Date: Sun, 30 Mar 2003 18:00:01 +0200 (CEST) From: Lukas Ertl <l.ertl@univie.ac.at> To: Chuck Swiger <cswiger@mac.com> Cc: freebsd-stable@freebsd.org Subject: Re: vinum performance Message-ID: <20030330175605.E23911@leelou.in.tern> In-Reply-To: <3E870CC7.5000204@mac.com> References: <20030330125138.K23911@leelou.in.tern> <3E870CC7.5000204@mac.com>
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On Sun, 30 Mar 2003, Chuck Swiger wrote: > Lukas Ertl wrote: > [ ... ] > > I created several RAID 0 and RAID 5 volumes with different stripe sizes > > and let bonnie++ run over the filesystems. I was quite disappointed abo= ut > > the RAID 5 performance, and even the RAID 0 performance wasn't too good > > (a plain single disk filesystem was almost as fast as or even faster th= an > > a RAID 0 stripe, and I wouldn't expect that). > > > > RAID 5 performance was really a mess, some of the test took more than > > 30min. to complete. > > There are three goals or priorities to choose from when configuring > RAID: performance, reliability, and cost. What are yours? I just wanted to test the performance of these drives and of vinum; I had no goals to reach. > Also, what tasks you intend to use the RAID filesystem for are critical > to consider, even if the answer is simply "undifferentiated > general-purpose storage". In particular, RAID-5 write performance is > going to be slow, even with RAID hardware support which offloads the > parity calculations from the system CPU(s). RAID-5 is best suited for > read-mostly or read-only volumes, where you value cost more than > performance. Ok. But I still don't understand why RAID 5 write performance is _so_ bad. The CPU is not the bottle neck, it's rather bored. And I don't understand why RAID 0 doesn't give a big boost at all. Is the ahc driver known to be slow? > Um, that is a dual-channel card, and you're splitting drives onto both > channels, right? Yes, it is dual channel, but the disks I'm testing are all connected to the same channel. Bad layout? regards, le --=20 Lukas Ertl eMail: l.ertl@univie.ac.at UNIX-Systemadministrator Tel.: (+43 1) 4277-14073 Zentraler Informatikdienst (ZID) Fax.: (+43 1) 4277-9140 der Universit=E4t Wien http://mailbox.univie.ac.at/~le/
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