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Hot spare in RAID5

Noob here.

I have 4 drives. My H700 bios has 1 VD group with raid5. That group has 2 VDs. It doesn't show any hot spare configured.

Does this mean if a drive fails, I'm screwed?

Thanks.
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NVIT
Asked:
NVIT
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6 Solutions
 
lords1979Commented:
raid 5 allows for any one drive to fail without loss of data.  In raid 5, you lose about what equates to the size of one of the drives in the group for holding the compressed backup data of the drives around it
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chakkoCommented:
No, RAID5 can withstand 1 drive failing.  If a drive fails then it needs to replaced ASAP to avoid total failure.
The Hotspare drive option is the 'replacement' drive to use if one of the RAID5 drives fails.  It will use the hotspare (standby) as the replacement drive.
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mwiener1Commented:
If you have 4 drives and 2 virtual disks, then you dont have a raid 5. Double check - if its raid0, your screwed. If its raid 1 you have mirroring. You need at least 3 drives in an array for raid 5.
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lords1979Commented:
chakko, with one drive failing in a raid 5 you are still running at the time a failure.  If another drive were to fail, then you would lose data, hence my post.  And yes, three drives are required for RAID5.  However, you could have two vd if one is comprised of 3 disks and the other of 1 if RAID 5 is the first the first set.  It could have created a separate vd  for the extra drive instead of hot spare.
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mwiener1Commented:
I didn't think of that. It doesn't make any sense to do that so I guess i assumed it was as i described. No reason to put a single drive in a VD.
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NVITAuthor Commented:
@mwiener1
It shows 4 physical drives, 931 GB each, all are Online. In a tree view, it looks like:

Disk group 0, RAID5
--- Virtual Disks
  |--- Virtual disk 0, 1843 GB
  |--- Virtual disk 1, 949 GB
--- Physical Disks
  |--- 00:00:00: Online: 931.00 GB
  |--- 00:00:01: Online: 931.00 GB
  |--- 00:00:02: Online: 931.00 GB
  |--- 00:00:03: Online: 931.00 GB
--- Total free capacity: 0.0 GB
--- Hot spares
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chakkoCommented:
Some RAID controllers can  create multiple VD from 1 RAID5 stripe set.

E.G.   3x500 GB disks in RAID5,  it is possible (with some RAID controllers) to create 2 VD such as A: 300GB and B: 200GB

What I meant in my first post is 1 drive can fail in RAID5 and you do not lose any data.  If another drive in the RAID5 fails then it will be a total failure (= lose data).
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lords1979Commented:
mweinert: I totally get your point, but I have seen it all.
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NVITAuthor Commented:
@everyone

In another post, a user suggested Dell maybe set it up that way because of a 2 TB limitation in the Windows OS.
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mwiener1Commented:
That was me. Different question, different answer.
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chakkoCommented:
@NewVillageIT.  Your setup is fine, I mean there is no technical problem with that.

A hotspare disk will just mean that you have an available replacement disk (standby disk) which automatically gets used if one of the RAID5 disks fails.

You can add a Hotspare disk now or later if you want to, it won't affect the current RAID5 to add a Hotspare disk.  You just add another disk and in the Array Manager program designate the new disk as being a Hotspare function.
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chakkoCommented:
Just to add some info, if you have 2 VD then Windows (for example) will 'think' that it has 2 physical disks.
If you have just 1 larger VD, then Windows will 'think' it is just 1 physical hard drive.
The choice is yours how you want to configure it.
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NVITAuthor Commented:
@everyone,

OK. I think I see how this setup works. The total capacity available is VD0 (2 drives) + VD1 (1 drive). I don't see the space from last drive because it's the spare, right?
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mwiener1Commented:
no.

In a raid 5 you lose some drive space from the data it stores. Generally with three drives, you get a little more than the total of 2 of them as storage.

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chakkoCommented:
No, in RAID5 you lose 1 disk when calculating the Total Capacity.  Your VD0 is about 3TB.  That is the correct capacity.  You don't have a Hotspare disk.
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NVITAuthor Commented:
Sorry guys, I'm *confused*. Please bear with me.

There's 4 physical drives, 931 GB each.:

Disk group 0, RAID5
--- Virtual Disks
  |--- Virtual disk 0, 1843 GB
  |--- Virtual disk 1, 949 GB

So, VD0 is made up 3 drives, and VD1 is 1 drive? And each VD will show as a separate partition on Windows? If so, where does raid5 come in?
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chakkoCommented:
All 4 of your disks are in a RAID5 (1 big RAID5 volume).
In RAID5 you lose 1 disk capacity (that space is use for the Parity data - to protect the data in case 1 disk fails).  All 4 disks are 'mixed' together in a Stripe Set.

Sorry, before I mentioned VD0 incorrectly in the previous post, ignore that from before.

VD0 and VD1 are contained in the RAID5 volume, but there is no correlation of the VD# being connected to any particular hard disk.  Each VD# is actually spread out over parts of all 4 hard disks (the RAID5 "MIX" or Strip Set)



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NVITAuthor Commented:
Thanks everyone for helping me!
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