Re: [gentoo-server] RAID5 vs. RAID0+1

[Mike Williams]

On Friday 06 October 2006 18:20, Richard Broersma Jr wrote:
> I see from reading the mdadm man page that a RAID10 array can be created
> directly from individual drives.  I assume this gives better performance
> than creating two raid1 arrays and then using raid0 to attach the two raid1
> meta devices.  Is this the case?

Yup. I use it on 4 200GB drives (which 1 died a couple weeks ago, but I 
haven't got round to replacing) at home.
Can't say whether you'd get any better performance, but it's a whole lot 
easier to create and manage!

> Also, I notice when building new kernels that there are no kernel modules
> for RAID10.  I haven't yet tested this myself (although I have (4) 300GB on
> hand to start testing in the next few weeks), but would this create a
> problem when trying to create/mount a RAID10 meta device?

You'll need the kernel driver regardless.
What kernel? I was using RAID10 way back on 2.6.11.10 as a standard part of 
the kernel, I even found a bug which was fixed by a nice man from Suse within 
2 days (kernel.org bug#5181, hdf is the one which has properly failed now, I 
never did replace any after that bug).

> I had a terrible experience with my array when it was configured as raid5.
> It worked well for samba shares with lots of reads and few writes, but when
> I tried to use it in a heavy write environment,  the performance was
> terrible and the array would break and individual drive would become out of
> sync.  mdadm would of course automatically re-sync the drives once the
> writes completed.

Heh, I use RAID5 on the fileservers at work, and the backup box at our colo. 
The DBA is forever moaning at me that it's too slow for the DB backups, the 
fileservers are fine.

-- 
Mike Williams
-- 
gentoo-server@g.o mailing list