Mailing List Archive

Zhiqiang Ye wrote:

>hdd are connected on the same ide
>channel...This will not improve the IO speed, is it?
>
>

Right. It won't give you any speed advantage, but you will have a
larger filesystem.

As for the other configs, I don't think it would matter much either way.

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On 18:00 Wed 29 Sep , Zhiqiang Ye wrote:
> Which one will be better?

The set up with two raid raid members is the normal way to do this.

Setting up 4 partitions spread over two physical devices will just
increase software raid overheads & head thrashing, without any
benefit in terms of redundancy or performance.

> And furthermore, since hdc and hdd are connected on the same ide
> channel...This will not improve the IO speed, is it?

Yes it will. Modern UDMA devices can transfer data over the IDE bus at
100-133MB/sec. This is the theoretical maximum data throughput of the
*bus*, not the disks. Even the latest hard disks struggle to come
close to this figure for sustained, linear reads/writes. A more
typical figure is 20MB/sec, again for linear access. So you can attach
two ATA-133 drives to a single bus and still have over 80MB/sec of
headroom on the bus.

Cheers,

Bryn.



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Thanks a lot.

Yes, I have tested my several configurations.
The things agree with what you said.


> > And furthermore, since hdc and hdd are connected on the same ide
> > channel...This will not improve the IO speed, is it?
>
> Yes it will. Modern UDMA devices can transfer data over the IDE bus at
> 100-133MB/sec. This is the theoretical maximum data throughput of the
> *bus*, not the disks. Even the latest hard disks struggle to come
> close to this figure for sustained, linear reads/writes. A more
> typical figure is 20MB/sec, again for linear access. So you can attach
> two ATA-133 drives to a single bus and still have over 80MB/sec of
> headroom on the bus.
>
> Cheers,
>
> Bryn.
>
>
>
>
> --
> gentoo-user@gentoo.org mailing list
>
>

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On Wed, 29 Sep 2004, Zhiqiang Ye wrote:

> Dear all:
> I am constructing raid0 using two 80G ide harddisk. I have two
> strategies:

<snip>

> Which one will be better?
> And furthermore, since hdc and hdd are connected on the same ide
> channel...This will not improve the IO speed, is it?

This is pretty much a bad idea all around no matter how you slice it. I'd
do the 80/80 route if you're set on doing this.

Not only do you not get any performance improvement, but you're
likely to get much less performance with trying to write to both drives
continuously. And you make things a bit more complicated, get a 160GB
filesystem instead of two 80GB filesystems, and if either drive fails you
lose all your data.

Buy a $30 PCI IDE card with two channels on it so at least you get some
performance improvements.

kashani

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On Wed, 29 Sep 2004, Zhiqiang Ye wrote:

> Which one will be better?
> And furthermore, since hdc and hdd are connected on the same ide
> channel...This will not improve the IO speed, is it?

Are you using RAID-0 purely for performance reasons or are trying to get
some protection against data loss.

I ask because you should know that RAID 0 gives you no redundancy - if a
drive files the entire RAID array goes with it. Either use RAID 1 or if
you have more drives, RAID 5.

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Aj.
Sys. Admin / Developer

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On Thu, 30 Sep 2004, Ajai Khattri wrote:

> On Wed, 29 Sep 2004, Zhiqiang Ye wrote:
>
> > Which one will be better?
> > And furthermore, since hdc and hdd are connected on the same ide
> > channel...This will not improve the IO speed, is it?
>
> Are you using RAID-0 purely for performance reasons or are trying to get
> some protection against data loss.
>
> I ask because you should know that RAID 0 gives you no redundancy - if a
> drive files the entire RAID array goes with it. Either use RAID 1 or if
> you have more drives, RAID 5.

It's my understanding that if the master drive on the channel goes
it'll take the slave down as well. Which in a RAID 1 situation is less
than optimal.

kashani

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On Thu, 30 Sep 2004, Kashani wrote:

> It's my understanding that if the master drive on the channel goes
> it'll take the slave down as well. Which in a RAID 1 situation is less
> than optimal.

But your data would be intact. You can then remove the failed drive and
mount the drive as regular fs. RAID 0 stripes across the drives, so a
drive failure would hose all your data... many people would consider that
"less than optimal" from a data redundancy standpoint ;-)


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Aj.
Sys. Admin / Developer

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Kashani wrote:

> It's my understanding that if the master drive on the channel goes
> it'll take the slave down as well. Which in a RAID 1 situation is less
> than optimal.

some controllers allow you to have a slave on a channel with no master.
I've inherited many a system with a bootable cd-rom that was listed as
slave on the 2nd channel with no other drive on that channel.

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On Fri, 1 Oct 2004, Ajai Khattri wrote:

> On Thu, 30 Sep 2004, Kashani wrote:
>
> > It's my understanding that if the master drive on the channel goes
> > it'll take the slave down as well. Which in a RAID 1 situation is less
> > than optimal.
>
> But your data would be intact. You can then remove the failed drive and
> mount the drive as regular fs. RAID 0 stripes across the drives, so a
> drive failure would hose all your data... many people would consider that
> "less than optimal" from a data redundancy standpoint ;-)

Having the data is nice. Having the machine down until you
can fix it is not. I'm not arguing for RAID 0, but against running
ANY RAID on a single IDE channel. Especially when PCI IDE cards are
cheap.

kashani

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On Fri, 1 Oct 2004, Kashani wrote:

> Having the data is nice. Having the machine down until you
> can fix it is not. I'm not arguing for RAID 0, but against running
> ANY RAID on a single IDE channel. Especially when PCI IDE cards are
> cheap.

For IDE, you're better off buying a cheap IDE RAID card ;-)


--
ADVENT /ad'vent/ n.

The prototypical computer
adventure game, first designed by Will Crowther on the PDP-10
in the mid-1970s as an attempt at computer-refereed fantasy gaming,
and expanded into a puzzle-oriented game by Don Woods at Stanford
in 1976. (Woods had been one of the authors of
INTERCAL.) Now better known as Adventure, but the TOPS-10
operating system permitted only six-letter filenames. See also
vadding, Zork, and Infocom.

This game defined the terse, dryly humorous style since expected in
text adventure games, and popularized several tag lines that have
become fixtures of hacker-speak: "A huge green fierce snake bars
the way!" "I see no X here" (for some noun X). "You are in a
maze of twisty little passages, all alike." "You are in a little
maze of twisty passages, all different." The `magic words'
xyzzy and plugh also derive from this game.

Crowther, by the way, participated in the exploration of the
Mammoth &amp; Flint Ridge cave system; it actually has a
`Colossal Cave' and a `Bedquilt' as in the game, and the `Y2' that
also turns up is cavers' jargon for a map reference to a secondary
entrance.

ADVENT sources are available for FTP at
ftp://ftp.wustl.edu/doc/misc/if-archive/games/sou
There's a version implemented as a set of web scripts at
http://tjwww.stanford.edu/adventure/.


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On Fri, 1 Oct 2004, Ajai Khattri wrote:

> On Fri, 1 Oct 2004, Kashani wrote:
>
> > Having the data is nice. Having the machine down until you
> > can fix it is not. I'm not arguing for RAID 0, but against running
> > ANY RAID on a single IDE channel. Especially when PCI IDE cards are
> > cheap.
>
> For IDE, you're better off buying a cheap IDE RAID card ;-)
>

Feh. It's six of one half a dozen of the other. Most cheap IDE
RAID cards do the equivalent of stuffing the /etc/raidtab into local
nvram. Basically acts a frontend for software RAID and the performance is
the same.

kashani

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