Re: Suggestion for PCI IDE controller?
From: Steve Wolfe (unt_at_codon.com)
Date: Sat, 26 Jun 2004 18:48:16 -0600
> For situations where you write a lot more, I would recommend RAID1 (aka
> mirroring). There you only multiply your writes only by 2x (instead of 5x
> I/O). Reading is also considerably improved (if software is smart enough)
> since it can choose to read the data from either disk, depending on the
> head position and whatever other factors the drivers use for optimization.
I took some SCSI drives a while back, and had a very hard time getting any
significantly better write performance out of RAID 1 than I did from RAID 5:
> As for network being the bottleneck: probably, if you have very fast
Unless he's got gigabit networking, the network *will* be the bottleneck
unless he's got extremely slow disks. With 100mbit ethernet only handling
10-11 megaBYTES realistic throughput per second on a full-duplex, switched
connection, it doesn't take much disk at all to keep up. And even with
gigabit controllers and a gigabit switch, it takes a very potent machine
indeed to handle *file sharing* at gigabit speeds, even if you've got an
incredibly fast disk array.
> Also consider your UPS. RAID with corrupted writes is trashed. I don't
> think you can recover like from a failed disk.
I don't see why it wouldn't be just another inconsistency in the array
that gets handled in a resync, as far as the md device goes. As for the
file system, it gets fsck'd, or the journal recovered.
> RAID is not replacement for backups!