[mythtv-users] RAID suggestions?

[Richard Freeman]

Blammo wrote:
>
> In my own personal MythTV journey I ended up at Hardware Raid5 (3ware)
> and wish I had done it a LOT sooner. 3-4% CPU load under full-bore
> read/writes, OS independance,etc... Well worth it. Take the $200-$400
> hit (depending on the card/channels) and go HW Raid. Well worth it...


Hardware raid has a lot of advantages (including better transactional
reliability if you use a battery-backed cache), but some disadvantages
as well - cost being a big one.  Keep in mind that $200-400 will buy you
a multi-core CPU and not only make the software-raid CPU hit a lot
smaller but it will speed up everything on the system and not just disk
access.  $400 can do a lot to speed up a typical system and I'm not
convinced the RAID card is the best place to spend it unless you're
already close to cutting-edge everywhere else.

An advantage of software raid is that it is a lot more flexible - linux
allows you to reshape a raid5 if you add additional drives later - most
hardware raid solutions don't support this.  If anything does go wrong
you're also somewhat more likely to be able to recover with software
raid.  On the other hand hardware raid can provide battery-backed cache
to more safely speed up disk access and usually hardware raid cards
support high-end features like hot-swapping drives/etc.  Linux software
raid itself would handle drive swapping pretty transparently (if less
automatically in most distros) but I wouldn't go yanking cables unless
you're sure that your IDE/SATA controller won't go haywire.

Bottom line is that the decision on hardware-vs-software raid isn't as
cut-and-dried as some make it out to be - read up on it and make your
own decision.

Also - while I agree with much that has been said about the advantages
of xfs, I'm running ext3.  The main reason for this is that it is
generally better-supported on linux (ie you're less likely to get hosed
by a kernel upgrade and you'll have more friends to help you if
something goes wrong), and also it supports both increasing and
DECREASING filesystem sizes.  I like having the flexibility of
repartitioning at will using lvm2.