#238429 - 20/10/2004 21:31
Raid systems: Proprietary?
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carpal tunnel
Registered: 20/12/1999
Posts: 31565
Loc: Seattle, WA
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Let's say I've got a RAID0 system (two drives mirrored) plugged into a motherboard's built-in Promise RAID controller.
Let's say the mobo blows a gasket, letting out the expensive Blue Smoke, and won't POST any more.
Now I buy a new mobo, and it's got a different brand of RAID controller, or perhaps none at all and I'm forced to purchase a third-party RAID card which may or may not be a Promise card.
If I plug those drives into the new system, will they work and will their data still be intact? Or is the RAID formatting and information a proprietary standard that varies from controller to controller?
(I'm aware that there's other issues such as the OS having all the wrong mobo drivers installed. Let's assume all I want to do is recover the user-made data before wiping the drives for a new OS.)
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#238430 - 20/10/2004 21:51
Re: Raid systems: Proprietary?
[Re: tfabris]
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carpal tunnel
Registered: 06/10/1999
Posts: 2591
Loc: Seattle, WA, U.S.A.
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Quote:
If I plug those drives into the new system, will they work and will their data still be intact? Or is the RAID formatting and information a proprietary standard that varies from controller to controller?
Generally speaking, B.
_________________________
Jim
'Tis the exceptional fellow who lies awake at night thinking of his successes.
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#238431 - 20/10/2004 21:54
Re: Raid systems: Proprietary?
[Re: tfabris]
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addict
Registered: 11/11/2001
Posts: 552
Loc: Houston, TX
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Quote:
RAID0 system (two drives mirrored)
Er, RAID0 is striped, not mirrored, hence the 0.
And to answer your question, it would be a very very good idea to stick with the same brand and model of RAID card to make sure it works.
_________________________
--Ben
78GB MkIIa, Dead tuner.
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#238432 - 20/10/2004 21:55
Re: Raid systems: Proprietary?
[Re: jimhogan]
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carpal tunnel
Registered: 20/12/1999
Posts: 31565
Loc: Seattle, WA
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Quote:
Generally speaking, B.
Figured. My original guess as to the answer was:
"One's chances of success get exponentially better if the replacement RAID controller is also a Promise controller."
True?
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#238433 - 20/10/2004 21:55
Re: Raid systems: Proprietary?
[Re: BAKup]
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carpal tunnel
Registered: 20/12/1999
Posts: 31565
Loc: Seattle, WA
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Quote:
Er, RAID0 is striped, not mirrored, hence the 0.
Woops, sorry, meant RAID1.
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#238434 - 20/10/2004 22:00
Re: Raid systems: Proprietary?
[Re: tfabris]
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addict
Registered: 11/11/2001
Posts: 552
Loc: Houston, TX
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Quote:
"One's chances of success get exponentially better if the replacement RAID controller is also a Promise controller."
True?
True.
_________________________
--Ben
78GB MkIIa, Dead tuner.
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#238435 - 20/10/2004 22:09
Re: Raid systems: Proprietary?
[Re: tfabris]
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carpal tunnel
Registered: 06/10/1999
Posts: 2591
Loc: Seattle, WA, U.S.A.
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Quote:
Woops, sorry, meant RAID1.
Oh, good. I didn't pick up on the discrepancy when I scanned your post. I was just being Mr. Doom-N-Gloom.
You probably still want to search out an identical controller, but I would say that you stand a better chance of having the controller identify one of the drives as part of a degraded mirror than having that same controller figure out a RAID-0 stripe. Some super-simple RAID devices like Arco write signatures to disk that mean they store less on the controller, but others write most everything back to flash on the controller. Pluuuus with RAID-1, you'd stand some chance of recovering data, I think, even if you couldn't get the controller to ID it.
And here I was thinking you were toast 
_________________________
Jim
'Tis the exceptional fellow who lies awake at night thinking of his successes.
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#238436 - 20/10/2004 22:12
Re: Raid systems: Proprietary?
[Re: jimhogan]
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carpal tunnel
Registered: 20/12/1999
Posts: 31565
Loc: Seattle, WA
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Fortunately, it's not me, it's Tod.
Thanks for the information, everyone, I think it will help him out a lot.
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#238437 - 21/10/2004 00:18
Re: Raid systems: Proprietary?
[Re: tfabris]
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carpal tunnel
Registered: 29/08/2000
Posts: 14477
Loc: Canada
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As others have said, it's a proprietary hack. IF you run Linux, the hack can be undone after a catastrophe, but for MS and other OSs, it'll be SOL.
In the longer term, a new standard for RAID headers is emerging, know as "DDF". But support is patchy at present.
