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Old 11-03-2008, 09:51 PM
"Dotan Cohen"
 
Default Need help with raid layout

2008/11/3 Christopher Lemire <christopher.lemire@gmail.com>:
> I've been using Raid 1 for a while now. It increases my read speeds a little
> bit I guess, but I haven't had a hard drive fail where it ever did me any
> good. I just yanked a hard drive that was running in the raid out of my
> computer and watched Linux not crash and continue to run uninterrupted and
> also did simulated failures and rebuilding with mdadm. What I really want is
> performance. Raid 0 offers more performance than 5 and raid is not a backup
> solution, so what I want to do is this. Many people complains about raid 0,
> but I have an idea. I want cron jobs to run rsync for backups synchronizing
> my home folder to a new 640 gb Seagate hdd I'm looking at buying. The
> backups should be automated and done often, so, I can have @reboot in my
> crontab and rsync run by cron at times I am not likely to be doing anything
> or much with my computer. And if rsync only has to copy only new or modified
> files, it shouldn't take long at all to perform a backup and maybe I can
> have it run ever 3 hours or whenever the computer has been idle for 15
> minutes. I don't know how to do that except I think
> gnome-screensaver-command could check if the screensaver is active and if it
> is, I'm not using my computer, and rsync could go to work backuping up my
> files. The two drives I'm using for raid 1 right now that I want to
> reinstall Ubuntu 8.10 with raid 0 with are both identical sata2 Seagates 320
> gb drives. I want the partitioning scheme to be identical on both, but how
> would I do that if grub can't boot a Linux kernel that's in raid 0? I've
> made a /boot partition and put it in Raid 1 before but people have told me
> that its bad to have to have raid 1 and raid 0 that way and my performance
> would be lost, so how can I keep both drives with the same partitioning
> layout with Raid 0?
>

I'd keep the boot partition on sda and leave the corrosponding
partition on sdb empty. Or, you could have that partition on sdb as
swap. I don't think that you need to RAID swap if your goal is data
redundancy. Just RAID the data partitions.

--
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Old 11-04-2008, 01:23 AM
Rashkae
 
Default Need help with raid layout

Christopher Lemire wrote:

> would I do that if grub can't boot a Linux kernel that's in raid 0? I've
> made a /boot partition and put it in Raid 1 before but people have told me
> that its bad to have to have raid 1 and raid 0 that way and my performance
> would be lost, so how can I keep both drives with the same partitioning
> layout with Raid 0?
>
>


People are stupid. (or, more likely, they didn't understand what you
were trying to do).

You will have no performance penalty for making your /boot raid 1, but
you also gain absolutely no advantage, since the system won't boot if a
hard drive fails. You might as well just use those 20MB (or however
many MB you make boot) on the second hard drive as an empty partition.
But if you really wanted to make all partitions on both hard drives the
same, then by all means, RAID 1 your /boot, Raid 0 /, create a couple
swap partitions (one on each hard drive, do not RAID these) and away you go.

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Old 11-04-2008, 06:35 AM
Neil
 
Default Need help with raid layout

On Mon, Nov 3, 2008 at 10:59 PM, Christopher Lemire
<christopher.lemire@gmail.com> wrote:
> I've been using Raid 1 for a while now. It increases my read speeds a little
> bit I guess, but I haven't had a hard drive fail where it ever did me any
> good. I just yanked a hard drive that was running in the raid out of my
> computer and watched Linux not crash and continue to run uninterrupted and
> also did simulated failures and rebuilding with mdadm. What I really want is
> performance. Raid 0 offers more performance than 5 and raid is not a backup
> solution, so what I want to do is this. Many people complains about raid 0,
> but I have an idea. I want cron jobs to run rsync for backups synchronizing
> my home folder to a new 640 gb Seagate hdd I'm looking at buying. The
> backups should be automated and done often, so, I can have @reboot in my
> crontab and rsync run by cron at times I am not likely to be doing anything
> or much with my computer. And if rsync only has to copy only new or modified
> files, it shouldn't take long at all to perform a backup and maybe I can
> have it run ever 3 hours or whenever the computer has been idle for 15
> minutes. I don't know how to do that except I think
> gnome-screensaver-command could check if the screensaver is active and if it
> is, I'm not using my computer, and rsync could go to work backuping up my
> files. The two drives I'm using for raid 1 right now that I want to
> reinstall Ubuntu 8.10 with raid 0 with are both identical sata2 Seagates 320
> gb drives. I want the partitioning scheme to be identical on both, but how
> would I do that if grub can't boot a Linux kernel that's in raid 0? I've
> made a /boot partition and put it in Raid 1 before but people have told me
> that its bad to have to have raid 1 and raid 0 that way and my performance
> would be lost, so how can I keep both drives with the same partitioning
> layout with Raid 0?
>
> --
> Christopher Lemire <christopher.lemire@gmail.com>
> Fedora 64 bit Linux Raid Level 1
>
> --
> ubuntu-users mailing list
> ubuntu-users@lists.ubuntu.com
> Modify settings or unsubscribe at:
> https://lists.ubuntu.com/mailman/listinfo/ubuntu-users
>
>


hi

I had a quite good experience with mdRAID 0 on Suse once, and I guess
it will be possible on Ubuntu aswell, and it is easily tested. You can
simply set them up as raid using the bios and other mobo specific
things and run the live CD. If it recognises them you can install on
them.

