From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bill Davidsen Subject: Re: Linux SW RAID: HW Raid Controller/JBOD vs. Multiple PCI-e Cards? Date: Sat, 05 May 2007 12:44:47 -0400 Message-ID: <463CB47F.4040206@tmr.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-raid-owner@vger.kernel.org To: Justin Piszcz Cc: linux-raid@vger.kernel.org, xfs@oss.sgi.com List-Id: linux-raid.ids Justin Piszcz wrote: > Question, > > I currently have a 965 chipset-based motherboard, use 4 port onboard > and several PCI-e x1 controller cards for a raid 5 of 10 raptor > drives. I get pretty decent speeds: > > user@host$ time dd if=/dev/zero of=100gb bs=1M count=102400 > 102400+0 records in > 102400+0 records out > 107374182400 bytes (107 GB) copied, 247.134 seconds, 434 MB/s > > real 4m7.164s > user 0m0.223s > sys 3m3.505s > user@host$ time dd if=100gb of=/dev/null bs=1M count=102400 > 102400+0 records in > 102400+0 records out > 107374182400 bytes (107 GB) copied, 172.588 seconds, 622 MB/s > > real 2m52.631s > user 0m0.212s > sys 1m50.905s > user@host$ > > Also, when I run simultaenous dd's from all of the drives, I see > 850-860MB/s, I am curious if there is some kind of limitation with > software raid as to why I am not getting better than 500MB/s for > sequential write speed? With 7 disks, I got about the same speed, > adding 3 more for a total of 10 did not seem to help in regards to > write. However, read improved to 622MBs/ from about 420-430MB/s. > > However, if I want to upgrade to more than 12 disks, I am out of PCI-e > slots, so I was wondering, does anyone on this list run a 16 port > Areca or 3ware card and use it for JBOD? What kind of performance do > you see when using mdadm with such a card? Or if anyone uses mdadm > with less than a 16 port card, I'd like to hear what kind of > experiences you have seen with that type of configuration. RAID5 is not the fastest at write, there are patches being tested to improve that. -- bill davidsen CTO TMR Associates, Inc Doing interesting things with small computers since 1979