I currently have 2 x 250GB drives in raid 0 (software raid) is it possible to have
1 x 250GB + 1 x 750GB in 1TB Raid 0
and
1 x 1TB Drive Raid 1 of the Raid 0
and sell off the other 250GB drive
If you build a stripe set out of mismatched capacities, the overall capacity will be based on the smallest disk. That is, if you've a 250GB + a larger drive, 750GB in this case, you'd only get 500GB of usable capacity. The remaining 500GB would be inaccessible, unless you partition the 750 into a 250 and 500GB partitions.
Even if you do this, there's a couple of issues to be aware of.
- You can have performance issues if you try to access both partitions on the 750GB disk at the same time (simultaneous access).
- There's also additional wear and tear on the 750GB, as it will be accessed more often than the 250GB disk that comprises the stripe set with the 250GB partition.
Hence the reason to stick with same capacity disks, and if possible, the same models.
OK, that's the end of the "Quick and Dirty" with the drives you're trying to do with what you have.
If you'd like more information on RAID in general, I'd recommend giving the
RAID Wiki a thorough read.
BTW, the MP is capable of 0/1/10 only (10 is safer than 01, and IIRC, Disk Utility only allows 10 for that reason).
As per your situation, I'm with
Honumaui here; what are you trying to do and why? And what is your backup scheme (you need one, whether RAID is used or not, but especially with striped sets)?
Please understand, the information you provide can help steer you in the right direction.
You want to run raid 0 so if your using a 250 gb and a 750 gb harddrive in raid 0 all your going to have is 250 gb's of storage
If you use two different sizes of harddrives the smaller harddrive will be dominate..
500GB, not 250GB. But the total capacity is based on the 250GB disk (always the smallest member; same goes for other levels).
Also if you want a raid 0 (stripping) with raid 1 (mirroring) you will need to run raid 10 which will need four harddrives. And still only have a usable space of 250 gb.
Technically, what you've described is a 1+0 or 10, not 0+1 or 01. The order you proceed makes the difference. So if you start with a stripe set, it's 0+1. 10 starts with creating both mirrors first, then striping the pair of mirrors together.
And assuming the capacity is based on 250GB as the smallest drive, the overal capacity would still be 500GB, not 250GB.
Also software raid is pretty much pointless.
Not necessarily. It can allow users to save money on levels that have little overhead to operate, such as stripe sets. 1 and 10 are also light on resource requirements, and are acceptable for software implementations for many as well.
It all depends on the specifics, but cost usually trumps everything else for most users. And unfortunately, software RAID has a significant advantage over hardware RAID implementations in that regard (not just the cost of the card, but you need to use enterprise disks with a proper hardware RAID card, and they're more expensive per disk as well, so it's worse than many would expect).
Unless you are doing some data sensitive video work or something just do normal backups daily and you'll be fine modern day harddrives are quite reliable if you buy good brands such as Seagate or Western Digital.
Sadly, the majority of drive makers are sporting ~10 - 13% defect rates lately for their consumer drives.
Which is worse than past figures, in case you're wondering.
That said, they're not all that bad yet, and consumer disks are cheap enough to be considered disposable. Seriously, when compared to the value of the data stored on them (even personal use IMO, as family photos and movies are priceless to many).
or Raid 50 .......
Not unless the OP springs for a hardware RAID card, and sufficient enterprise disks to go with it.
Besides, you don't want to run parity or nested parity arrays in a software implementation, due to the fact it can't deal with the write hole issue.
