March 9, 2010 at 6:48 am
Trying to get my head around a couple, as I can imagine they are both risky.
We have Server A. It is a RAID 1+0. It contains 4 disks of 150gb each split into 2 arrays (150gb data available to the each). Array 0 hosts the C and D, Array 1 hosts the E.
Now if just 1 disk failed, I think this would be in trouble surely?
Server B. RAID5. Contains 4 150gb disks of 150gb each with just 1 array (don't ask).
410gb available to the server.
Am I right in thinking this one, despite being hideous, would be ok with 1 disk failure as the spare disk would pick up? Or would we have data loss depending on the disk because the spare is too small to hold all?
Bit confused. Always learning!
March 9, 2010 at 9:48 am
Shark Energy (3/9/2010)
Trying to get my head around a couple, as I can imagine they are both risky.We have Server A. It is a RAID 1+0. It contains 4 disks of 150gb each split into 2 arrays (150gb data available to the each). Array 0 hosts the C and D, Array 1 hosts the E.
Now if just 1 disk failed, I think this would be in trouble surely?
Server B. RAID5. Contains 4 150gb disks of 150gb each with just 1 array (don't ask).
410gb available to the server.
Am I right in thinking this one, despite being hideous, would be ok with 1 disk failure as the spare disk would pick up? Or would we have data loss depending on the disk because the spare is too small to hold all?
Bit confused. Always learning!
Shark,
I'm not sure if I fully understand what you have here.
Lets take server A
If you have Four disks that make up two RAID hardware arrays, two disks in each RAID configuration then they can't be RAID 10 (Mirrored and Stripped) or RAID 0+1
They will either be RAID 1 or RAID 0.
If you have 1 RAID hardware Array, made up four disks then it is possible that these can be configured into a RAID 10 configuration.
Now lets assume, because I think I'm reading it right, that you have two RAID arrays of two disks each for server A. If these are configured as RAID1 (Max 150 GB space on each array) then you can, in theory lose a disk in each array and keep going on the mirrored pair.
If its RAID 0 then you can't lose any disks without losing all data stored on that array...This would be the riskiest configuration
Server B - Four disks of 150GB configured in a RAID 5 setup you have 450GB available for storage 3 disks for storage, You lose 1 for parity. You can lose one disk in this setup and not lose the data.
I think I am right here but I'm no storage expert either so hopefully someone will correct me if I'm wrong.
Hope that helps
Gethyn Elliswww.gethynellis.com
March 9, 2010 at 10:06 am
Thanks for that. The Server A scenario is sadly real - or is reporting as such anyway. Under the HP Smart Array utility it is showing as RAID1+0, but is only showing the 4 physical disks for the 2 partitions.
Unless it would not even let you apply Raid 1+0 in this scenario (I'm not an expert) and therefore there is a problem with what it is reporting....
Very odd!
With 2 partitions and RAID 1+0 i'd have thought you would need 8 disks. The 2 mirrors and 2 stripes for Array 1, and the same for Array 2.
March 9, 2010 at 2:59 pm
I found this forum question that could explain how HP handle a 2 disk RAID1+0...
So in my situation, we have 2 146gb disks making up Array 1.
The files are striped between the 2 disks using 73gb of the data on each.
The files are then mirrored between the 2 disks in the other 73gb per drive.
So in effect, File 1 loads to Disk 1, File 2 Loads to Disk 2, File 3 loads to Disk 1. File 1 is mirrored to Disk 2, File 2 is mirrored to Disk 1, File 3 mirror to 2.
And so forth. So its not a natural RAID1+0 set up where you are striping between Disks 1 and 2, and mirroring to 3 and 4, but it is a cost effective alternative, and possibly not much of a performance hit. In fact it may provide better performance!
Does that sound right? I think I've finally got there!!!
March 9, 2010 at 3:13 pm
Shark
I read the first few posts of that HP forum, it seems from that they treat a 2 disk array configured as raid 10 as Raid1 which is what I thought initially.
I'm not well read on HP smart arrays specifically so can't make to much of a comment on that particular technology.
If you need anything further then just shout, glad you feel like you have made some progress
G
Gethyn Elliswww.gethynellis.com
March 9, 2010 at 3:35 pm
Thanks Gethyn, appreciate it.
EDIT: http://episteme.arstechnica.com/eve/forums/a/tpc/f/833003030931/m/639000063041
I can't believe my head came up with a method of actually trying to allow RAID1+0 onto 2 disks which would be totally pointless and useless.
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