[CentOS] Re: raid5 crash

[Bryan J. Smith]

On Sat, 2005-07-09 at 16:58 -0500, Aleksandar Milivojevic wrote:
> How often you get raid controller card go wrong (or any other PCI card 
> for that matter)?  Sure, if you are careless when handling it and static 
> electricity that accumulated in your body fries it.  Those installed in 
> production servers, very darn close to never.

GPU and MACs (NIC ICs) tend to be very high density and under-cooled.
They are solid state devices that tend to belly up in 3-5 years.

3Ware's ASIC, SRAM and ATA logic are rather low-density, and are always
cold to the touch in my experience.  Hence why I have _never_ seen the
fail -- and I'm talking dozens upon dozens of cards deployed.

> Even with that, if you keep a number of servers running, you usually 
> standardize on the cards you use (for example, you go with 3ware and 
> stick with them, or you go with Adaptec and stick with them).

Exactly.  I _never_ recommend just 1 device.  I'll standardize on
2+ servers or 2+ desktops with 3Ware cards.  E.g., even at home,
I have (2) 3Ware 7000 series and (4) 3Ware 6000 series.

I really hate it when I go into a department and they have a hodge-
podge of servers -- it's just a horrendously poor sign of configuration
management.  Money is _never_ a factor, it's how you use it, and I've
made do with far less than most.

Standardization is very key, even if it gets revised regularly or
you even change vendors a couple of times.  There are ways to deal
with those situations.

> Having a spare card or two in a drawer is a good idea anyhow, if you
> unexpectedly need to build the server overnight.

Well, when you're talking 4+ servers, you typically _should_ have a
"test" server which is also your "standby" server.  Right now in one
department in the organization I'm working with, that is their #1 issue.

[ I tire of having to do "new" things on production servers. ]

> And usually, you don't need to have exact same model of the card.
> In most cases, cards produced by one manufacturer can read RAID
> metadata information written by different card models (of the same
> manufacturer).

Not always.  Adaptec has had a nasty habit of buying other solutions
and ending up with 3-4 incompatible meta-data formats.  Even LSI Logic
has done this a few times too -- although far less because they are OEM
focused, not a retail vendor that customizes for OEMs (like Adaptec).

I've found 3Ware to be a company that has produced only their own
designs and meta-data format.  They are also very, very good on stating
when a firmware change does affect the meta-data format.  Their newer
firmware have _always_ allowed a newer firmware to read an older one.
3Ware's products are very proliferated.

While I understand the "risk" arguments made here, understand that
over my past 5+ years of 3Ware deployments, my clients and I have
undergone the _least_ risk thanx to 3Ware compared to other vendors
and solutions.  That's why I find most of the LVM/MD arguments that
may be applicable to _some_ vendors to be wholly inapplicable to
3Ware.

> So you can access your data as long as the replacement card has enough
> ports to connect all disks from failed card.

In the case of 3Ware, this has been 100% true.


-- 
Bryan J. Smith                                     b.j.smith at ieee.org 
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