[mythtv-users] Storage Questions. LVM, RAID, NFS

[Robin Gilks]

> Thanks, guys!
>
> It sounds like Raid 5 is the way to go -- I'll order the hard drives
> today!
>
> One more quick question:  I currently have two first generation SATA
> drives, and will be adding 2 SATA II drives, and 1 P-ATA drive.  I
> imagine that the slower drives will slow the whole process a little
> bit (hopefully insignificantly?).  My question is this:
>
> Given that I'll have a wide variety of drives, will it make any
> difference how much of a buffer the drives have?  (8MB vs 16MB)   Any
> other suggestions (like buying from different manufacturers to avoid
> disks dying at the same time) that I should be aware of?

A word of warning about controllers, cables etc. This is what I've just
discovered on my own system and may be relevant to others.

I have 2x PATA 250G drives partitioned as 50G raid1, so I have a full
mirror (raid1) for the OS and stuff I REALLY don't want to lose such as
email and 200G raid5, and 2x SATA 200G raid5 to give a total of 4x 200G
partions in the raid5 array. This array gives me 600G of raw space that
has LVM2 on it to split it into resizable partitions with various
filesystems appropriate to the data being stored (eg. JFS for Mythtv
recordings, ext3 for pictures)

The way I USED to connect them:
 - the pair of 250G PATA drives on one port of the m/b controller
 - DVD writer + exchangable drive on the other PATA m/b port
 - the pair of 200G SATA drives on the m/b SATA ports

Note that the raid1 disks were on the same cable - BAD NEWS. A few tests
after having problems burning DVDs showed I was getting transfer rates
down at about 4M/s - probably because both raid1 and raid5 want to write
to 2 disks at once which can't be done if they are on the same controller
port!!

The way I NOW connect them after dusting off an old PCI IDE controller:
 - the pair of 250G PATA drives on seperate ports of the m/b controller
 - DVD writer + exchangable drive on a Promise Ultra100 TX2 PCI card
 - the pair of 200G SATA drives on the m/b SATA ports
Without having to change any conf files, the raid arrays configure
themselves in the new arrangement and my transfer speeds are up to 18M/s


-- 
Robin Gilks