Noob Centos Admin schrieb: > > > On Thu, Feb 19, 2009 at 4:22 AM, Ray Van Dolson <rayvd at bludgeon.org > <mailto:rayvd at bludgeon.org>> wrote: > > The other side of the coin (as I think you mentioned) is that many are > not comfortable having LVM handle the mirroring. Are its mirroring > abilities as mature or fast as md? It's certainly not documented as > well at the very least. :) > > > I remember googling for this before setting up a server some weeks ago > and somebody did a benchmark. The general conclusion was stick to md for > RAID 1, it has better performance. IIRC, one of the reason was while md1 > will read from both disk, LVM mirror apparently only reads from the > "master" unless it fails. "md1 will read from both disk" is not true in general. RAID1 md reads from one disk only; it uses the other one in case the first one fails. No performance gain from multiple copies. You can easily see this for yourself by setting up a RAID1 from e.g. sda1 and sdb1 - /proc/mdstat is: Personalities : [raid1] md1 : active raid1 sdb1[1] sda1[0] 104320 blocks [2/2] [UU] and then comparing the output of hdparm -tT : /dev/sda1: Timing cached reads: 29368 MB in 2.00 seconds = 14711.93 MB/sec Timing buffered disk reads: 100 MB in 0.92 seconds = 108.79 MB/sec /dev/md1: Timing cached reads: 28000 MB in 2.00 seconds = 14023.66 MB/sec Timing buffered disk reads: 100 MB in 0.95 seconds = 105.81 MB/sec /dev/sdb1: Timing cached reads: 23780 MB in 2.00 seconds = 11907.30 MB/sec Timing buffered disk reads: 100 MB in 0.98 seconds = 102.51 MB/sec To get performance gain in RAID1 mode you need hardware RAID1. HTH, Kay