On Sat, 2005-07-09 at 20:52 +0200, Farkas Levente wrote:
we use this since about 3 years. that day we read all kinf of docs and most people suggest to use in this way.
I know they do. I just don't agree with it.
faster (even you don't think so),
Oh, it probably is faster with software, because the Linux kernel will buffer up writes far better than the small SRAM cache of the 3Ware Escalade 8506 (only 2MB in the -8, 4MB in the -12).
The lack of DRAM buffer is why 3Ware introduced the Escalade 9500S series -- now you get both several MBs of 0 wait state SRAM for the switching ASIC with a good amount of DRAM buffer for RAID-5.
easier,
Actually, I very much disagree with that assertion. What's easier than leaving everything -- build to failover to rebuild than to the on-board, intelligent ASIC? GPL drivers in the stock kernel since 2.2.15 (yes, that's _2.2_).
I'm not making this up, I have _numerous_ 3Ware Escalade 7000 series cards that I have been deployed since Red Hat Linux 6.x / kernel 2.2.x and have been upgraded through kernel 2.6 and I have changed _zilch_ except for maybe 1-2 firmware upgrades. Dealing with LVM and MD changes over the same period have been far more difficult.
I've also moved probably a dozen volumes from 6000 series to 7000 series in my time, and even one volume set from 8000 series to 9000 series more recently (although I have been avoiding the 9000 series because of others with reported issues -- typical of a new 3Ware series).
safer.
Again, totally disagree with that assertion. I'd rather leave RAID to a fairly static and proven firmware and driver in an intelligent, massively queuing design, which makes the OS/software merely a dumb block device that is hard to "screw up." ;->
Not to trample on your issues and kick you when you are down, but didn't you just have a problem? ;->
The _only_ RAID-5 issue I have _ever_ had with 3Ware was when they added it to the Escalade 6000 series. 3Ware quickly realized there was a design consideration in the 6000 that took issue with the RAID-5 algorithm, which prompted the 7000 series design (which is also used in the 8000 and 9000 too).
just look trough the linux-raid list.
Well, there's several things:
1. A lot of people throw all ATA RAID solutions into the same bucket, and don't recognize the difference with 3Ware.
2. Even those that do recognize 3Ware does use an on-board ASIC intelligence don't realize how well it queues and transfers blocks efficiently compared to traditional, "yesteryear" i960 designs in the Promise SuperTrak and Adaptec 2400A/2800A.
3. Some arguments I've heard say "well, I don't want the volume to be tied to the card" when 3Ware volumes are directly movable to newer card versions.
Yes, 3Ware cards (prior to the 9000 series) "suck" at RAID-5 writes, because the use a small amount of costly (transistor-wise) SRAM. But using SRAM also means it doesn't need battery backup either.
we always use the latest:-)
Just wondering why you're buying 3Ware cards when you're not using the hardware ASIC at all.
You'd be better off buying RAIDCore cards for the ATA channels if you're going to use LVM/MD for all RAID functionality.
The only time I use LVM with 3Ware is when I'm RAID-0 striping across two cards/volumes (on two separate PCI[-X] channels).