# SCSI Disk Performance

## Tzuriel

Hey all, 

I was testing my new stage 1 installation w/ someone who was helping me out and I did an 'hdparm' test to check my disk access speeds (after the complete install). The results were that he thought I should have had way better times than what I've got. 

```

$ hdparam -tT /dev/sda

/dev/sda3 

Timing cached reads: 2748 MB in 2.00 seconds = 1373.52 MB/sec 

Timing buffered disk reads: 104 MB in 3.03 seconds = 34.27 MB/sec 

```

So for a Dell PowerEdge 1750 w/ an "Integrated dual channel Ultra 320" embedded SCSI controller and 10K RPM SCSI drives ... is something terribly wrong here? Have I possibly built my kernel wrong?

Here's some links I dug up with specifics on the hardware ...

http://www.dell.com/downloads/global/products/pedge/en/1750_brief.pdf

http://www.dell.com/downloads/global/products/pedge/en/1750_specs.pdf\

http://www1.us.dell.com/content/products/productdetails.aspx/pedge_1750?c=us&cs=28&l=en&s=dfb&~tab=specstab#tabtop

Any help much appreciated.

----------

## wmgoree

He's complaining about 1378 and 34? That sounds fine to me for a PowerEdge 1750.

I mean, I've got as much affection for my PowerEdges as the next guy, but the fact is these are "value" workhorses more than high-performance systems. 1378 / 34 is still twice as fast as any ATA drive you'll find. You could probably bring it up *some* by tweaking hdparm (incidentally, it's "hdparm" not "hdparam") or by getting new firmware for your SCSI controller, but at some point you have to ask if it's worth it. Unless you're doing hardcore journal-on-a-different-block-device kind of fine tuning you probably wouldn't notice much improvement.

----------

## Tzuriel

 *Quote:*   

> The first test line seems fine ... the second line is a bit low... did you try running this test a couple of times? 
> 
>                               EDIT: Actually, your test are quite low...especially the second one. I am using ATA133 and I get about 2x the speed that you get for the second
> 
>                               line. Your first line out-does my hdd by about 200 MB/sec. 
> ...

 

Yeah, I see your point if it only brings it up minimally. I just thought there might be a huge performance gain to work for since it seems normal drives are doing better than this.

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## overkll

 *wmgoree wrote:*   

> He's complaining about 1378 and 34? That sounds fine to me for a PowerEdge 1750.

 

wmgoree,

Complaining, no.  Puzzled, yes! tzuriel's drive is a U320, 10K rpm SCSI drive.  Maybe this system was priced very good, but usually SCSI drives are more expensive because they are deemed to be faster (seek times and thoughput), more reliable and have better waranties than PATA and SATA.

 *Quote:*   

> ...1378 / 34 is still twice as fast as any ATA drive you'll find. You could probably bring it up *some* by tweaking hdparm...

 

Oh contraire!  I have ATA/UDMA100 drives that post faster than that!

The first hdparm test is "Timing cache reads".  From what I can tell, this is more a function of available memory bandwith/frontside bus.  The second test is "Timing buffer disk reads" and is a good indicator of your drive's actual performace.  I know that hdparm isn't perfect, but the second test gives you a decent baseline to judge the drive's speed.  There are more accurate benchmarking tools.  IMHO, Hdparm is more of a quick and dirty check.

I've got 4 AMD based Gentoo systems with diffenent hardware and kernels.  I ran "hdparm" on all of them.  The results make me wonder why an expensive 10K U320 SCSI drive isn't faster.  For the record, I am NOT trying to prove that AMD is better than Intel.  I only have one Intel box, and it's running Windows ME.  BTW, I don't use any hdparm "tweaks" on these machines aside from making sure they are running in DMA mode.  This is by no means a scientific test.

