On Sat, 30 Oct 2004 00:01:43 +0100, Joao Clemente <[EMAIL PROTECTED]> wrote: > Hi. > For the first time I'm gonna setup a server with SCSI disks (until now > I've done it only with IDE - regular ATA or SATA) > > I'm getting a completly new server (P4 3Ghz, Dual-Channel DDR 400, MB > with intel chipset) and, while I have a good ideia on these components, > I would like to setup a RAID-1 system with SCSI disks... > > I'm looking for advice on these: wich scsi controller should I buy? > Software or Hardware RAID-1? Wich disk brand? (I'm getting a couple of > 36GB, it is more than enough space for my setup)
Linux software RAID is usually good enough, but since you already invested a lot in SCSI, go for the hardware RAID. There's a recent thread in this mailing list concerning hardware vs software RAID. There are a lot of good hardware RAID cards to choose from. On a lot of enterprise machines you'd get good ones by default. Linux has quite a good sizeable roster of supported SCSI chipsets. > Which are the tradeoffs of hard vs software raid1? What happens/How do > we proceed if 1 disk fails (how do we know it, how do we replace/resync > them?) The card's custom chip does the computing on hardware raid setups, while software raid taxes the cpu for the computing. Otherwise, it's almost the same. When a disk fails, the other part in the RAID 1 (mirror) setup takes over. It'll be preferrable if you could replace the disk once it fails though - which is why hotplug is really a preferred feature. Do note though that RAID 1 won't help you that much - it's better if you could try higher RAID levels (RAID 5) for data integrity. RAID 1 will only mirror disks - and that would also mean should there be errors in one disk it gets propagated to the mirror as well. > This server can be shutdown for maintenance at off-work hours, so I > don't need any hot-plugging capability.. (this is a controller feature, > right?) Yep. Usually hotpluggability is already built-in in a couple of SCSI RAID cards. The good thing with hotplug is that when one disk fails, you could replace it on the fly. Another thing I haven't tried is to do hotswap on Linux software raid (though I've done hotswap on hardware raid with no problems). > I'm quite confused about all the SCSI variations.. > > This is what I've found so far are somewhat like this: > - SCSI disks, all Ultra320Wide: > Seagate Cheetah 10K 68 pin, 36Gb - 160 EUR > Fujitsu 10K 68 pin, 36Gb - 150 EUR > Fujitsu 10K SCA/80pin, 36Gb - 150 EUR > Fujitsu 15K 68 pin, 18Gb - 185 EUR > Fujitsu 15K SCA/80pin, 18Gb - 185 EUR > Ok, no problem with these... any brand/model suggestions? > - Controllers > Several Adaptec SCSI Cards from 200 to 400 EUR, wich can have: > - 32 or 64bit > - 160MB or Ultra320 > - Raid (or not, when they say nothing.. I think) (the RAID ones start > at 400 EUR and I've seen up to 950 EUR) > > I'm confused... none of the descriptions of the Adaptec controller I've > seen state the connectors (68/80 pins)... now add more controller to the > mess: The PCI bus has two variations - 32bit PCI (the short one found in most PCs), and the 64bit PCI (the longer ones found in servers). There's also PCI-X. You can safely guess that in terms of bus speed it goes this way: 32bit PCI < 64bit PCI < PCI-X. SCSI-2 disks have an 80-pin setup. SCSI-3 disks have a 68-pin setup. SCA in SCSI just integrates the data and power wires to a single attachment (hence Single Connector Attachment) > Tekram PCI DC395UW - 56 EUR > Tekram PCI DC390U2B - 102 EUR > Tekram PCI DC390U2W Ultra 2 Low WIDE SCSI - 126 EUR > Tekram PCI DC390U3W Ultra 3 WIDE SCSI 160 - 182 EUR > Tekram PCI DC390U4W Ultra 4 WIDE SCSI 320 - 223 EUR > > Damn... Really confused... Please confirm these toughs also: > UltraWideSCSI = 68 pin ... What is "2", "3" or "4" ?!? These seem > "similar" to ATA 66/100/133 - the bus speed, is that it? > So, what's SCA? None of these controllers says SCA... Ultra-Wide SCSI = SCSI-3. For the other definitions - see my post above. I think the 2/3/4 has something to do with the data rate. At any rate, to really take advantage of ultra-wide SCSI you'd need to have 64-bit PCI slots or PCI-X slots, as 32-bit PCI would cut down performance sharply. > Any help? > > Ps: I supose getting a SCSI crontroller built-in on the motherboard is > stupid? Those are low-value/performance controllers? Not all of them are low-value/performance connectors. Some are of very good quality. You could always check the chipset used and ascertain from other sources if the chipset is good enough. -- Paolo Alexis Falcone [EMAIL PROTECTED] -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of "unsubscribe". Trouble? Contact [EMAIL PROTECTED]
