striping or concatination? striping means yes same size spaces, but you can just concatinate which simply means adding together. So 12+5+4= 21, you could then mirror against the 20 gig in software and only loose 1 gig. Whether the controller is bright enough to tell the difference is another matter. Thing -----Original Message----- From: Steve Wray [mailto:steve.wray@paradise.net.nz] Sent: Wednesday, 20 February 2002 3:54 To: linux-lvm@sistina.com Subject: [linux-lvm] lvm and 'poor mans raid' on heterogenous hard drives! Hmmmm, Ok so I have 4 hard drives of very varying capacity (20G,12G,5G,4G) I have an off-board IDE controller (Promise 66) I think 'maybe I can take advantage of the IDE system and put a drive on each master and stripe them.' A hardware RAID card would be suboptimal because (as I understand it) the striped volume could only be as big as the smallest drive. So, I set up the drives as; hda = 20G hda1 = 64M and is /boot hda2 = 1G hdc = 12G hdc1 = 1G hde = 5G hde1 = 1G hdg = 4G hdg1 = 1G The other partitions are set up for various other volume groups and non LVM system partitions. hda2, hdc1, hde1, hdg1 are added to a VG 'fast' The other LVM partitions on hdc-g are in a volume group that doesn't see much traffic, just storage. I make logical volumes on fast striped across 4 drives. So thats 4 partitions at the beginning of the drives, with volumes striped across them. I expected some performance improvements. So I get the iozone benchmark and start running it on the system. I compare performance of striped volumes with performance of a volume purely on hda. Interestingly, the performance improvement is not dramatic, I expected better. The main improvement seems to be that the striped volumes do better with larger file sizes and as file size increases the striped volume keeps its performance up better. I'm a newbie at this benchmarking lark, so if anyone wants the excel spreadsheets generated from iozone just ask, I'd like a second opinion! There are some strange things, like when file size gets above 16M performance drops dramatically regardless of striped or linear volumes... Maybe its something to do with extents? _______________________________________________ linux-lvm mailing list linux-lvm@sistina.com http://lists.sistina.com/mailman/listinfo/linux-lvm read the LVM HOW-TO at http://www.sistina.com/lvm/Pages/howto.html _______________________________________________ linux-lvm mailing list linux-lvm@sistina.com http://lists.sistina.com/mailman/listinfo/linux-lvm read the LVM HOW-TO at http://www.sistina.com/lvm/Pages/howto.html
