SCSI vs SATA considerations
I'm in the middle of some implementation decisions.
I've been used to scsi, and now have had some experience with sata.
I was never able to fully utilize scsi due do insufficient cpu/FSB speeds.
A 29160 with Atlas 10K3 on a FSB 112, 550MHz cpu, hdparm -t gets me 27MB/s.
On a new DDR400, 2200MHz cpu, system, using 29160 with an IBM DDYS disk, I get 37MB/s. For reasons I don't understand, the DDYS won't negotiate at 80MB/s, will only do 40MB/s.
The problem here is that I simply don't know what performance I can expect from the Atlas 10K3, if I move it to this new system.
After resolving the system lockup problem using Seagate 7200.7 160GB sata with Sil3121a and nForce2 Ultra400, hdparm -t gets me 54-55MB/s.
(For those interested, it's not a Seagate problem, but an nForce2 APIC problem, which can be solved with
http://www.kernel.org/pub/linux/kernel/people/bart/2.6.0-test11-bart1/broken-out/nforce2-disconnect-quirk.patch
. The patch doesn't apply cleanly to 2.6.5, so I added it manually to fixes.c . I can make a diff if needed..)
I'd prefer using both scsi and sata, for reasons of both performance and for having experience with both technologies.
The system will be used with vmware, using Linux as the host system. If I go for the combined scsi/sata solution, I expect using scsi for the host OS, vmware layer and the virtual client systems: XP, W2K, two more Linux distros, and use sata for storage, i.e. /home and what else..
Using vmware, I can expect some swapping going on, though I have 1GB ram.
Therefore, using two disks, it makes sense setting up swap on both disks with PRI= for raid-like swapping. However, I fail to foresee how this is expected to perform with two different disk subsystems with different characteristics and speeds, especially as I don't know how well the Atlas disk will perform on the new, faster system.
Alternatively, I could go for using two Seagate sata disks, and no scsi.
Anyone care to shed a light on the swap issues?
I'd also like a comment on the IBM DDYS negotiating at only 40MB/s.
Signature · 5 lines
Kind regards, Mogens Valentin Networking, Security www.danbbs.dk/~monz Phone +45 32 525 878
Quoted 3 lines · Mogens Valentin
On a new DDR400, 2200MHz cpu, system, using 29160 with an IBM DDYS disk, I get 37MB/s. For reasons I don't understand, the DDYS won't negotiate at 80MB/s, will only do 40MB/s.
Negotiation problems are normally cable or termination issues.
Signature · 6 lines
"Next the statesmen will invent cheap lies, putting the blame upon the nation that is attacked, and every man will be glad of those conscience-soothing falsities, and will diligently study them, and refuse to examine any refutations of them; and thus he will by and by convince himself that the war is just, and will thank God for the better sleep he enjoys after this process of grotesque self-deception." -- Mark Twain