AthlonXP 2800 (2Ghz), ATA/UDMA133, 512mb ram

OS = Gentoo, 2.4 series kernel

 *Quote:*   

> /dev/hde:
> 
>  Timing cached reads:   1968 MB in  2.00 seconds = 984.00 MB/sec
> 
>  Timing buffered disk reads:  122 MB in  3.04 seconds =  40.13 MB/sec

 

Dual AthlonMP 1800 (2x 1.4Ghz), ATA/UDMA100 768mb ram

OS = Gentoo, 2.4 series kernel

 *Quote:*   

> /dev/hda1:
> 
>  Timing cached reads:   1068 MB in  2.00 seconds = 534.00 MB/sec
> 
>  Timing buffered disk reads:  138 MB in  3.03 seconds =  45.54 MB/sec

 

Athlon64 3000+ (1.8Ghz, 939 pin), SATA150, 512mb ram

OS = Gentoo, x86 32bit mode, 2.6 series kernel

 *Quote:*   

> /dev/sda3:
> 
>  Timing cached reads:   3228 MB in  2.00 seconds = 1613.44 MB/sec
> 
>  Timing buffered disk reads:  184 MB in  3.00 seconds =  61.32 MB/sec

 

Athlon64 3500+ (2.2Ghz, 939 pin), !Gb ram

OS = Gentoo, x86_64 64bit mode, 2.6 series kernel

 *Quote:*   

> ATA/UDMA133
> 
> /dev/hde3:
> 
>  Timing cached reads:   4560 MB in  2.00 seconds = 2278.07 MB/sec
> ...

 

So, IMHO either SCSI doesn't perform as advertised (not likely) or something is preventing that U320 10K SCSI drive from better performance.  Maybe hdparm isn't suited to accurately gauge the performance of SCSI drives?

I may be wrong, and if I am, I welcome anyone to straighten me out in this issue.   34mb/sec for a 10K rpm U320 SCSI drive just seems too low to me.Last edited by overkll on Mon Jun 06, 2005 11:49 pm; edited 2 times in total

----------

## plut0

I like to use dd for read/write, test for 1gb file.

time dd if=/dev/zero of=test bs=1024 count=1048576

```
1048576+0 records in

1048576+0 records out

real    0m29.917s

user    0m0.469s

sys     0m13.255s
```

1000MB / 29.917s = 33.425 MB/s write

time dd if=test of=/dev/null bs=1024

```
1048576+0 records in

1048576+0 records out

real    0m23.620s

user    0m0.299s

sys     0m4.160s
```

1000MB / 23.620s = 42.337 MB/s read

That is pretty bad performance you're getting.  The one I just tested is a generic 5 year old IDE drive, most likely 7200rpm.

Are you using RAID by chance?

----------

## overkll

Pluto,

Ahhh!  Good idea!  I'm going to have to try the dd test.  Thanks.

----------

## kash04

did anyone find out anymore info on this? i'm getting the same results as him on my centos box.. maybe it is the poweredge :-\

an ide drive

aries akash # hdparm -tT /dev/hda3

/dev/hda3:

 Timing cached reads:   2792 MB in  2.00 seconds = 1396.21 MB/sec

 Timing buffered disk reads:  160 MB in  3.02 seconds =  53.01 MB/sec

and my scsi disk 

[root@asterisk1 ~]# hdparm -tT /dev/sda3

/dev/sda3:

 Timing cached reads:   2564 MB in  2.00 seconds = 1280.27 MB/sec

 Timing buffered disk reads:  142 MB in  3.00 seconds =  47.29 MB/sec

----------

## tomatopi

I have lots of servers with SCSI drives and hdparam always seems to show really low numbers when testing compared to ATA/SATA drives. It often shows me lower numbers on SCSI drives than old ATA laptop drives I test. I think SCSI excels more at low-overhead and high-transaction load than raw read-write speeds which is what hdparm seems to test. Overall, all the servers run smooth as silk even with supposidly low I/O rates.

