HPT370 RAID-1 or Software RAID-1, what's "best"?
Hi,
Quoted 3 lines · Luigi Genoni
HPT370 IDE Raid is not really an hardware raid.
It is a software Raid, since Linux does not use tha raid implementation that comes with the BIOS, but it uses softwareraid.
That doesn't prevent me from saying that real hardware raid might be better. But is the thing you wish to say that there's no difference, or what?
Quoted 3 lines · Alan Cox
The raid rebuild time is identical for pretty much any set up. With the softraid its intentionally defaulting to a low fraction of I/O bandwidth so it doesnt disrupt normal operation.
I experienced it took at about twice the time for a rebuild. I don't exactly remember the test results, and they aren't available to me until Monday. If you're interested...
Maybe things have changed a lot since last year, when I did the tests.
Quoted 1 line
Also as far is his question goes - both are software raid
See above.
Thunder
Signature · 13 lines
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Quoted 1 line
uudecode $file | perl
Quoted 4 lines
Quoted 1 line
that comes with the BIOS, but it uses softwareraid.
That doesn't prevent me from saying that real hardware raid might be better. But is the thing you wish to say that there's no difference, or what?
The CPU can saturate the I/O bandwidth (if not then go upgrade to a pentium) At that point its totally disk I/O bound so there will be no difference
Quoted 9 lines · Thunder from the hill
Hi,
Quoted 3 lines · Luigi Genoni
HPT370 IDE Raid is not really an hardware raid.
It is a software Raid, since Linux does not use tha raid implementation that comes with the BIOS, but it uses softwareraid.That doesn't prevent me from saying that real hardware raid might be better. But is the thing you wish to say that there's no difference, or what?
Hardware RAID is indeed better, but what you get using HPT370 IDE controlelr is not hardware raid at all. Just read the code of the driver. You get a software raid, period.
Quoted 35 lines
Quoted 3 lines · Alan Cox
The raid rebuild time is identical for pretty much any set up. With the softraid its intentionally defaulting to a low fraction of I/O bandwidth so it doesnt disrupt normal operation.
I experienced it took at about twice the time for a rebuild. I don't exactly remember the test results, and they aren't available to me until Monday. If you're interested...
Maybe things have changed a lot since last year, when I did the tests.Quoted 1 line
Also as far is his question goes - both are software raid
See above.
Thunder
--
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====
Extract this and see what will happen if you execute my signature. Just save it to file and do aQuoted 1 line
uudecode $file | perl
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Quoted 3 lines
Hardware RAID is indeed better, but what you get using HPT370 IDE controlelr is not hardware raid at all. Just read the code of the driver. You get a software raid, period.
Its not always that simple either.
Software raid on aic7xxx totally blows away the Dell/AMI megaraid card I have, to the point the megaraid now resides in my testing bucket. The promise Supertrak 100 (now superceded by the SX6000) is also slower than the software IDE raid, but does use less CPU in RAID5 mode.
Some hardware raid cards do seem to be winners. The Dell Perc2/QC aacraid based boards (233Mhz ARM etc) really shift. When I've had the chance to borrow the disks to test I've seen it running over 100Mbytes/second. It also supports nice stuff like online reconfiguration of active volumes. [$$stupid from Dell $$notalot from ebay ;)]
Alan
Quoted 10 lines · Alan Cox
Quoted 3 lines
Hardware RAID is indeed better, but what you get using HPT370 IDE controlelr is not hardware raid at all. Just read the code of the driver. You get a software raid, period.
Its not always that simple either.
Software raid on aic7xxx totally blows away the Dell/AMI megaraid card I have, to the point the megaraid now resides in my testing bucket. The promise Supertrak 100 (now superceded by the SX6000) is also slower than the software IDE raid, but does use less CPU in RAID5 mode.
yes, I know, but I was talking "generaliter"
Quoted 6 lines
Some hardware raid cards do seem to be winners. The Dell Perc2/QC aacraid based boards (233Mhz ARM etc) really shift. When I've had the chance to borrow the disks to test I've seen it running over 100Mbytes/second. It also supports nice stuff like online reconfiguration of active volumes. [$$stupid from Dell $$notalot from ebay ;)]
On my CISS Compaq array I get quite similar performances ;)
Luigi
Quoted 11 lines · Alan Cox
Quoted 3 lines
Hardware RAID is indeed better, but what you get using HPT370 IDE controlelr is not hardware raid at all. Just read the code of the driver. You get a software raid, period.
Its not always that simple either.
Software raid on aic7xxx totally blows away the Dell/AMI megaraid card I have, to the point the megaraid now resides in my testing bucket. The promise Supertrak 100 (now superceded by the SX6000) is also slower than the software IDE raid, but does use less CPU in RAID5 mode.
Quoted 5 lines
Some hardware raid cards do seem to be winners. The Dell Perc2/QC aacraid based boards (233Mhz ARM etc) really shift. When I've had the chance to borrow the disks to test I've seen it running over 100Mbytes/second. It also supports nice stuff like online reconfiguration of active volumes. [$$stupid from Dell $$notalot from ebay ;)]
Another issue is that not all RAID hardware supports anything below the
drive level, while kernel RAID runs at the partition level, and allows various things to be in partitions on drives, rather than using the whole drive for one thing.
I have done things like have four drives split into RAID-5 using one set
of partitions, and RAID-0+1 on another, using different stripe sizes for the two md sets. And I got there after a lot of trying configs, it reall worked best that way. Putting overflow swap space on drives with RAID allows some protection against running out of memory, although you don't usually want your main swap fighing for space on the elevator.
There probably is a RAID controller which can do this just as well, but
I haven't used it. Versatility is the name of the game for kernel RAID.
Signature · 3 lines
bill davidsen <[email protected]> CTO, TMR Associates, Inc Doing interesting things with little computers since 1979.
Quoted 11 lines · Alan Cox
Quoted 3 lines
Hardware RAID is indeed better, but what you get using HPT370 IDE controlelr is not hardware raid at all. Just read the code of the driver. You get a software raid, period.
Its not always that simple either.
Software raid on aic7xxx totally blows away the Dell/AMI megaraid card I have, to the point the megaraid now resides in my testing bucket. The promise Supertrak 100 (now superceded by the SX6000) is also slower than the software IDE raid, but does use less CPU in RAID5 mode.
Quoted 5 lines
Some hardware raid cards do seem to be winners. The Dell Perc2/QC aacraid based boards (233Mhz ARM etc) really shift. When I've had the chance to borrow the disks to test I've seen it running over 100Mbytes/second. It also supports nice stuff like online reconfiguration of active volumes. [$$stupid from Dell $$notalot from ebay ;)]
Yep, but the aacraid controllers based on i960 don't do so well. I was able to double my throughput after switching to software raid (it acts like an aic7xxx in scsi mode, even using the adaptec driver instead of aacraid).
Mike