[CentOS] using Linux as a NAS / SAN device

Rudi Ahlers wrote:
> 
> The thing is, how will these kind of option perform in a hosting
> environment where downtime isn't at all an option. We have backup
> generators, UPS, load balanced networks, etc Even the Tyan /
> SuperMicro machines that I'm looking at will have redundant power
> supplies & hard drives.
> 
> But the one piece of of the puzzle that I don't understand, will a
> self-build-Linux NAS device, or even Openfiler / FreeNAS give us that
> kind of uptime.

High quality servers running an enterprise linux version can give you 
the same uptime as dedicated hardware if you are comfortable with not 
doing updates.  For example I still have a RH 7.3 based box running that 
has only been down a few minutes in about 7 years (had to move it) but I 
wouldn't try that with anything exposed to the internet.  I did replace 
several drives and rebuild the raids over that time - and it is probably 
about to die of old age soon.

> The other thing which I would like to also get to, is that we could do
> more with a Linux based distro than with a off-the-shelf NAS. For
> example I could setup storage space for users and build custom
> applications that could manage it all - for example give a hosting
> client a reseller account with 1TB space and he could resell that to
> his clients. And I could go as far as setting up SMB / NFS / iSCSI /
> rsyn / SSH / FTP / sFTP / podcast / HTTP / etc,  i.e. other protocols
> which a NAS may not necessarily support. And I could even use it as a
> dedicated web farm if I feel like it, running HTTP & MySQL as well if
> the server has enough RAM & CPU.
> 
> Ideally I would like have a highly-redundant storage device which can
> be used by numerous users, and also host Virtual Machines on it. So IO
> will be the biggest concern, in terms of speed, with reliability the
> 2nd biggest concern.
> 
> I'll run RAID 10 (1+0) for speed & reliability, and use 1TB / 1.5TB
> RAID edition server grade SATAII hard drives with hardware RAID -
> although I also think software RAID on a decent CPU could perform
> better. But the hardware RAID cards have battery backup which gives
> better reliability. Then I would like to build 2 devices, each syncing
> with the other one.

The 2 device failover is the tricky part and it introduces some new ways 
to fail.  I've always preferred to keep things simple with mirrored 
disks in a hot-swap chassis so the likely failure (single disk) doesn't 
slow down operation and can be replaced at a convenient time.  The less 
likely motherboard or power supply failure will cause some down time 
while you swap the disks into a spare chassis, though.  And you still 
need off-site backups to cover other types of problems.

> The other question is, how well will my own Linux / UNIX based NAS
> perform? Surely these companies who build their own NAS devices spend
> a lot of time fine-tuning the OS to deliver the best performance, and
> probably spend a lot of time researching and testing different
> hardware devices and configurations to see what works best?

I'd try the canned openfiler/nexentastore installs to see if they meet 
your needs in terms of functionality and performance and if so, then 
decide whether you want to use a supported version or duplicate their 
work setting up something on generic linux/opensolaris.

-- 
   Les Mikesell
    lesmikesell at gmail.com