Thread: Re: best arrangement of 3 disks for (insert) performance - Dell
The Dell PERC controllers have a very strong reputation for terrible performance. If you search the archives of the Dell Linux Power Edge list (dell.com/linux), you will find many, many people who get better performance from software RAID, rather than the hw RAID on the PERC. Having said that, the 3/SC might be one of the better PERC controllers. I would spend and hour or two and benchmark hw vs. sw before I committed to either one. Thom Dyson Director of Information Services Sybex, Inc. On 9/12/2003 9:55:40 AM, Richard Jones <rj@last.fm> wrote: > The machine is coming from dell, and i have the option of a > PERC 3/SC RAID Controller (32MB) > or software raid. > > does anyone have any experience of this controller? > its an additional £345 for this controller, i'd be interested to know what > people think - my other option is to buy the raid controller separately, > which appeals to me but i wouldnt know what to look for in a raid > controller. > > that raid controller review site sounds like a good idea :) > > Richard.
I would like to point out though on the PERC controllers that are LSI based ( Megaraid ) there -are- settings that can be changed to fix any o the performance issues. Check the linux megaraid driver list archives to see the full description. I've seen it come up many times and basically all the problems have turned up resolved. Will On Fri, 2003-09-12 at 10:03, Thom Dyson wrote: > > The Dell PERC controllers have a very strong reputation for terrible > performance. If you search the archives of the Dell Linux Power Edge list > (dell.com/linux), you will find many, many people who get better > performance from software RAID, rather than the hw RAID on the PERC. > Having said that, the 3/SC might be one of the better PERC controllers. I > would spend and hour or two and benchmark hw vs. sw before I committed to > either one. > > Thom Dyson > Director of Information Services > Sybex, Inc. > > On 9/12/2003 9:55:40 AM, Richard Jones <rj@last.fm> wrote: > > The machine is coming from dell, and i have the option of a > > PERC 3/SC RAID Controller (32MB) > > or software raid. > > > > does anyone have any experience of this controller? > > its an additional £345 for this controller, i'd be interested to know > what > > people think - my other option is to buy the raid controller separately, > > which appeals to me but i wouldnt know what to look for in a raid > > controller. > > > > that raid controller review site sounds like a good idea :) > > > > Richard. > > > > ---------------------------(end of broadcast)--------------------------- > TIP 4: Don't 'kill -9' the postmaster
Attachment
>>>>> "TD" == Thom Dyson <TDyson@sybex.com> writes: TD> The Dell PERC controllers have a very strong reputation for terrible TD> performance. If you search the archives of the Dell Linux Power Edge list TD> (dell.com/linux), you will find many, many people who get better TD> performance from software RAID, rather than the hw RAID on the PERC. The PERC controllers are just a fancy name for a whole host of different hardware. I have several, and some are made by LSI and some are made by Adaptec. My latest is PERC3/DC which is an LSI MegaRAID and is pretty darned fast. -- =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= Vivek Khera, Ph.D. Khera Communications, Inc. Internet: khera@kciLink.com Rockville, MD +1-240-453-8497 AIM: vivekkhera Y!: vivek_khera http://www.khera.org/~vivek/
>>>>> "WL" == Will LaShell <will@lashell.net> writes: WL> o the performance issues. Check the linux megaraid driver list archives WL> to see the full description. I've seen it come up many times and WL> basically all the problems have turned up resolved. I've seen this advice a couple of times, but perhaps I'm just not a good archive searcher because I can't find such recommendations on the linux-megaraid-devel list archives... Anyone have a direct pointer to right info? -- =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= Vivek Khera, Ph.D. Khera Communications, Inc. Internet: khera@kciLink.com Rockville, MD +1-240-453-8497 AIM: vivekkhera Y!: vivek_khera http://www.khera.org/~vivek/
TDyson@sybex.com ("Thom Dyson") writes:
> The Dell PERC controllers have a very strong reputation for terrible
> performance. If you search the archives of the Dell Linux Power
> Edge list (dell.com/linux), you will find many, many people who get
> better performance from software RAID, rather than the hw RAID on
> the PERC. Having said that, the 3/SC might be one of the better
> PERC controllers. I would spend and hour or two and benchmark hw
> vs. sw before I committed to either one.
I can't agree with that.
1. If you search the archives for messages dated a couple of years
ago, you can find lots of messages indicating terrible performance.
Drivers are not cast in concrete; there has been a LOT of change to
them since then.
2. The second MAJOR merit to hardware RAID is the ability to hot-swap
drives. Software RAID doesn't help with that at all.
3. The _immense_ performance improvement that can be gotten out of
these controllers comes from having fsync() turn into a near no-op
since changes can be committed to the 128K battery-backed cache REALLY
QUICKLY.
That is something you should avoid doing with software RAID in any
case where you actually care about your data.
That third part is where Big Wins come. It is the very same sort of
"big win from cacheing" that we saw, years ago, when we improved
system performance _immensely_ by adding a mere 16 bytes of cache by
buying serial controller cards with cacheing UUARTs. It is akin to
the way SCSI controllers got pretty big performance improvements by
adding 256 bytes of tagged command cache.
--
output = ("cbbrowne" "@" "libertyrms.info")
<http://dev6.int.libertyrms.com/>
Christopher Browne
(416) 646 3304 x124 (land)