Hi
I have some strange performance results on a raid0
I have 4 IDE disks on two controllers, the one on the motherboard of the duron 1 GHz mackine, the other a promise TX2 plus SATA + PATA controller. I run kernel 2.4.22
The disks and hdparm -t on each of them
/dev/hdc1 seagate 80 GB 16 MB/s /dev/sda1 maxtor sata 200 GB 50 MB/s /dev/sdb7 maxtor 160 GB 54 MB/s
Well, if you're lucky, these might be useful as comparative numbers between the different drives on the same system. Just as likely not, though, hdparm rather sucks as a benchmark.
The partitions are al about 5 GB each.
If I make a raid0 device of all of them I get a thruput of 45 MB/s IIf I exclude the hdc1 partition, I get around 75 MB/s. The system is a little loaded - but that would be normal operating conditions. CPU is 90 % idle. I have about 100 MB free RAM.
Let's assume that the above numbers have a basis in reality. :) If you've got disks with widely varying speeds, then the best performance can often be hand from setting up a linear RAID volume, rather than a RAID0. RAID 0 is really designed to have matching disks, as it distributes data evenly across them. With Linear, and ext2 (erm, I'm assuming 3 as well, I haven't heard anything different), you can sometimes get better performance with smaller writes, because ext2 "scatters" data around the filesystem, in order to avoid fragmentation. HTH,
Greg
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