Greg Freemyer wrote:
On Wed, Apr 2, 2008 at 5:26 PM, Sam Clemens
wrote: John Bown wrote:
Hello everyone. I have an old server with an IDE RAID card in it on which I'd like to install openSUSE 10.3. The problem is, support for said RAID card (a Dell CERC ATA/100) has been discontinued for some time now. With that I ask, how feasible and/or advisable would it be to attempt the following?
1) Install openSUSE and configure it to use software RAID (two mirrored IDE drives (master/slave) for system, two stripped IDE drives (master/slave) for data) 2) Enable Encrypted File System (EFS)
Basically, I'm worried that an IDE based machine will be painfully slow due to the high disk activity. Ideally I would use the machine's existing SCSI U320 interface, but the required hard drives are just too expensive.
Get some modern SATA disks. They're doing I/O at 300 Gbyte/s now. While they don't have out-of-order queueing like SCSI and SAS, they do offer high burst speeds for I/O (Serial Attached SCSI...same cables but use SAS cards -- which conveniently can ALSO control SATA disks, too. Each port individually determines if that cable is attached to a SATA or an SAS disk.
A few misconceptions there:
1) At least for now a single drive does not have the ability to saturate a 150 Gbyte/sec connection. You only need 300 MB/sec if your using PMP to multiplex multiple drives on one cable. And then you need to be using PCI express because PCI is also too slow to effectively use 300 MB/sec.
I'm not saying that he needs it...only that it's available.
2) SATA-2 drives do now support out of order queueing (NCQ or TCQ, I've forgotten). But the benchmarks are showing that the Linux Kernel elevators work so well that little (or nothing) is gained from letting the drive empty cache out of order. Apparently there are some specific workloads where NCQ is a win.
3) Strangely, most drives do tie 300 MB/sec to the Sata-2 functions set, so if you use the 150 MB/sec throttle jumper to slow down the drive, you loose the NCQ function.
Why deliberately throttle down a drive? They're slow enough already. And the SAS/SATA negotiation standard specifies that the controller and the disk are supposed to negotiate their speed.
4) Ignoring SAS for a second: I assume the old MB under discussion does not have any PCIe slots, so I don't think you will find a sata-2 controller for PCI, so I think you are stuck with Sata-1 functionality and 150MB/sec speed. I don't know about SAS controllers. I have not researched them.
Go to Adaptec's site. There's a lot of whitepapers on the subject...and here's a cool presentation by HP on PHY and signal layer: www.scsita.org/aboutscsi/sas/tutorials/SAS_Phy_layer.pdf -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org For additional commands, e-mail: opensuse+help@opensuse.org