Cheers
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#238438 - 21/10/2004 09:19
Re: Raid systems: Proprietary?
[Re: tfabris]
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carpal tunnel
Registered: 18/06/2001
Posts: 2504
Loc: Roma, Italy
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One advantage of having a OS-based, software RAID system is in fact that you may change hardware completely and the OS will recognise the stripe/mirror set.
Disadvantage is of course performance.
On a small server here I have a W2K-based Raid-5 system with three disks, and I've gone through mobo replacement (changed brand/model) and OS reinstallation and the software based raid-5 set survived.
Of course the OS was on a different, independent disk, since the OS needs to be up and running to detect a raid set, import it and enable it correctly.
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= Taym =
MK2a #040103216 * 100Gb *All/Colors* Radio * 3.0a11 * Hijack = taympeg
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#238439 - 21/10/2004 12:21
Re: Raid systems: Proprietary?
[Re: Taym]
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carpal tunnel
Registered: 29/08/2000
Posts: 14477
Loc: Canada
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Quote:
Disadvantage is of course performance.
Not always -- Of course this will depend upon the quality of the implementation. Linux software RAID routinely trounces hardware RAID solutions -- with soft RAID, the O/S can better schedule and optimize I/O to the physical drives, by having more knowledge of what is happening than a hardware RAID would have.
Cheers
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#238440 - 21/10/2004 14:21
Re: Raid systems: Proprietary?
[Re: mlord]
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carpal tunnel
Registered: 18/06/2001
Posts: 2504
Loc: Roma, Italy
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True!
And supposedly Widnows implementation of raid is good too.
I was actually referring to the performance of the overall system, since the CPU is now in charge of RAID as well as all the rest. On the other hand, I personally never spent time in finding out how much more resources would be devoted to that, and by simply looking at it, the small server I referred to in my previous post does not seem to show any more CPU time devoted to disk management. It's not a heavily used server, though, so I don't know how it would behave under stress...
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= Taym =
MK2a #040103216 * 100Gb *All/Colors* Radio * 3.0a11 * Hijack = taympeg
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#238441 - 21/10/2004 14:55
Re: Raid systems: Proprietary?
[Re: mlord]
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carpal tunnel
Registered: 25/12/2000
Posts: 16706
Loc: Raleigh, NC US
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No to mention that hardware RAID has to go through a single IO channel, while software can take advantage of multiple channels. What we need is a RAID accelerator of some nature to offload the RAID tasks from the CPU.
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Bitt Faulk
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#238442 - 21/10/2004 19:30
Re: Raid systems: Proprietary?
[Re: Taym]
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Carpal Tunnel
Registered: 08/02/2002
Posts: 3411
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Code:
11:42am up 37 days, 1:35, 3 users, load average: 0.10, 0.20, 0.42
161 processes: 160 sleeping, 1 running, 0 zombie, 0 stopped
CPU states: 1.1% user, 4.7% system, 0.0% nice, 94.1% idle
Mem: 387308K av, 378620K used, 8688K free, 117560K shrd, 74840K buff
Swap: 995944K av, 66612K used, 929332K free 92108K cached
PID USER PRI NI SIZE RSS SHARE STAT %CPU %MEM CTIME COMMAND
7208 genixia 16 0 1184 1184 876 R 5.0 0.3 0:01 top
2034 genixia 2 0 2672 2008 1236 S 0.5 0.5 2:42 gnome-terminal
1773 root 3 0 117M 109M 5552 S 0.3 29.0 3420m X
1 root 0 0 132 76 60 S 0.0 0.0 7764m init
2 root 0 0 0 0 0 SW 0.0 0.0 0:42 kflushd
3 root 0 0 0 0 0 SW 0.0 0.0 0:13 kupdate
4 root 0 0 0 0 0 SW 0.0 0.0 0:00 kpiod
5 root 0 0 0 0 0 SW 0.0 0.0 5:50 kswapd
6 root -20 -20 0 0 0 SW< 0.0 0.0 0:00 mdrecoveryd
7 root -20 -20 0 0 0 SW< 0.0 0.0 0:00 raid1d
8 root 19 19 0 0 0 SWN 0.0 0.0 0:08 raid1syncd
9 root -20 -20 0 0 0 SW< 0.0 0.0 0:00 raid1d
10 root 19 19 0 0 0 SWN 0.0 0.0 0:02 raid1syncd
11 root -20 -20 0 0 0 SW< 0.0 0.0 0:00 raid1d
12 root 19 19 0 0 0 SWN 0.0 0.0 0:08 raid1syncd
13 root -20 -20 0 0 0 SW< 0.0 0.0 0:00 raid1d
14 root 19 19 0 0 0 SWN 0.0 0.0 0:19 raid1syncd
15 root -20 -20 0 0 0 SW< 0.0 0.0 0:00 raid1d
16 root 19 19 0 0 0 SWN 0.0 0.0 0:02 raid1syncd
17 root -20 -20 0 0 0 SW< 0.0 0.0 0:00 raid1d
18 root 19 19 0 0 0 SWN 0.0 0.0 2:41 raid1syncd
149 root -20 -20 0 0 0 SW< 0.0 0.0 0:00 raid1d
150 root 19 19 0 0 0 SWN 0.0 0.0 0:00 raid1syncd
7 RAID1 devices, not one of which has used a whole second of CPU time in 37 days of usage. The CTIME for raid1syncd is the time taken reconstructing the arrays after a power failure.