Mdraid is the driver for FAKEraid. FAKEraid can be described as a
softraid that is recognised by the BIOS. You can't boot from a
softraid, you can from hard or mdraid, but the performance lose will
be bigger on mdraid as on hard raid. Hard raid is expensive, while
FAKEraid is common on newer mobos

You can also create a softraid with a separate (non raid) /boot
partition, but I'd advise to do this if mdraid fails.

Per defenition the partitioning you have now will be lost when you
switch to RAID0.

Do you know what RAID 0 is?

Neil

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Old 11-04-2008, 08:07 PM
Rashkae
 
Default Need help with raid layout

Neil wrote:

>
> hi
>
> I had a quite good experience with mdRAID 0 on Suse once, and I guess
> it will be possible on Ubuntu aswell, and it is easily tested. You can
> simply set them up as raid using the bios and other mobo specific
> things and run the live CD. If it recognises them you can install on
> them.

Unless you plan on investing in real raid hardware (with cpu and all
that), the cheapo mobo solutions are best avoided.. stick with software
raid.

>
> Mdraid is the driver for FAKEraid. FAKEraid can be described as a
> softraid that is recognised by the BIOS. You can't boot from a
> softraid, you can from hard or mdraid, but the performance lose will
> be bigger on mdraid as on hard raid. Hard raid is expensive, while
> FAKEraid is common on newer mobos

This was the common wisdom in the 486 days. Modern systems should have
more than enough CPU to handle Raid without noticeable performance hit.




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Old 11-11-2008, 08:39 AM
"Christopher Lemire"
 
Default Need help with raid layout

Swap should only be in raid if using redundancy because the system won't crash if a drive with swap goes down (I've tested this myself). The kernel does striping on its own if you give the swap partitions the same priority in /etc/fstab (see tldp.org on software raid), so no need for swap to be in raid 0.


On Mon, Nov 3, 2008 at 4:51 PM, Dotan Cohen <dotancohen@gmail.com> wrote:

2008/11/3 Christopher Lemire <christopher.lemire@gmail.com>:

> I've been using Raid 1 for a while now. It increases my read speeds a little

> bit I guess, but I haven't had a hard drive fail where it ever did me any

> good. I just yanked a hard drive that was running in the raid out of my

> computer and watched Linux not crash and continue to run uninterrupted and

> also did simulated failures and rebuilding with mdadm. What I really want is

> performance. Raid 0 offers more performance than 5 and raid is not a backup

> solution, so what I want to do is this. Many people complains about raid 0,

> but I have an idea. I want cron jobs to run rsync for backups synchronizing

> my home folder to a new 640 gb Seagate hdd I'm looking at buying. The

> backups should be automated and done often, so, I can have @reboot in my

> crontab and rsync run by cron at times I am not likely to be doing anything

> or much with my computer. And if rsync only has to copy only new or modified

> files, it shouldn't take long at all to perform a backup and maybe I can

> have it run ever 3 hours or whenever the computer has been idle for 15

> minutes. I don't know how to do that except I think

> gnome-screensaver-command could check if the screensaver is active and if it

> is, I'm not using my computer, and rsync could go to work backuping up my

> files. The two drives I'm using for raid 1 right now that I want to

> reinstall Ubuntu 8.10 with raid 0 with are both identical sata2 Seagates 320

> gb drives. I want the partitioning scheme to be identical on both, but how

> would I do that if grub can't boot a Linux kernel that's in raid 0? I've

> made a /boot partition and put it in Raid 1 before but people have told me

> that its bad to have to have raid 1 and raid 0 that way and my performance

> would be lost, so how can I keep both drives with the same partitioning

> layout with Raid 0?

>



I'd keep the boot partition on sda and leave the corrosponding

partition on sdb empty. Or, you could have that partition on sdb as

swap. I don't think that you need to RAID swap if your goal is data

redundancy. Just RAID the data partitions.



--

Dotan Cohen



http://what-is-what.com

http://gibberish.co.il

א-ב-ג-ד-ה-ו-ז-ח-ט-י-ך-כ-ל-ם-מ-ן-*-ס-ע-ף-פ-ץ-צ-ק-ר-ש-ת



ä-ö-ü-ß-Ä-Ö-Ü

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Christopher Lemire <christopher.lemire@gmail.com>
Fedora 64 bit Linux Raid Level 1

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