SATA Raid

[Dave Cramer]

On 18-Jun-06, at 1:52 PM, CLIFFORD ILKAY wrote:

> On June 17, 2006 23:50, Dave Cramer wrote:
>> On 17-Jun-06, at 8:06 PM, Robin Humble wrote:
>>> On Fri, Jun 16, 2006 at 08:51:45PM -0400, Dave Cramer wrote:
>>>> The areca cards are quite good
>>>
>>> are they faster than software raid5?
>>
>> Well, there are other things besides speed. Hotswapping, battery
>> backup, write cache, etc
>
> A counterpoint: hardware RAID is too dependent on your hardware being
> supported by the specific version of the kernel module. The MegaRAID
> fiasco is a good example. I have two servers that have MegaRAID SCSI
> controllers which were both running pre 2.6.9 kernels. I had added
> some new drives to the machines and had reconfigured the RAID volumes
> thus (knowingly) blowing away all the data on the drives. I figured I
> might as well install a modern distro. Imagine my surprise to find
> that my previously well-supported RAID controller was no longer
> automatically detected. I tried various distros thinking that the
> packagers of first one I tried might have screwed things up but none
> I tried, other than distros running pre 2.6.9 kernels, detected any
> volumes. A bit of digging and I found that for some reason, the
> megaraid modules had been renamed and were no longer included, if
> memory serves. We're not talking about some exotic or ancient
> technology that could be deprecated without having much of an impact.
> We're talking about one of the more popular SCSI RAID controllers on
> the market. Fortunately, I had no data riding on this.
>
> During the course of searching for answers, I found some convincing
> arguments as to why hardware RAID was potentially dangerous so I've
> been happily using software RAID since. Performance? Don't know,
> don't care. It's "fast enough" but I am reasonably sure now that a
> kernel upgrade isn't going to render my machine unusable.
>
>> I've heard that software raid was fast, or faster, but I still use
>> hardware raid cards, for the above reasons.
>>
>> The larger areca card has optional 1G write cache. With the Battery
>> Backup it's not cheap, but then neither is my data
>
> Why is a battery backup for the RAID controller necessary if you have
> a good UPS and automated shutdown facility?

Well, I have seen UPS's fail, and I figure my data is worth a whole  
lot more than the cost of a decent RAID card.

Dave
> -- 
> Regards,
>
> Clifford Ilkay
> Dinamis Corporation
> 3266 Yonge Street, Suite 1419
> Toronto, ON
> Canada  M4N 3P6
>
> +1 416-410-3326
> --
> The Toronto Linux Users Group.      Meetings: http://tlug.ss.org
> TLUG requests: Linux topics, No HTML, wrap text below 80 columns
> How to UNSUBSCRIBE: http://tlug.ss.org/subscribe.shtml
>

--
The Toronto Linux Users Group.      Meetings: http://tlug.ss.org
TLUG requests: Linux topics, No HTML, wrap text below 80 columns
How to UNSUBSCRIBE: http://tlug.ss.org/subscribe.shtml