_________________________
Mk2a 60GB Blue. Serial 030102962
sig.mp3: File Format not Valid.
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#238443 - 21/10/2004 19:37
Re: Raid systems: Proprietary?
[Re: genixia]
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carpal tunnel
Registered: 25/12/2000
Posts: 16706
Loc: Raleigh, NC US
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Yeah, well, RAID1 is easy, but all you gain is redundancy (not that that's bad). Higher RAID levels can also improve IO performance, assuming that your RAID controller (be it hardware or software) can keep up, by striping as well. Of course, RAID 0+1 and RAID 10 aren't real difficult either, but they do waste drive space. Of course, most workstation users don't have enough disks to make RAID 5 usable. You, on the other hand, do. You currently are only able to use 50% of your drive space due to mirroring. That could be improved to over 85% with RAID5, even if you leave one drive unused as a hot spare. Yet you haven't. Why? Write performance may be an issue for you, I suppose, which is where RAID5 often loses.
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Bitt Faulk
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#238444 - 21/10/2004 19:45
Re: Raid systems: Proprietary?
[Re: wfaulk]
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Carpal Tunnel
Registered: 08/02/2002
Posts: 3411
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Two drives...many partitions.
You're right though - calculating parity would add significantly to the burden, especially for large writes on a celeron 500. The other factor is that my mobo only has 2 IDE channels so a third disk would have to share a channel which could be nasty. Next upgrade...
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Mk2a 60GB Blue. Serial 030102962
sig.mp3: File Format not Valid.
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#238445 - 21/10/2004 19:50
Re: Raid systems: Proprietary?
[Re: genixia]
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carpal tunnel
Registered: 25/12/2000
Posts: 16706
Loc: Raleigh, NC US
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Quote:
Two drives...many partitions.
Whoops. Bad assumption.
_________________________
Bitt Faulk
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#238446 - 22/10/2004 00:08
Re: Raid systems: Proprietary?
[Re: genixia]
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carpal tunnel
Registered: 29/08/2000
Posts: 14477
Loc: Canada
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Note that the accounting there does not show interrupt handler CPU usage.. which is often the greatest chunk of kernel time spent in a driver.
Cheers
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#238447 - 22/10/2004 14:24
Re: Raid systems: Proprietary?
[Re: tfabris]
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addict
Registered: 13/06/2000
Posts: 429
Loc: Berlin, DE
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Promise cards are known to change raid formating (even for raid1) between revisions of the same model. true story a friend of mine swaped 2 of the same promise cards, and it lost all his data with mirroring.
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80gig red mk2 -- 080000125
(No, I don't actually hate Alan Cox)
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#238449 - 22/10/2004 15:37
Re: Raid systems: Proprietary?
[Re: tfabris]
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carpal tunnel
Registered: 06/10/1999
Posts: 2591
Loc: Seattle, WA, U.S.A.
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Quote:
Crap.
A Promise-related testimonial here that may have some bearing. Like the gent says, I do think Promise says you *should* be able to directly address 1/2 of a broken mirror on a plain IDE channel (maybe with their older FasTracks??) but if not....you can always throw money at it!
_________________________
Jim
'Tis the exceptional fellow who lies awake at night thinking of his successes.
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#238450 - 22/10/2004 15:52
Re: Raid systems: Proprietary?
[Re: jimhogan]
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carpal tunnel
Registered: 20/12/1999
Posts: 31565
Loc: Seattle, WA
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That's good information, thanks!
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#238451 - 03/11/2004 21:07
Re: Raid systems: Proprietary?
[Re: tfabris]
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carpal tunnel
Registered: 20/12/1999
Posts: 31565
Loc: Seattle, WA
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Follow-up. Plugging into the third-party Promise controller did not work, it thinks the drives are empty.
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#238452 - 04/11/2004 19:18
Re: Raid systems: Proprietary?
[Re: SuperQ]
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Pooh-Bah
Registered: 21/07/1999
Posts: 1765
Loc: Brisbane, Queensland, Australi...
