Re: [gentoo-amd64] Upgrading to Raid

[Joshua Hoblitt]

I have a large number (more then a dozen) 3Ware 8500 and 9500 cards.
The majority of these are 12-port SATA cards with RAID 5 volumes on
them.

Three quick observations:

* Software RAID 5 on Linux WILL NOT remap bad blocks/sectors like a
hardware RAID controller.  If you care about your data, software RAID
simply isn't an option.

* The RAID 5 performance of 3Ware controllers is terrible.  The 9500
series cards can push 50-55MB/s with xfs and in the neighborhood of
45MB/s with ext3 (with an enlarged journal, etc.) for sequential writes,
random I/O is even worse.  The 8500 cards are about 10% slower compared
to the 9500 once you fill up the on-card cache.

* Neither xfs or ext3 are reliable on volumes greater then 2TB.  Nor can
fdisk even partition them (but lvm2 can handle them).

Cheers,

-J

--
On Thu, Sep 01, 2005 at 12:36:08AM -0500, Francisco Perez wrote:
> Scott,
> I have a 3Ware Escalade 4 chaneel hardware raid controller running raid
> 10.  Here are my thoughts:  The card itself was $175.00 and the 4 250GB
> brives were $150 bucks a piece, so the cost is considerable.  If you are
> only going to have two disks mirrored, you can get the two channel card
> and two drives and mirror them which is obviously less money.  My system
> is a Tyan Transport GX-28 with 2 Opteron 246's and originally I had the
> drives on the onboard controller.  First, there is a very noticable
> increase in performance going from the integrated (software) raid
> controller to the hardware raid controller.  For my percieved needs it
> was definitely worth the money.  Second, its a nice reassurance to know
> that if a drive (or even two drives) fails the hardware controller can
> restore the array by popping in a new disk without me having to do
> much...I'm not sure if this is the case with the integrated or linux
> raid.  With the hardware controller, if I wanted a bit more storage
> space, I could have chosen to make a raid five array, something that as
> far as I know is unavailable in both integrated and Linux array (at
> least now without a significant performance hit.)  Hope that helps.
>
> Frank
>
> scotthathcock@×××××××.net wrote:
> >I currently have an ASUS K8V Deluxe system with an 80GB SATA drive. It
> >used to have a old 10GB PATA disk for M$ dual boot. That disk died and
> >was interfering with boot, so it's in the trash.
> >
> >The dead disk reminded me of the pain I will suffer if I loose my linux
> >system. Even with backups of my home dir, which I'm not as good about as
> >I should be, a full fresh install would be a pain. Thus, I am
> >considering Raid.
> >
> >Does anyone have experience with RAID on this Board?
> >Is the Via or Promise controller better for this?
> >Is there a good Howto on migrating from a non Raid disk to Raid? I
> >recall seeing one but can't find it now.
> >Am I wasting time and money? Should I just do a better job of backup? Is
> >there a resource on what to backup to allow a fast regeneration (or
> >duplication) of an existing gentoo system?
> >
> >Finally, thanks for the great distribution. I use a commercial distro at
> >work and I am much happier with Gentoo. :)
> >
> >Scott
> --
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