David Konerding wrote:
It would be very possible that your file data would span the two disks on the channel
Yes, but the data is lots of small files so this should be a rare event.
or that two processes would be accessing the disk simultaneously across both disks on the channel.
The current system already has four disks on two channels, configured as a single linear volume. So the problem of simultaneous access on the same channel from two processes already exists. I am trying to make the best of a bad situation :-( I suspect I will end up buying a four channel IDE RAID controller.
I believe LVM supports nested mirroring and striping, so I see no reason why it wouldn't work. I see two scenarios -
______disk0 Ch.A ----<______ disk1 ______disk2 Ch.B ----<______ disk3 1. make the two disks on each channel linear volumes and stripe across the two linear volumes: vol_1 = disk0 + disk1 vol_2 = disk2 + disk3 s_vol = vol_1 stripe vol_2 2. make two stripe volumes across the controllers and then combine them into a linear volume vol_1 = disk0 stripe disk3 vol_2 = disk2 stripe disk1 l_vol = vol_1 + vol_2 Do you have any opinion which would be best solution given that the filesystem runs at near full capacity.? How would I go about achieving this via LVM?
Disk arrays normally need tuning to provide the performance enhancement you think it should be able to achieve.
What tuning options are there? Are you talking about stripe size? How does one determine the best stripe size for a volume (apart from empirical tests)? -- Simon Oliver