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Re: OT: 3Ware vs. Promise



On Thu, Nov 08, 2001 at 03:36:28PM -0800, nate wrote:
> David Priban said:
> > What exactly is the issue you are talking about?
> > I was just about to build a system using 6410 raid 5 :(
> >
> > Also couple of weeks ago 3ware announced it is going to
> > discontinue Escalade line of products. This makes me wonder
> > if this issue will ever get fixed.
> > Just checking 3ware website and the announcement is not there
> > any more. Just a broken link. I really hope they changed
> > their minds...
> 
> 
> well i don't know how to describe it. for a long time they had
> me confused wether it was IBM 75GXP drives causing problems or
> 3ware(turned out it was both). the western regional sales guy
> called me(and my boss) a couple months ago(at the request of
> my vendor) and told me the situation. not much details other then
> there is a known problem in the raid5 implimentation on all of
> their cards. they thought they had it fixed in the 7000 series
> which i recieved one, only to be later told do NOT use it as it
> apparently had a worse problem. one of my systems completely crapped
> out, and we dropped it off at the vendor, 3ware cameon site and looked at it(don't know what they did), they said
> they will have a fix soon(this was back in september), last
> i heard the fix was due mid november 2001. that to me doesn't
> mean it will work though. i have since switched from 4x80GB
> maxtors in RAID5 (was originally 4x75GB IBMs) to 6x80GB
> maxtors in raid 10. i asked my vendor to let me know in 6 months
> if the raid5 stuff on 3ware works and i will switch back
> then if it does.
> 
> the people at 3ware will probably admit to you if you contact
> them of the problem in raid5 i don't believe they are trying
> to keep it secret. their raid10 and raid0 systems apparently
> have been in running/production for about 18 months longer
> then raid5 and have no known problems.
> 
> i don't know the details of the problem in raid5 and can't
> really describe the symtoms as what i was suffering from was
> crappy disks(75GXP, had 5 fail in 30 days), and the raid
> card itself.

I remember reading about these problems a little while back when I was
considering using the 3ware raid cards - I too was very interested in
RAID 5. I may however got this mixed up with Promise - check reviews of
the cards for full accuracy!

From what I can remember, 3ware originally designed the cards for RAID
0, 1, 10 only. The hardware on the card can do these modes well and fast
as it is done properly in the logic on the card.

They then realised that the demand for RAID 5 was great and so kludged
together a software version - the XOR calculations were done by the
embedded OS on the card rather than the raw logic. Thus the performance
is much worse. Since then they've always been tweaking it to try to get
it to work properly - and as we've heard, it doesn't.

If you're going to be setting up a dedicated fileserver then you will
probably not get a severe performance hit if you just use software RAID
5 in the kernel - i've been using it here for some months with no
problems: just follow the HOWTOs and it's not really too difficult to
set up.

If you can afford it then go for a SCSI solution - it'll work. :-)

Matthew

-- 

Matthew Sackman
Nottingham,
ENGLAND

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