I need your opinion on Linux software RAID. I mean its performace (in
terms of drive read/write time). I've configured Software RAID on two
SATA drives. I figured out the onboard SATA raid controller that this
server has is a fakeraid controller (Works only with the manufacturer
drivers on M$ Windoze). So, resorted to Linux software RAID. I've had
bad experience in the past with software RAID with 2.4 kernel based
Linux server. So, I'd like to know if anyone here has experiences with
software RAID on 2.6 kernel (default FC3 kernel).

And by accident, I created three RAID devices (namely md0, md1 and md2
for /boot, / and swap respectively). Do I need to create RAID for swap
parition. Now, I'm worried that it's going to affect the performance. As
I write, it's still going thru FC3 installation process. Probably, I'd
perform some harddrive read/write access tests after installation. I'd
really appreciate if you can share your opinions and experiences with
software RAID in Linux 2.6 kernel (to be specific 2.6.9-smp).

Thanks,
Sanjay.


I've been running software raid5 on / (with 3 ide drives, not SATA), for many months now with no problems whatsoever.  In fact, I moved the array to a new machine and rearranged the drives onto different controllers without a hiccup.

Swap on raid is probably recommended (if the swap device croaks while the system is using it bad things can happen).  But, you are more than welcome to add the partitions in fstab and the kernel will stripe to all of them automatically, so no, raid is not required.

Your raid1 (you didn't make raid0, did you?) device will probably be slightly slower than a single disk for reads, while a bit slower still for writes.  I've done some benchmarking of several software and one hardware raid systems, with less than amazing results.

Please forgive the HTML below-- here is a table of some benchmarked systems.  The fastest machine was Hardware Raid, but it also had 4 disks and much beefier hardware than most of the others.  It's hard to tell-- I'm mostly interested in block read/write, so I ommited other results to save space here.

Tables



Sequential Output (writing to disk) Sequential Input (reading from disk)











Per Chr block rewrite Per Chr Block
host Kernel RaidType raidlevel #disks DiskType DiskSpeed (RPM) CPUInfo mhz RAM(M) testsize K/sec K/sec K/sec K/sec K/sec
nat1-single disk 2.6.8 none
1 ide 5400 (1) Pentium 165mhz 165 128 6G 1491 10495 5256 1730 11514
Xena raid1 2.4.22 Hardware 1 2 scsi 10000 (2) Intel(R) Pentium(R) III 1400Mhz 1400 2000 3G 15682 33073 12604 16394 24242
Fred-degraded 2.6.7 Software 1 1 scsi 10000 (2) Pentium III (Coppermine) 1.0Ghz 1000 2000 10G 14862 20169 11823 16140 28471
Fred raid1 2.6.7 Software 1 2 scsi 10000 (2) Pentium III (Coppermine) 1.0Ghz 1000 2000 10G 14653 19625 11453 16608 28788
Fred single disk 2.6.7 Software 1 1 scsi 10000 (2) Pentium III (Coppermine) 1.0Ghz 1000 2000 10G 14808 22059 12871 16381 31871
Bud raid1 2.4.22 Software 1 2 scsi 10000 (2) Intel(R) Xeon(TM) CPU 3.06Ghz 3000 1000 10G 24288 38629 21496 25724 48377
squirrel single disk 2.6.9 none
1 ide 7200 (1) Intel(R) Pentium(R) 4 CPU 3.00Ghz 3000 512 10G 33913 35521 18886 26427 52242
brien-degraded 2.6.9 Software 5 2 ide 7200 (2) Athlon XP 1.53Ghz 1500 512 10G 18619 20690 16483 26114 52297
brien-raid5 2.6.9 Software 5 3 ide 7200 (2) Athlon XP 1.53Ghz 1500 512 10G 20756 20477 16935 26764 62454
brien single disk 2.6.9 none
1 ide 7200 (2) Athlon XP 1.53Ghz 1500 512 10G 25492 33957 22044 27278 63052
Gasp raid5 2.4.22 Hardware 5 4 scsi 10000 (2) Intel(R) Xeon(TM) CPU 2.80Ghz 2800 4000 10G 20936 24329 17461 25829 89098


--brien