----------

## plonka2000

Hi all,

Interesting thread regarding SCSI and SATA/PATA performance.

I have a bit of a cunnundrum of my own though, as I wanted to tweak my hdparm settings for my SATA drives but am unable to it seems.

Can anyone explain why I get errors with hdparm and my SATA drives?

I cant get hdparm settings from them. Is this normal?

Its running on an a8n-sli deluxe motherboard (AMD64) on a Silicon Image 3114 controller.

All drives are Maxtor Diamondmax 9 SATA 160GB.

Here are my outputs:

```
hdparm -tT /dev/sda /dev/sdb /dev/sdc /dev/sdd

/dev/sda:

 Timing cached reads:   3620 MB in  2.00 seconds = 1810.28 MB/sec

HDIO_DRIVE_CMD(null) (wait for flush complete) failed: Inappropriate ioctl for device

 Timing buffered disk reads:  170 MB in  3.01 seconds =  56.47 MB/sec

HDIO_DRIVE_CMD(null) (wait for flush complete) failed: Inappropriate ioctl for device

/dev/sdb:

 Timing cached reads:   3640 MB in  2.00 seconds = 1819.37 MB/sec

HDIO_DRIVE_CMD(null) (wait for flush complete) failed: Inappropriate ioctl for device

 Timing buffered disk reads:  170 MB in  3.01 seconds =  56.56 MB/sec

HDIO_DRIVE_CMD(null) (wait for flush complete) failed: Inappropriate ioctl for device

/dev/sdc:

 Timing cached reads:   3652 MB in  2.00 seconds = 1825.37 MB/sec

HDIO_DRIVE_CMD(null) (wait for flush complete) failed: Inappropriate ioctl for device

 Timing buffered disk reads:  170 MB in  3.01 seconds =  56.51 MB/sec

HDIO_DRIVE_CMD(null) (wait for flush complete) failed: Inappropriate ioctl for device

/dev/sdd:

 Timing cached reads:   3628 MB in  2.00 seconds = 1811.56 MB/sec

HDIO_DRIVE_CMD(null) (wait for flush complete) failed: Inappropriate ioctl for device

 Timing buffered disk reads:  172 MB in  3.03 seconds =  56.72 MB/sec

HDIO_DRIVE_CMD(null) (wait for flush complete) failed: Inappropriate ioctl for device
```

```
hdparm /dev/sda

/dev/sda:

 IO_support   =  0 (default 16-bit)

 readonly     =  0 (off)

 readahead    = 256 (on)

 geometry     = 19929/255/63, sectors = 163928604672, start = 0
```

```
hdparm -i /dev/sda

/dev/sda:

 HDIO_GET_IDENTITY failed: Inappropriate ioctl for device
```

----------

## augury

A scsi w/ performance comparable to sata or even fast ata drives tends to run expensive (DoD expensive).  I get about 35 MB/sec on fibre channel 10k cheetahs although this seems to be limited by either the pci bus or fibre interface (raid0 sees no improvement).  In comparison I've gotten 2 sata's in raid0 to do just under 120 MB/sec.  I got my fibre channel disk for free but it would have cost me 10k used and its close to being retired for being 400lbs. overbuilt.  For the same sata space I would pay about $300-400.

----------

## linuxtuxhellsinki

plonka2000,

Hdparm is not working correctly with sata-drives or at least all the options are not supported.

There's also sdparm for scsi-drives, but the options are different   :Confused: 

----------

## plonka2000

 *linuxtuxhellsinki wrote:*   

> plonka2000,
> 
> Hdparm is not working correctly with sata-drives or at least all the options are not supported.
> 
> There's also sdparm for scsi-drives, but the options are different  

 

Yeah I've been looking into that, and you're correct.

However, I've been wresting with my wireless card for the last few days... *sigh*

...so my hdparm/sdparm issues will be on hold.   :Sad: 

Thanks for the info tho.  :Smile: 

----------

