2850 drive bays not hot-swap?

[William Warren]

I can see your points.  When i provision a server i bypass the dell 
controllers and use 3ware.  Since md is faster for you there's no reason 
to use the dell controller..<G>


Brett Dikeman wrote:
> On Jan 24, 2008 3:35 PM, William Warren
> <hescominsoon at emmanuelcomputerconsulting.com> wrote:
>> i'm curious why you aren't using the raid card?
> 
> Simplicity, familiarity, standardization, and better OS integration
> and monitoring.
> 
> Sure, I lose the battery-backed write cache some cards have, and I
> lose is the continuous verify the Dell controllers perform.  If you
> want to come close to the latter functionality with linux md, you can
> do it quite easily by setting a very low minimum rebuild rate and
> regularly kicking off a verify via cron.
> 
> Performance is fine with linux md (I'm using RAID1 and 10, didn't
> think to benchmark RAID5), and interestingly enough- Solaris ZFS
> RAID-Z across 5 drives was around 185 MB/sec whereas the PERC
> controller with 4 drives in RAID0 ran out of steam around the 100
> MB/sec mark.
> 
> hdparm's timed buffered disk reads on the md devices yield 100 MB/sec
> for the 4-drive RAID10 array, and the RAID1 array clocks in at 73
> MB/sec.  Write on the RAID10 with dd (from /dev/zero to a 50% full xfs
> filesystem with 900,000 files, mounted
> rw,noatime,nodiratime,logbufs=8) yields about 78 MB/sec; a dd read (to
> /dev/null) is 148 MB/sec.  Bonnie++ on the RAID10 yielded 77.5 MB/sec
> write, 119 MB/sec read.
> 
>>  Hotswap under linux software raid isn't totally automatic IIRC.
> 
> Certainly, but I don't need pop-a-drive-in-and-done automatic
> rebuilds.  What I do need, however, is to be able to swap the drive
> out, repartition the new one, and add it back into the array without
> rebooting, especially since this machine takes something like 5+
> minutes to boot.  That's 1/6th the time it takes to rebuild my system
> mirror :-)
> 
>>  here's a link from the archives HTH.
>> http://lists.us.dell.com/pipermail/linux-poweredge/2003-July/008898.html
> 
> Ah!  Very nice, those /proc pokes were exactly what I was looking for;
> thank you! (haven't tried it yet, but I will.)  That email also
> reminded me that I forgot to set up the bootloader on the second
> drive; I did remember /boot (and everything else lives in LVM on top
> of the RAID device.)
> 
> Brett
> 

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