BLKMGK Wrote:A standard RAID can lose a disk and not lose data. However losing TWO disks often means losing ALL data unless you've added still more disks to the array for redundancy.
I can't say for all RAID systems, but with ZFS you can choose your preferred level of redundancy. For example, if you're happy with the capacity of one disk for parity data then you could choose a simple 2-drive mirror, or RAID-Z1. If you want more safety then you can choose double-parity like RAID-Z2. If you want triple-parity then you can choose RAID-Z3, which allows three drives to fail before you lose any data.
So depending on your wallet / paranoia level, you can choose a level of data safety that suits your own situation.
BLKMGK Wrote:Likewise a standard RAID spans files across many disks - the advantage being FAST data access as you get data from multiple disks at once. However this means they all must spin to get access to the data. unRAID doesn't span disks like that and stores parity on a dedicated drive with other drives using REISERfs which is a standard F/S. Downside being that the array doesn't appear as a giant volume (shares take care of this) and that it's not as fast. However for spitting out even the highest def video you do NOT need uber fast transfer rates so this is good. unRAID is NOT meant for enterprise storage, it's meant for home media primarily and it serves this purpose VERY well.
Why not use enterprise-level data safety mechanisms that are *free* and available within ZFS? What happens with unRAID if your parity drive dies, or one or two of your data drives dies? With ZFS, using RAID-Z2, if *any* one or two drives die you lose no data, and you can rebuild any dead drives so *no* data is lost.
BLKMGK Wrote:ZFS I cannot speak to. I have researched it some because it's always something put forth as a solution but I'm not sure how you would set this up booting from a USB stick etc.
USB sticks are not generally suitable for booting OS's from as they tend to write frequently to the devices (logs etc), and this will reduce the life of the USB stick. They are also fairly slow to boot from.
BLKMGK Wrote:and I think Solaris x86 and BSD (?) are the only ones with real support. Solaris is a bit shaky so far as corporate support right now I think and i'm not sure how friendly BSD is. unRAID however is pretty simple I think and lots of folks are on the suport forum willing to help...
Solaris has corporate support from Oracle.
Also, for ZFS newbies there is a great forum available on the OpenSolaris.org site which is frequented by very knowledgeable & helpful ZFS users - see here, including Oracle staffers: http://opensolaris.org/jive/forum.jspa?forumID=80
ZFS is simple - here I will create a 6-drive array which can survive any two drives failing before any data is lost:
# zpool create tank RAID-Z2 drive1 drive2 drive3 drive4 drive5 drive6
Now we'll create a file system to store our movies in:
# zfs create tank/movies
Now we'll create a 'share' so that our movies can be shared to other devices like computers around the home, or HTPC / media center:
# zfs set sharesmb=on tank/movies
Voila, what's hard about that?
Now, for one of the killer features of ZFS, that virtually no other RAID system has -- the ability to find and repair all files that have become corrupt due to 'bit rot':
# zpool scrub tank
This last command will read the contents of *all* files within your storage system and compare each block with a 256-bit block checksum. Any blocks not matching the checksum will be recovered by using the parity data stored when the file was originally created. This feature is priceless and gives you peace of mind that your data is 100% correct as it should be. Can unRAID or FreeNAS do that?