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List:       linux-admin
Subject:    Re: IDE Hardware RAID1 PDC20265
From:       "Shaf [Mobile]" <shaf () shaf ! net>
Date:       2001-12-30 20:25:30
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Mihai - I was trying to avoid having to do this, hence my initial enquiry ;)

OK Here goes... Tested software RAID1 with bonnie++ and was impressed by the \
figures... Then tried to use the same array set with the same kernel(2.14.17) with \
CONFIG_BLK_DEV_ATARAID_PDC et.al...... Completely screwed things up I could not be \
asked to recover the RAID ;)

So I ended up doing a fresh install of rh7.2 on a single disk /dev/hde(no software \
RAID)... Recompiled the kernel 2.14.17 with CONFIG_BLK_DEV_ATARAID_PDC etc  And \
booted this kernel off a floppy and managed to get the OS up...

HOWEVER looking at dmesg PDCRAID version was 0.03beta it managed to recognize my RAID \
setup(done after the install via the promise controller)but did do nothing with it ! \
The disks obviously needed syncing but no errors were generated ! I must have missed \
something maybe the md subsystem ? As it stands the kernel manages to mount \
/dev/ataraiod/d0p1 and recognized RAID1 configuration but the disk read/writes are to \
one disk only named /dev/hde.

I may have some more ideas to try to get this working but if anyone can throw over \
some suggestions all the merrier....

Noted : the ataraid howto specified that the driver is only RAID1 compatible ?

Many thanks in advance.
Shaf

Shaf - shaf@shaf.net -



-----Original Message-----
> From: "Mihai RUSU"<dizzy@roedu.net>
> Sent: 28/12/01 17:28:56
> To: "Shaf Ali"<shaf@shaf.net>
> Cc: "linux-admin@vger.kernel.org"<linux-admin@vger.kernel.org>
> Subject: Re: IDE Hardware RAID1 PDC20265
> 
> Hi
> 
> On Thu, 27 Dec 2001, Shaf Ali wrote:
> 
> > Out of curiousity whilst configuring 2.4.16 last night I noticed support for
> > PDC20265 in RAID mode, has anyone tried this out - will this be better than
> > software raid ?
> > 
> 
> usually hardware RAID its better but it depends VERY much on the chip
> included with the hard controller, also the performance difference depends
> on RAID modes used. usually you want RAID-5 (and other checksumming RAID)
> to run on hardware cards.
> 
> 
> > Currently using Software RAID1(Redhat 7.2 + 2.4.16) - works like a charm :
> > hot swapped the disk and added a new disk - hotraidadd and the new disk
> > rebuilt just fine.
> > 
> 
> somebody from the xfs-linux list said that he tested software raid and
> hardware raid with good hardware cards and he didnt got any performance
> boost for stripping raid modes (RAID-0) and mirroring (RAID-1)
> 
> he said he got some performance with RAID-5 BUT that depends on the
> controller (i dont think PDC are that good with RAID-5)
> 
> i think its best to try it yourself and give us feedback on this list
> (using bonnie++ like programs)
> 
> ----------------------------
> Mihai RUSU
> "... and what if this is as good as it gets ?"
> 
> 
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