Software Raid5

Si.

Si.

Si.

Soldato
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Having just lost a 3TB drive I think it's time to switch to Raid5. I dont have a suitable Raid controller so thinking of going to software Raid on my 2012 server. Does anyone use this? How reliable is it?

I appreciate that I may loose some performance but data integrity is more important than the slight loss in speed.

Also, is it possible to set the Raid up with 3 drives and add a 4th at a later date without having to recreate the volume?
 
In terms of data integrity a dedicated RAID controller will always be better than software.

How is your operating system set up? I'm not sure how easy it would be/or even possible to recover data if the drive holding the operating system became corrupted - Therefore a RAID 1 setup for the OS is pretty imperative.

Someone else may need to answer the question about extending the RAID as i've never needed to before. Although i can't see why it shouldn't be possible. But the RAID would need to be reinitialised in order to redistribute the parity across all disks.
 
Semple said:
How is your operating system set up? I'm not sure how easy it would be/or even possible to recover data if the drive holding the operating system became corrupted - Therefore a RAID 1 setup for the OS is pretty imperative.
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OS failure won't be an issue.
 
Semple said:
In terms of data integrity a dedicated RAID controller will always be better than software.
Click to expand...

This is utterly wrong, RAID controllers are no better than software implementations of RAID, it all about which implementation you use and how you plan on using it. I'd pit ZFS against any RAID controller you'd find in any server. If you want to look at software RAID take a look at the likes of ScaleIO, Nexenta, Sansymphany.

Server 2012 has some nice features for storage, you still have the option of Dynamic Disks and a new feature called storage spaces. This will allow you to grow later your volumes later on as you add more disks, but you have to add them in specific amounts, you can't just add another disk to expand a parity volume.

Regardless, RAID does not protect you against logical failures such as deleted files etc... always, and I mean always back up your important files.
 
I'm not bothered about logical file deletions, just drive failures.

Does Server 2012 write the volume.RAID configuration on to the drives? so a rebuild of the OS should the OS drive fail will not destroy the RAID volume?
 
Storage Spaces in Server 2012 are portable, just make sure all the drives are visible to the new OS installation and you can import the config.

Storage Spaces aren't very high performance though, especially for parity. Do some reading into it if you can, it's nice tech but not quite there... plenty of improvements in R2 though, including performance.
 
ZFS is as power full if not more so than most/all hardware raid controllers, it is limited to certain operating systems unfortunately
 
I've been testing out storage pools on a VM and don't think it really adds anything over a standard software RAID5 setup created through disk manager. I thought it would allow me to add in a new drive should I need to but can't seem to get it to work.

It's just a shame you can't add in an additional drive to a standard RAID5 setup (or I can't find a way to do it). Reason that would be handy is I'll initially have 3 drives, but likely getting a 4th in 3 months or so but to add it I'll have to remove and re-create the RAID5 volume from scratch which will be difficult.
 
Frozennova said:
ZFS is as power full if not more so than most/all hardware raid controllers, it is limited to certain operating systems unfortunately
Click to expand...

I totally agree, i'm using Freenas with a 4x 3TB RAIDZ volume, I get around 100-117MBps from it when transferring files, so it's practically maxing out 1G Ethernet if you include overheads.

In the past i've tried various other RAID options, software and some "moderately priced" controllers, but ZFS seems to be the best by far (unless you want to drop £thousands on a netapp or something lol)
 
I'd even like to add that software RAID generally is more reliable than hardware controllers when you consider that hardware controllers use volatile cache with a battery. Sure servers should have dual power, yes the battery should last for several days in the event of a power outage but you are trusting a battery to store your data in the first instance (cache is the first hit device on a RAID card). Many software implementations of RAID such as ZFS / Datacore does use Cache but the writes are not acknowledge until they are committed to disk.
 
RAID controllers have dedicated resources and aren't quite as vulnerable to instability as even the best software RAID implementation.

SEGFAULT a Solaris kernel and, with the best will in the world, your ZFS cached writes are gone. Not true of a hardware RAID controller as it is in charge at that point. If the application is on the same box as the disk and you're thrashing your CPU, your disk performance is going to suffer - again this isn't true of a hardware RAID device. The battery is a risk, yes - but most modern controllers won't cache writes if they suspect the battery isn't up to standard. Hell, a NetApp controller won't even boot until the batteries are charged!

I think you could argue one way or the other for the rest of the evening but the fact remains that a properly maintained battery-backed hardware RAID controller is the least exposed method for running your arrays...
 
Only downside of software RAID5 is the speed.

I ran software RAID before getting 2x Dell Perc 6i controllers as I was getting fed up on my machine thrashing when copying large files.
 
Well, received 2 new 3TB drives this morning and I've configured a software RAID5 using 3x3TB drives. I decided just to go with standard "Disk Manager" RAID5 rather than using storage pools.

It's currently resynching the 3 drives which I didn't expect to to do since there is nothing on them yet. I'll copy data to them once this is complete (Although I expect this will take some time).

UPDATE:

I expect the resynching to take a long time.. too long so I've dropped the RAID5 and gone for a parity storage pool instead.. still not sure which is the best option :S
 
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