exceeds any gains
and it ends up slower :-/

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Old 07-24-2008, 04:52 PM
Matt
 
Default Native Command Queueing

>> Is there anyway to enable NCQ on CentOS 4.6? I guess anouther
>> question is on a somewhat high activity mail server with a single
>> SATA2 drive will it do any good?
>>
>
>
> most of the tests I've seen, the overhead of SATA NCQ exceeds any gains and
> it ends up slower :-/

Isn't there something like disk i/o ladder in the linux kernel that
does about the same thing anyway? But how could it tell what physical
position the head is at and which is the closest next place to go?

Matt
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Old 07-24-2008, 06:21 PM
Scott Silva
 
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on 7-24-2008 9:35 AM Matt spake the following:

Is there anyway to enable NCQ on CentOS 4.6? I guess anouther
question is on a somewhat high activity mail server with a single
SATA2 drive will it do any good?

Matt

I doubt it will make a BIG difference, but you might be looking for trouble
running a highly active server of any kind on a single spindle.


Some decisions made in past are hard to undo down the road. Would
like to move to CentOS 64 5.x with RAID but moving everything too a
new box is a very severe pain. I have to move it to new IP space
shortly and hate the idea of that.

Matt
You could easily move to a software raid1 with very little downtime and a few
reboots. It might also help slightly with read latencies, but wouldn't help
with writes.


--
MailScanner is like deodorant...
You hope everybody uses it, and
you notice quickly if they don't!!!!

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Old 07-24-2008, 07:56 PM
Guy Boisvert
 
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Scott Silva wrote:

on 7-24-2008 6:51 AM Matt spake the following:

Is there anyway to enable NCQ on CentOS 4.6? I guess anouther
question is on a somewhat high activity mail server with a single
SATA2 drive will it do any good?

Matt
I doubt it will make a BIG difference, but you might be looking for
trouble running a highly active server of any kind on a single spindle.




I have a Communigate mail server that was running on a single WD 200
Gigs IDE (7200 RPM). Communigate uses separate mbox files for storage,
very easy for backup / restore.


I was monitoring it with SAR and there was very high level of IOWait,
meaning the drive was having a hard time.


Context:
========
35 Users Running Outlook with Communigate MAPI Plugin
80 Gigs dataset (Total)
Public folder with about 50 Gigs of stuff

We replaced the server with a Tyan Transport TA-26. We put an Adaptec
3405 (4 ports Unified SATA/SAS adapter) and 4 Seagate 15K SAS 73 Gigs
drives (RAID 10). No more iowaits even if now there is 50 users.


I don't know about your context but running on a single drive is
dangerous for data loss anyway.


Hope this helped!


Guy Boisvert, ing.
IngTegration inc.
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Old 07-24-2008, 11:21 PM
Matt
 
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>>I was monitoring it with SAR and there was very high level of IOWait, meaning the drive was having a hard time.

How bad does the below look? Dual core AM2 5600+ with 4G DDR2 and
single SATA2 drive.

