[NTLUG:Discuss] Re: looking for raid & controller advice -- ? FRAID" card = "software RAID"

[Bryan J. Smith]

I wrote the 2004 April article for a reason.
There are at least 4 major approaches to ATA RAID.
Unfortunately the article is not on-line.

-- 
Bryan J. Smith (currently mobile)
b.j.smith at ieee.org

-----Original Message-----
From:  Kevin Brannen 
Date:  04-12-4 15:07
To:  NTLUG Discussion List 
Subj:  Re: [NTLUG:Discuss]  Re: looking for raid & controller advice -- "FRAID" card =	"software RAID"

Bryan,

Thanks for all the info!  I almost got lost in it, but managed to hang 
on. :-)

For those who like fun thought questions, feel free to jump straight to 
the bottom and reply. :-)  But for those who want to enjoy the journey...

Bryan J. Smith wrote:

>[ FYI, there is a further discussion of this in the 2004 April article
>of Sys Admin magazine entitled "Dissecting ATA RAID Options." ]
>
>On Sat, 2004-12-04 at 02:54, Kevin Brannen wrote:
>  
>
>>I need to build a file server for my church.  Rudundancy is a must, 
>>since I've lost several drives in the recent past (I'm not too keen on 
>>the WD2000 right now--I might even have some used ones to sell soon).  
>>I'm thinking a cheap way to solve this (as opposed to buying a NAS 
>>solution) is to get a semi-low cost computer, add 1G of RAM for lots of 
>>cache, and stick a 3ware 7506-4LP in it with 3 250G EIDE drives in a 
>>RAID-5 config,
>>    
>>
>
>Why not 4 drives for the same storage in RAID-0+1?
>It will be much, much faster.
>  
>

Because speed is not the issue or the goal.  Sorry, I really should have 
mentioned that!  The file server I'd build only has to serve 2 
computers, over the Gb ethernet card as I mentioned.  So the NIC will be 
the bottleneck.  Nevertheless, my goal is data safety and capacity.  The 
2 client machine control CD duplicators, but even burning at 48X 
shouldn't tax the file server.  Presently, when the 2 clients talk to 
each other, they can transfer a 500MB image to the other in about 20s.  
Since it takes almost 3 minutes to burn a full CD, you can see that 
speed is not an issue -- even if both are going at once.  They will be 
consistently serving large files (500MB+), so read cache won't matter; 
write cache may not either when you consider 500MB files, though they 
will be doing reading much more than writing.

If I were to go with 0+1, which I don't think I need, I'd have to get 
the -8 version of the card, because I want to be able to approach TB 
capacity over the next couple of years.  I've got almost 200GB now and 
am growing faster than planned, so I am concerned about size.

Because of the reliability concerns, I'm thinking hard about doing 
RAID-5 with a hot-spare; which seems wasteful to me initially, until I 
remember that I've just lost 2 drives in the last week, and now will 
have to spend a day or more reloading images from old CDs.  Grrr!

>running Linux and serving the files out the Gb network 
>port with a Samba server.  (Yes, the 2 clients are Win2k, ugh!)  So far 
>so good.  I can get all the parts new, including a spare 4th drive for 
>$1500, maybe somewhat less.
>...
>
>Only the 9500S series now leverages _both_ SRAM + DRAM for the
>_ultimate_ performance _regardless_ of RAID level.  But you'll pay for
>it.
>
>In a nutshell, _no_ sub-$500 RAID-5 uC+DRAM controller I've seen can
>match 3Ware 7000/8000 at RAID-0+1 in write performance.  With the cost
>of ATA drives being so low, it's much more price/performance effective
>to go RAID-0+1 IMHO.  Unless you are talking 8+ drives.
>  
>

OK, let's ignore 0+1 for a minute and discuss RAID-5. :-)

A 7506-8 is in $390 area, a 9500S-8 is in the $440 area (both sub $500 
cards BTW :-).  Is the 9500S worth the extra $50?  If yes, that's 
probably $50 well spent and within my budget.  Your thoughts?

Also, if I were to go with the 9500S-8, I only see SATA versions.  I 
haven't heard any good SATA success stories on Linux yet.  Not on any 
newsgroups, from friends, anywhere.  (maybe that means I don't read 
enough :-)  Does the 9500S deal with that and just present an interface 
to the Linux kernel so I shouldn't care?  But that is why I've been 
focusing on EIDE controllers.

>>* It advertises Linux support,
>>    
>>
>
>3Ware has had a _stock_ kernel support since 2.2.15 (yes, that's _2.2_,
>not 2.4).
>
>...
>  
>
Execellent!

>>and software called Disk Manager.  Does DM work under Linux?
>>    
>>
>
>Yes, there is a specific version for Linux, along with a CLI (command
>line interface) version (the two are mutually exlusive).  The regular
>(non-CLI) DM appears as a web server, and you can then pull up a web
>browser to it.  It only allows local access as root by default.
>
>...more good stuff...
>  
>
Cool!

>>Is it useful?  Or do you just tell the card via a BIOS like tool to go
>>RAID-5 and the card handles it all automatically and Linux sees the
>>card as 1 big drive.
>>    
>>
>
>_Both_.  _All_ "intelligent" RAID cards have _both_ a BIOS _and_ an
>on-board intelligence.  That's how they differ from the "FRAID" cards.
>
>...
>
Hmm, OK, but I think I definitely need someone to help me on the SATA 
question above. :-)

>>* Will this card demand to be the "first drive"?
>>    
>>
>