Arch Linux

o1911

Member

From: Hobart, Australia

Registered: 2009-04-28

Posts: 106

Filesystems on RAID?

Hi there,

Been running arch64 for about 5 months now, very happy with it.  Until recently I've been using raid10 with ext4 as my / and I converted to XFS as I got a little fsck scare on a bad shutdown.  However switching from ext4 to XFS I've noticed some slowdowns...  I originally went with raid10 for the speed improvement without the worry of one drive dying and taking everything with it, so I want some of my performance back.

When I made the raid10 array, I didn't bother with the chunk size so it is default (64k).  I took a bit more care when I reformatted with XFS however; (pretty sure) I used sunit=128 and swidth=512 as they should be optimal.  As far as I can tell, XFS is generally better with larger files while ext4 is possibly just a little better with the smaller ones.  Bearing this in mind, I'm now considering splitting / and /home as the speed improvements I want (booting, program opening etc etc) would come from the / partition, so I was thinking of putting a 16k chunk size in mdadm for that array with ext4 and leaving 64k with XFS for /home.

Just wanted to know anyone's opinion before I committed

FWIW, CPU intensity shouldn't matter (Q6600 OCed from 2.4 to 3.51) and the HDDs are 4x WD6401AALS.

Thanks for any input

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Arch x86_64

dezza

Member

From: Denmark

Registered: 2007-04-05

Posts: 126

Re: Filesystems on RAID?

From where did you read how to calculate your chunk size?

Sounds like an interesting setup.

I have 6x 1TB disks, would someone recommend a kickass setup?

o1911

Member

From: Hobart, Australia

Registered: 2009-04-28

Posts: 106

Re: Filesystems on RAID?

From the man page, I think.   Also, I seem to remember a myth RAID article confirming what I input.

But yeah... my comp is no-where near as snappy as one would hope with my setup...

Once I buy a 1TB external HDD I'll backup my /home and start testing chunk sizes along with filesystems.  Hopefully a 40GB / with 16k chunk and ext4 is a winning combo.

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Arch x86_64

o1911

Member

From: Hobart, Australia

Registered: 2009-04-28

Posts: 106

Re: Filesystems on RAID?

Still haven't had the funds/time to try out my setup, but just wanted to know if anyone thinks this would work:

Can I raid0 my / (without home) across 4 drives and have that md device raid1'ed with another partition on a 5th drive?  Should one of my 4 drives die, I can just get the raid1 device on the 5th drive to copy my / back to the other 3.

Yes no maybe?

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Arch x86_64

fukawi2

Ex-Administratorino

From: .vic.au

Registered: 2007-09-28

Posts: 6,222

Website

Re: Filesystems on RAID?

It would work, but personally I wouldn't recommend it... It's messy...

     md0
    /   \
------------------------
  md1      /dev/sdd1
------------------------
    |
/dev/sda1
/dev/sdb1
/dev/sdc1

Personally, I'm a fan of making multiple RAID-1 array from some drives (for redundancy), then running LVM above that for the striping ("psuedo-raid0")

     lvmData
    /         \
------------------------
  md0           md1
------------------------
    |            |
/dev/sda1   /dev/sdb1
/dev/sdc1   /dev/sdd1

Last edited by fukawi2 (2009-08-23 09:11:36)

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