[arch-general] RAID Configuration & Swap Space
I wanted to know if I configure my three identical disks as followed: - sda1 = /boot @ 4GB - sda2 = RAID @ 300GB - sdb1 = Swap @ 4GB - sdb2 = RAID @ 300GB - sdc1 = Swap @ 4GB - sdc2 = RAID @ 300GB Now when I am done configuring RAID, will Arch Linux show I have 8GB of Swap space total under a tool like 'htop' or something like this? Will the above configuration work? Or Should I change it?
On Wed, Mar 10, 2010 at 9:37 AM, Carlos Mennens <carloswill@gmail.com> wrote:
I wanted to know if I configure my three identical disks as followed:
- sda1 = /boot @ 4GB - sda2 = RAID @ 300GB
- sdb1 = Swap @ 4GB - sdb2 = RAID @ 300GB
- sdc1 = Swap @ 4GB - sdc2 = RAID @ 300GB
Now when I am done configuring RAID, will Arch Linux show I have 8GB of Swap space total under a tool like 'htop' or something like this? Will the above configuration work? Or Should I change it?
Yes, I tink it would work and you would get 8GB of swap. You are aware that if sda breaks, you loose the /boot partition and you can't boot anymore ? I would suggest creating a 100MB /boot partition on all 3 disks as a RAID 1 (4GB for boot is over kill IMHO). That way you can loose any disk and still be able to boot. Good luck -- Louis Brazeau Informaticien
On Wed, Mar 10, 2010 at 3:26 PM, Louis Brazeau <lbrazeau@gmail.com> wrote:
You are aware that if sda breaks, you loose the /boot partition and you can't boot anymore ? I would suggest creating a 100MB /boot partition on all 3 disks as a RAID 1 (4GB for boot is over kill IMHO). That way you can loose any disk and still be able to boot.
How would I create this via command line across three individual disks? Do you know that command would look like?
On Wed, Mar 10, 2010 at 11:11 AM, Carlos Mennens <carloswill@gmail.com> wrote:
On Wed, Mar 10, 2010 at 3:26 PM, Louis Brazeau <lbrazeau@gmail.com> wrote:
You are aware that if sda breaks, you loose the /boot partition and you can't boot anymore ? I would suggest creating a 100MB /boot partition on all 3 disks as a RAID 1 (4GB for boot is over kill IMHO). That way you can loose any disk and still be able to boot.
How would I create this via command line across three individual disks?
Do you know that command would look like?
You can use the RAID/LVM article on the wiki : http://wiki.archlinux.org/index.php/Installing_with_Software_RAID_or_LVM#Par... I used it in the past to setup a few systems with RAID and with or without LVM. So its your call if you want to use LVM or not. Also note that the article uses 3 swap partitions in a RAID 1 (total 2GB swap). So you will have to ajust the instructions for your situation. Anyway, it will give you a good idea what the commands look like. -- Louis Brazeau Informaticien
On Wed, Mar 10, 2010 at 4:25 PM, Louis Brazeau <lbrazeau@gmail.com> wrote:
You can use the RAID/LVM article on the wiki :
http://wiki.archlinux.org/index.php/Installing_with_Software_RAID_or_LVM#Par...
I used it in the past to setup a few systems with RAID and with or without LVM. So its your call if you want to use LVM or not.
Also note that the article uses 3 swap partitions in a RAID 1 (total 2GB swap). So you will have to ajust the instructions for your situation.
Anyway, it will give you a good idea what the commands look like.
Yes I am very familiar with that Wiki article but find Swap on RAID is useless, no? For my scenario I was going to do the following and please correct me if you think this is wrong: - sda1 = 100MB - sda2 = 1GB - sda3 = 300GB - sdb1 = 100MB - sdb2 = 1GB - sdb3 = 300GB - sdc1 = 100MB - sdc2 = 1GB - sdc3 = 300GB Then: mdadm --create /dev/md0 --level=1 --raid-devices=3 /dev/sda1 /dev/sdb1 /dev/sdc1 Then mount /boot on /dev/md0. Does that look correct or can I not do RAID1 on 3 devices? Should I have added '--spare-device=1' to that command? Now I would do: mdadm --create /dev/md1 --level=5 --raid-devices=3 /dev/sda2 /dev/sdb2 /dev/sdc2 Then mount / on /dev/md1. Do both commands look OK?
Carlos Mennens wrote:
Yes I am very familiar with that Wiki article but find Swap on RAID is useless, no? For my scenario I was going to do the following and please correct me if you think this is wrong:
It is useful if you want to continue running the system even with a failed disk (without a restart). Otherwise, yes. The kernel will distribute stores across swap disk if they all have the same priority. Depending on your bootloader support, you may want to use --metadata=1.0 on /boot to place raid metadata at the end and make it look like a normal partition. __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com
On Wed, Mar 10, 2010 at 11:44 AM, Carlos Mennens <carloswill@gmail.com> wrote: --snip--
Yes I am very familiar with that Wiki article but find Swap on RAID is useless, no? For my scenario I was going to do the following and please correct me if you think this is wrong:
- sda1 = 100MB - sda2 = 1GB - sda3 = 300GB
- sdb1 = 100MB - sdb2 = 1GB - sdb3 = 300GB
- sdc1 = 100MB - sdc2 = 1GB - sdc3 = 300GB
Then:
mdadm --create /dev/md0 --level=1 --raid-devices=3 /dev/sda1 /dev/sdb1 /dev/sdc1
Then mount /boot on /dev/md0. Does that look correct or can I not do RAID1 on 3 devices? Should I have added '--spare-device=1' to that command?
Now I would do:
mdadm --create /dev/md1 --level=5 --raid-devices=3 /dev/sda2 /dev/sdb2 /dev/sdc2
Then mount / on /dev/md1.
Do both commands look OK?
Yes, both look ok to me. -- Louis Brazeau Informaticien
On 03/10/2010 08:37 AM, Carlos Mennens wrote:
I wanted to know if I configure my three identical disks as followed:
- sda1 = /boot @ 4GB - sda2 = RAID @ 300GB
- sdb1 = Swap @ 4GB - sdb2 = RAID @ 300GB
- sdc1 = Swap @ 4GB - sdc2 = RAID @ 300GB
Now when I am done configuring RAID, will Arch Linux show I have 8GB of Swap space total under a tool like 'htop' or something like this? Will the above configuration work? Or Should I change it?
It will probably work, but I would change it. When I mirror a drive, I want "mirrored" drives (swap & boot included). For me, the purpose behind mirrored raid is to handle a drive failure. When one occurs, all I want to be required to do is reinstall grub on the remaining good drive, change fstab and reboot on a single drive until I get a replacement drive and then rebuild the array. Yes, I know if you just want disk redundancy for data storage, then you need not mirror the whole disk. But when swap is no more than 4 gig and /boot is no more than 150M, with at 750G drive the amount of data loss incurred due to mirroring a complete drive is less than 1% and for the convenience of instant recovery, it is worth it. -- David C. Rankin, J.D.,P.E. Rankin Law Firm, PLLC 510 Ochiltree Street Nacogdoches, Texas 75961 Telephone: (936) 715-9333 Facsimile: (936) 715-9339 www.rankinlawfirm.com
participants (4)
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Carlos Mennens
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David C. Rankin
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Linas
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Louis Brazeau