Matt

10:10:01 AM all 20.54 0.00 4.09 15.85 59.52
10:20:01 AM all 19.96 0.00 4.17 16.81 59.06
10:30:01 AM all 15.94 0.00 2.48 14.78 66.80
10:40:01 AM all 14.15 0.00 3.62 13.13 69.11
10:50:01 AM all 13.77 0.00 3.53 13.52 69.18
11:00:02 AM all 13.71 0.00 2.24 12.33 71.73
11:10:01 AM all 14.42 0.00 3.51 13.19 68.88
11:20:01 AM all 12.32 0.00 3.37 11.74 72.57
11:30:01 AM all 13.93 0.00 2.54 16.23 67.30
11:40:01 AM all 14.59 0.00 3.68 11.27 70.46
11:50:01 AM all 12.74 0.00 3.27 11.18 72.81
12:00:01 PM all 10.75 0.00 1.71 9.68 77.86
12:10:01 PM all 13.32 0.00 3.26 12.21 71.21
12:20:01 PM all 11.91 0.00 3.86 12.84 71.40
12:30:01 PM all 13.89 0.00 2.33 11.74 72.04
12:40:01 PM all 10.78 0.00 3.13 10.23 75.86
12:50:01 PM all 10.78 0.00 3.07 9.47 76.68
01:00:01 PM all 9.44 0.00 1.72 10.24 78.60
01:10:01 PM all 12.45 0.00 3.34 10.54 73.66
01:20:01 PM all 12.14 0.00 3.46 11.44 72.97
01:30:01 PM all 18.43 0.00 2.64 13.01 65.92
01:40:01 PM all 14.97 0.00 3.54 11.34 70.14
01:50:02 PM all 11.42 0.00 3.16 9.36 76.06
02:00:01 PM all 10.74 0.00 1.81 8.49 78.96
02:10:01 PM all 10.37 0.00 3.02 7.47 79.14
02:20:02 PM all 11.69 0.00 3.49 9.86 74.96
02:30:01 PM all 8.71 0.00 1.62 7.40 82.27
02:40:01 PM all 9.92 0.00 3.21 8.60 78.26
02:50:02 PM all 9.11 0.00 3.08 9.20 78.60
03:00:01 PM all 12.38 0.00 2.12 11.28 74.22
03:10:01 PM all 12.17 0.00 3.38 9.51 74.94
03:20:01 PM all 10.21 0.00 3.17 10.73 75.90
03:30:01 PM all 13.11 0.00 2.51 16.24 68.13
03:40:01 PM all 13.11 0.00 3.22 8.39 75.28
03:50:01 PM all 9.08 0.00 2.92 7.47 80.54
04:00:02 PM all 7.51 0.00 1.43 5.94 85.12
04:10:02 PM all 11.25 0.00 3.23 10.89 74.63
04:20:01 PM all 12.52 0.00 3.62 9.57 74.29
04:30:01 PM all 9.07 0.00 1.61 6.85 82.47
04:40:02 PM all 8.86 0.00 2.80 7.74 80.61
04:50:01 PM all 8.37 0.00 2.80 6.67 82.16
05:00:01 PM all 9.10 0.00 1.38 6.17 83.34
05:10:01 PM all 10.93 0.00 3.01 6.24 79.81
05:20:01 PM all 8.60 0.00 3.48 7.52 80.40
05:30:01 PM all 7.37 0.00 1.44 6.14 85.04
05:40:01 PM all 10.30 0.00 3.03 6.79 79.88

05:40:01 PM CPU %user %nice %system %iowait %idle
05:50:01 PM all 7.20 0.00 2.49 5.08 85.23
Average: all 14.13 0.00 3.12 14.85 67.90
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Old 07-24-2008, 11:28 PM
"nate"
 
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Matt wrote:

> How bad does the below look? Dual core AM2 5600+ with 4G DDR2 and
> single SATA2 drive.
[..]
> 05:40:01 PM CPU %user %nice %system %iowait %idle
> 05:50:01 PM all 7.20 0.00 2.49 5.08 85.23
> Average: all 14.13 0.00 3.12 14.85 67.90

The average looks average.. with stats only collecting once every
10 minutes it's hard to say. I collect my stats using sar and pipe
them into cacti every minute.

If you get say into the 25-30% range I'd be concerned.

What kind of mail system are you running ? Is it simply a SMTP relay
or is mail being stored on the system and users accessing it? If
users are accessing it what type of mail storage(mbox, maildir, cyrus
etc).

nate

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Old 07-24-2008, 11:42 PM
Scott Silva
 
Default Native Command Queueing

on 7-24-2008 4:21 PM Matt spake the following:

I was monitoring it with SAR and there was very high level of IOWait, meaning the drive was having a hard time.


How bad does the below look? Dual core AM2 5600+ with 4G DDR2 and
single SATA2 drive.

Matt


<snip>


05:40:01 PM CPU %user %nice %system %iowait %idle
05:50:01 PM all 7.20 0.00 2.49 5.08 85.23
Average: all 14.13 0.00 3.12 14.85 67.90
User and IOwaits are a little high. Not going to stop the server, but it stops
it from hitting its full potential.

How many users?
I have a server with about 80 users and my averages are;

Average: all 6.00 0.00 3.65 3.95 86.40
That is with 2 dualcore XEON's at 2.2 Gh and 4 gigs and a SATA raid 5 (3ware)..
It was on a single drive for a month or so after a recovery and I had IOwaits
like yours. System was sluggish. Users whined. It wasn't pretty. The single
drive was the fastest recovery while I had to replace some drives that tanked.
I have a spare, but not 3.




--
MailScanner is like deodorant...
You hope everybody uses it, and
you notice quickly if they don't!!!!

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