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I got a esxi server with 2x 3tb HDD these 2 disk are not in raid , so i got 2 data stores

my vms use one datastore or the other as system disk

I would like to have a safe storage place shared between my vms

I'm planning to setup a VM which use a virtual disk from each datastore in software Raid 1 to make a safe storage place.

I know that it's not the best way of providing safe storage but i would like to know if there is any potential issue with that.

Lets say i will use NexentaStor for example with 2* 400 gb disk (virtual disk) mirrored.

Is there something wrong with that ?


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Define "safe". If you mean fault-tolerant, then the answer will be different than "able to recover from data corruption" or "able to recover from accidental deletion" – MDMarra Nov 18 '12 at 18:00
safe as fault tolerant - able to recover from data corruption or able to recover if a disk fail – Bgnt44 Nov 18 '12 at 18:07
And why can't you just mirror the two disks that you have now? – MDMarra Nov 18 '12 at 18:38
The hardware won't allow RAID. – ewwhite Nov 18 '12 at 20:35
Yikes, then it really doesn't belong hosting VMs unless you do a MacGuyer and RDM all of the disk to Nexenta and export it back to the ESXi host. – MDMarra Nov 19 '12 at 1:23
up vote 3 down vote accepted

Start again and RAID1 your 3TB disks. Performance will suffer in that you can't split between spindles, but you really do not want your VMDK's on non-RAID disks.

If you do as you suggest, then your 2x 400GB disks will be fault tolerant, but the system that serves that data will not be. So you're not going to prevent any downtime - and as we all know, RAID isn't there as a substitute to backing up...

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I'm assuming the system hardware in use doesn't have hardware RAID capabilities. – ewwhite Nov 18 '12 at 18:10
@ewwhite Potentially, then I'd argue it's not a good candidate for local VM storage. The question reads that he already has systems running off 'one or the other'. Dangerous! – Dan Nov 18 '12 at 18:11
of course the system dont have hardware Raid ability otherwise it would be an nobrainer question :) – Bgnt44 Nov 18 '12 at 19:45
If i choose nexentastor as NAS, i can install the system on both datastore as soft raid 1 too (2x10gb), that mean at least nexenta vm and the 400gb content will be safe against fault , isnt it ? – Bgnt44 Nov 18 '12 at 19:51

If you want fault tolerance and the ability to recover from corruption, then you need two different things.

You should use RAID, first of all. I'd recommend RAIDing the two disks and presenting it as one datastore. If you can't for some reason, then you shouldn't use this box to present storage to the VMs. If you still must, then use software RAID inside of the VM, but that;s ugly. This will address fault tolerance.

If you need to recover from corrupt data or deleted files, then you need backups. RAID is not a backup, it will happily copy corruption or mangled data to the other disk in the mirror without thinking twice about it.

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