On Thu, 2005-06-23 at 09:03 -0400, Guy wrote: > > > -----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. > or build with raid6. but anyway, once u a disk, u will need to have a rsync. with MD, u might try the fr5. no money, otherwise buy one and try. :P i think i need a 4U unit, dual amd64... ming > > > > > > > > Guy > > > > > > > > >
Attachment:
signature.asc
Description: This is a digitally signed message part
