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I'm using software mirror raid. (raid 0)
First hdd is more faster than second.
It is possible to configure raid to read from faster hdd?
Read speed from raid is < read speed from faster drive - Is it normal?)

pz wrote:
> I'm using software mirror raid. (raid 0)
> First hdd is more faster than second.
> It is possible to configure raid to read from faster hdd?
> Read speed from raid is < read speed from faster drive - Is it normal?)
>
>
No, it's not possible to have the OS read from the faster drive.
In raid0 (striping), you have the information broken up across both
drives so that when a read/write occurs, it only has to access half the
infomation (or less, depending on how many drives you have.
Here's the performance comparison I did between 2 setup's. First setup
is for a single IDE drive (WD 40gb with 8mb cache). Second setup is a
raid0 hardware array (Mylex 1100 card with 2 IBM SCSI U160 Ultrastar 9gb).
I've attached it as a file because it doesn't display correctly in such
a small window. As you can see, the difference is minimal for this
setup - probably because the mylex can only transfer at 80mb/sec TOPS
and the WD does 100 mb/sec (not really, but in theory). The biggest
difference is in Random Seeks and Sequential Input, but this is probably
due to the difference in scsi to ide. Although keep in mind the
difference in transfer rate maximum's, the raid0 is doing a bit better
even with having a handicap in the transfer rate. Having said all that,
it does go to show that the WD with 8mb cache is a heck of a drive.
Hope this will help a little.

SINGLE WESTERN DIGITAL WITH 8MB CACHE (40GB)

Version 1.03 ------Sequential Output------ --Sequential Input- --Random-
-Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks--
Machine Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP /sec %CP
ragingpenguin 1G 15876 95 40068 34 16912 15 17318 90 37395 11 142.7 0
------Sequential Create------ --------Random Create--------
-Create-- --Read--- -Delete-- -Create-- --Read--- -Delete--
files /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP
16 559 99 +++++ +++ +++++ +++ 602 99 +++++ +++ 2588 98

************************************************** **************************
************************************************** **************************

RAID0 - MYLEX 1100 CARD WITH 2 IBM ULTRASTARS (9.0GB)

Version 1.03 ------Sequential Output------ --Sequential Input- --Random-
-Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks--
Machine Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP /sec %CP
ragingpenguin 1G 16228 97 39776 33 17569 15 18881 97 47221 9 387.6 0
------Sequential Create------ --------Random Create--------
-Create-- --Read--- -Delete-- -Create-- --Read--- -Delete--
files /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP
16 575 99 +++++ +++ +++++ +++ 633 99 +++++ +++ 2609 98

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Hash: SHA1

On Fri, Oct 10, 2003 at 08:47:40AM PDT, pz wrote
in article <bm6kh6$94g$1@news2.ipartners.pl>:

> I'm using software mirror raid. (raid 0)

no you are not
if you were, you'd be doing raid 1

first make sure you understand what different raid levels do, then
implement the one you want. don't just do something, without knowing
what it is you're doing. if we wanted that, you could just be running
$THAT_OTHER_OS


Jurgen.

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psychopenguin <souza@psychopenguin.net> is thought to have
typed the following text on 2003-10-10:

> I've attached it as a file because it doesn't display correctly in such
> a small window. As you can see, the difference is minimal for this

Please don't do that, although everybody[0] should be able to read it
now, google won't archive it for future googlers.

I've quoted it here, so it will be archived.

#v+

> SINGLE WESTERN DIGITAL WITH 8MB CACHE (40GB)
>
> Version 1.03 ------Sequential Output------ --Sequential Input- --Random-
> -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks--
> Machine Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP /sec %CP
> ragingpenguin 1G 15876 95 40068 34 16912 15 17318 90 37395 11 142.7 0
> ------Sequential Create------ --------Random Create--------
> -Create-- --Read--- -Delete-- -Create-- --Read--- -Delete--
> files /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP
> 16 559 99 +++++ +++ +++++ +++ 602 99 +++++ +++ 2588 98
>
> ************************************************** **************************
> ************************************************** **************************
>
> RAID0 - MYLEX 1100 CARD WITH 2 IBM ULTRASTARS (9.0GB)
>
> Version 1.03 ------Sequential Output------ --Sequential Input- --Random-
> -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks--
> Machine Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP /sec %CP
> ragingpenguin 1G 16228 97 39776 33 17569 15 18881 97 47221 9 387.6 0
> ------Sequential Create------ --------Random Create--------
> -Create-- --Read--- -Delete-- -Create-- --Read--- -Delete--
> files /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP
> 16 575 99 +++++ +++ +++++ +++ 633 99 +++++ +++ 2609 98
>
>
#v-

[0] Since it's plain text.

- --
Bartosz Oudekerk

Play Rogue, visit exotic locations, meet strange creatures
and kill them.
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psychopenguin wrote:
> pz wrote:
>
>> I'm using software mirror raid. (raid 0)
>> First hdd is more faster than second.
>> It is possible to configure raid to read from faster hdd?
>> Read speed from raid is < read speed from faster drive - Is it normal?)
>>
>>
> No, it's not possible to have the OS read from the faster drive.
> In raid0 (striping), you have the information broken up across both
> drives so that when a read/write occurs, it only has to access half the
> infomation (or less, depending on how many drives you have.
> Here's the performance comparison I did between 2 setup's. First setup
> is for a single IDE drive (WD 40gb with 8mb cache). Second setup is a
> raid0 hardware array (Mylex 1100 card with 2 IBM SCSI U160 Ultrastar 9gb).
> I've attached it as a file because it doesn't display correctly in such
> a small window. As you can see, the difference is minimal for this
> setup - probably because the mylex can only transfer at 80mb/sec TOPS
> and the WD does 100 mb/sec (not really, but in theory). The biggest
> difference is in Random Seeks and Sequential Input, but this is probably
> due to the difference in scsi to ide. Although keep in mind the
> difference in transfer rate maximum's, the raid0 is doing a bit better
> even with having a handicap in the transfer rate. Having said all that,
> it does go to show that the WD with 8mb cache is a heck of a drive. Hope
> this will help a little.
>
>
> ------------------------------------------------------------------------
>
> SINGLE WESTERN DIGITAL WITH 8MB CACHE (40GB)
>
> Version 1.03 ------Sequential Output------ --Sequential Input- --Random-
> -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks--
> Machine Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP /sec %CP
> ragingpenguin 1G 15876 95 40068 34 16912 15 17318 90 37395 11 142.7 0
> ------Sequential Create------ --------Random Create--------
> -Create-- --Read--- -Delete-- -Create-- --Read--- -Delete--
> files /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP
> 16 559 99 +++++ +++ +++++ +++ 602 99 +++++ +++ 2588 98
>
> ************************************************** **************************
> ************************************************** **************************
>
> RAID0 - MYLEX 1100 CARD WITH 2 IBM ULTRASTARS (9.0GB)
>
> Version 1.03 ------Sequential Output------ --Sequential Input- --Random-
> -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks--
> Machine Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP /sec %CP
> ragingpenguin 1G 16228 97 39776 33 17569 15 18881 97 47221 9 387.6 0
> ------Sequential Create------ --------Random Create--------
> -Create-- --Read--- -Delete-- -Create-- --Read--- -Delete--
> files /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP
> 16 575 99 +++++ +++ +++++ +++ 633 99 +++++ +++ 2609 98
>

It is raid 1 - mirroring (my mistake)
Do you thing is better to use second machine and drbd or coda (or
something else) to assure speed (read speed) and "online" backup?

Thank you for help

PZ