SCSI vs IDE

SCSI vs IDE

[Linux Explorer]

[-- Attachment #1: Type: text/plain, Size: 740 bytes --]

Hi,

I am using SCSI disk for backup operation, and I found
out that it takes long time than IDE disk.

Herewith I attach the two text files they give the
time taken for SCSI and IDE disks for writing 4728MB
of data using dd command.

Can anyone tell me , why SCSI disk takes approximately
3 times as IDE disk?

Herewith I attach one more text file inq.txt which
gives the Inquiry information of the attached scsi
disk.

I have tried this with adaptec and LSI logic scsi
controllers, both are taking same time.

Thanks in adavance.

Regards,
Linux Erfroschen

=====
Thanks and Regards,
Erforschen


		
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[-- Attachment #2: ide.txt --]
[-- Type: text/plain, Size: 158 bytes --]

[root@localhost root]# time dd of=/dev/hda4 if=/dev/zero bs=1024k count=4728
4728+0 records in
4728+0 records out

real	2m24.942s
user	0m0.010s
sys	0m11.200s

[-- Attachment #3: scsi.txt --]
[-- Type: text/plain, Size: 412 bytes --]

[root@localhost root]# time dd of=/dev/sda if=/dev/zero bs=1024k count=4728 
4728+0 records in
4728+0 records out

real	6m54.500s
user	0m0.000s
sys	0m12.100s

[root@localhost root]# raw /dev/raw/raw1 /dev/sda
/dev/raw/raw1:	bound to major 8, minor 0

[root@localhost root]# time dd of=/dev/raw/raw1 if=/dev/zero bs=1024k count=4728
4728+0 records in
4728+0 records out

real	6m47.032s
user	0m0.010s
sys	0m6.160s

[-- Attachment #4: inq.txt --]
[-- Type: text/plain, Size: 2253 bytes --]

scu> 
Inquiry Information:

                Peripheral Device Type: 0 (Direct Access)
                  Peripheral Qualifier: 0 (Peripheral Device Connected)
                  Device Type Modifier: 0
                       Removable Media: No
                          ANSI Version: 2 (Complies to ANSI X3.131-1994, SCSI-2)
                          ECMA Version: 0
                           ISO Version: 0
                  Response Data Format: 2 (SCSI-2)
                 Terminate I/O Process: No
                     Additional Length: 159
                    Soft Reset Support: No
               Command Queuing Support: Yes
               Target Transfer Disable: No
                Linked Command Support: Yes
            Synchronous Data Transfers: Yes
          Support for 16 Bit Transfers: Yes
          Support for 32 Bit Transfers: No
           Relative Addressing Support: No
                 Vendor Identification: DEC     
                Product Identification: RZ1EF-CB (C) DEC
               Firmware Revision Level: 0372
                  Vendor Specific Data: 36 38 30 30 46 39 43 31 "6800F9C1"
                                        34 4b 4d 53 42 44 43 33 "4KMSBDC3"
                                        37 32 20 20 00 00 00 00 "72      "
                                        00 00 00 00 00 00 00 00 "        "
                                        00 00 00 00 00 00 00 00 "        "
                                        00 00 00 00 00 00 00 00 "        "
                                        00 00 00 00 00 00 00 00 "        "
                                        00 00 00 00 00 00 30 39 "      09"
                                        52 49 39 38 32 37 31 00 "RI98271 "
                                        30 30 30 31 32 32 30 38 "00012208"
                                        4c 39 34 38 36 20 20 20 "L9486   "
                                        20 20 46 32 32 38 30 32 "  F22802"
                                        20 20 20 20 51 35 39 48 "    Q59H"
                                        37 31 35 32 4d 30 32 00 "7152M02 "
                                        45 33 32 32 38 30 20 20 "E32280  "
                                        20 20 31 39 39 38 00 00 "  1998  "


scu> 

Re: SCSI vs IDE

[Douglas Gilbert]

Linux Explorer wrote:
> Hi,
> 
> I am using SCSI disk for backup operation, and I found
> out that it takes long time than IDE disk.
> 
> Herewith I attach the two text files they give the
> time taken for SCSI and IDE disks for writing 4728MB
> of data using dd command.
> 
> Can anyone tell me , why SCSI disk takes approximately
> 3 times as IDE disk?
> 
> Herewith I attach one more text file inq.txt which
> gives the Inquiry information of the attached scsi
> disk.
> 
> I have tried this with adaptec and LSI logic scsi
> controllers, both are taking same time.

It is good to see that Digital Equipment Corporation SCSI-2
disks are still going strong. So I guess it is not a Ultra
320 or SAS disk running at 15,000 rpm. Current SCSI disks
are approaching transfer speeds of 100 MB/sec while your
measurement shows a write speed of 11 MB/sec.

What vintage is the IDE (ATA) disk that you are using for
comparison? Your measurement shows a write speed of 33
MB/sec.

About the only thing that might be tweaked with your
hardware is write caching. ATA disks seem to have it
on all the time. For your SCSI disk, in scu try:
"show pages cache-control" and look at the "Write Cache Enable"
state. If it says "No" then use scu to set it to "Yes" and
retest.

Doug Gilbert

Re: SCSI vs IDE

[Ricky Beam]

On Mon, 30 Aug 2004, Linux Explorer wrote:
>Can anyone tell me , why SCSI disk takes approximately
>3 times as IDE disk?

Just a guess... that SCSI disk is 10 years older than your IDE disk.  You
have not provided any details about the hardware setup: controller for
both scsi and ide, cabling, other devices on the bus, model of the IDE
disk...

>I have tried this with adaptec and LSI logic scsi
>controllers, both are taking same time.

(btw, adaptec and lsi make/have made hundreds of controllers.)

--Ricky