> -----Original Message----- > From: Ming Zhang [mailto:mingz@xxxxxxxxxxx] > Sent: Thursday, June 23, 2005 8:32 AM > To: Guy > Cc: bdameron@xxxxxxxxxxxxx; linux-raid@xxxxxxxxxxxxxxx > Subject: RE: More tales of horror from the linux (HW) raid crypt > > On Wed, 2005-06-22 at 23:05 -0400, Guy wrote: > > > -----Original Message----- > > > > > > > > > will this 24 port card itself will be a bottleneck? > > > > > > > > > > ming > > > > > > > > Since the card is PCI-X the only bottleneck on it might be the > Processor > > > since > > > > it is shared with all 24 ports. But I do not know for sure without > > > testing it. > > > > I personally am going to stick with the new 16 port version. Which > is a > > > PCI- > > > > Express card and has twice the CPU power. Since there are so many > > > spindles it > > > > should be pretty darn fast. And remember that even tho the drives > are > > > 150MBps > > > > they realistically only do about 25-30MBps. > > > > > > the problem here is taht each HD can stably deliver 25-30MBps while > the > > > PCI-x will not arrive that high if have 16 or 24 ports. i do not have > a > > > chance to try out though. those bus at most arrive 70-80% the claimed > > > peak # :P > > > > Maybe my math is wrong... > > But 24 disks at 30 MB/s is 720 MB/s, that is about 68.2% of the PCI-X > > bandwidth of 1056 MB/s. > yes, u math is better. > > > > > Also, 30 MB/s assumes sequential disk access. That does not occur in > the > > real world. Only during testing. IMO > yes, only during test. but what if people build raid5 base on it, this > is probably what people do. and then a disk fail? then a full disk > sequential access becomes normal. and disk fail in 24 disk is not so > uncommon. But, this is hardware RAID. A re-sync would not affect the PCI bus. All disk i/o related to re-building the array would be internal to the card. However, even if it were a software RAID card, the PCI-X would be at 68.2% load, so it should not be a problem. If my math is correct! :) Also, a single RAID5 array on 24 disks would be high risk of a double failure. I think I would build 2 RAID5 arrays of 12 disks each. Or 2 RAID5 arrays of 11 disks each, with 2 spares. > > > > > Guy > > > > > - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