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I thought promise cards were also known as 'wing and a prayer' controllers.
speaking of RAID controllers, although i've installed a few, whats the processes for replacing a RAID controller, like adaptec or intel, if the controller fails. Is it just a matter of plugging in the new card and it discovers the RAID configuration automatically? Or does it have to scan the drives?
_________________________
--
Murray
I What part of 'no' don't you understand?
Is it the 'N', or the 'Zero'?
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#238453 - 05/11/2004 01:40
Re: Raid systems: Proprietary?
[Re: genixia]
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addict
Registered: 03/08/1999
Posts: 451
Loc: Canberra, Australia
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Based on this I've recently installed software RAID1 on two 80GB disks on a Fedora Core 3 test 3 server. While I don't have any actual performance statistics, the array seems just as fast as I'd expect it to be, and the RAID1 process has 0 seconds CPU usage in over four days, including several software installs. That and the idea that there's much more chance of getting the RAID array working if we have to change hardware underneath it sold me.
Thanks for the idea, genixia!
Paul
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Owner of Mark I empeg 00061, now better than ever - (Thanks, Rod!) - and Karma 3930000004550
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#238454 - 05/11/2004 01:49
Re: Raid systems: Proprietary?
[Re: PaulWay]
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carpal tunnel
Registered: 25/12/2000
Posts: 16706
Loc: Raleigh, NC US
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Again, ps isn't going to accurately show the CPU usage of the RAID processing because it's all done in the kernel.
_________________________
Bitt Faulk
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#238455 - 05/11/2004 01:49
Re: Raid systems: Proprietary?
[Re: PaulWay]
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carpal tunnel
Registered: 29/08/2000
Posts: 14477
Loc: Canada
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Much of the RAID's CPU usage will be drawn against processes that actually perform the I/O -- such is the nature of a multi-threaded monolithic style OS.
But Linux s/w RAID does indeed outperform nearly(?) all h/w RAID solutions, so it's kinda hard to go wrong by it. Especially if combined with some form of hotswap capable hardware (SATA, Firewire, USB2, etc..).
Cheers
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#238456 - 15/09/2005 16:16
Re: Raid systems: Proprietary?
[Re: mlord]
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Carpal Tunnel
Registered: 08/02/2002
Posts: 3411
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Back from the dead with some recent real-life numbers. 3.2GHz, P4 Xeon, 9 SATA disk array. 3ware HW RAID5: 32Mb/s write, 159Mb/s read  Linux SW RAID5: 112Mb/s write, 138Mb/s read Areca HW RAID5: 113Mb/s write, 365Mb/s read 
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Mk2a 60GB Blue. Serial 030102962
sig.mp3: File Format not Valid.
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#238457 - 15/09/2005 16:43
Re: Raid systems: Proprietary?
[Re: genixia]
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carpal tunnel
Registered: 27/06/1999
Posts: 7058
Loc: Pittsburgh, PA
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#238458 - 15/09/2005 18:34
Re: Raid systems: Proprietary?
[Re: muzza]
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old hand
Registered: 07/01/2005
Posts: 893
Loc: Sector ZZ9pZa
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While you're all talking about RAID...
I am running (er, not for long) an Abit BP6 with 2x Celeron 500's as my fileserver, router, openvpn server and asterisk play machine under Gentoo.
On the hardware setup before this, I had a linux software RAID1 arrangement with a pair of 120GB Seagates on a Promise 20269 Ultra TX2 controller. It was sweet, and never missed a beat.
Now when I moved to the BP6 that I have atm, I thought I'd just use the Highpoint HPT366 that is onboard. It worked a-ok for a while, and last night it just spazzed out on me. The array resynced and the filesystem (reiserfs. why? i don't know) was saying it needed a fsck.
It was like, bleep bleep bleep bleep bleep bleep and then, like, my filesystem wouldn't mount, and I was like, unngh. It devoured my FLACs, and then I had to rip them again...
The PC had been crashing recently, the logs were filling with
Code:
ide: failed opcode was: unknown
hdg: dma_timer_expiry: dma status == 0x21
hdg: DMA timeout error
hdg: dma timeout error: status=0x58 { DriveReady SeekComplete DataRequest }
and
Code:
Sep 13 07:03:10 peaches APIC error on CPU1: 02(02)
Sep 13 07:04:55 peaches APIC error on CPU0: 08(08)
and one drive losing DMA which made resyncing take forever. reiserfsck --rebuild-tree says there is a hardware error.
Basically I'm fed up with this BP6 and its very strange stability (it will be fine for 6 months... and then go crazy... and then miraculously fix itself). Tomorrow it will be replaced with a Abit/VIA/Sempron setup and my old Promise PCI IDE controller.
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