back to article Virtualised storage: the perfect space-saving solution

In case you have been living under a rock for the past month or so, we are in the middle of a hard drive shortage. Now that we can’t simply add more drives at will, storage utilisation has suddenly become important again. It should not have taken this crisis to shine a light on this topic; we are reminded at regular intervals …

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All horribly wrong! ... who verified this article before publishing it ?!

Storage Virtualisation does not magically fix storage issues like the article suggests, it is NOT a replacement for RAID!

If you think a double disk failure in a RAID-5 set is bad wait till you see what happens when you get a double disk failure in a RAID-5 set that is incorperated into a virtualised storage pool ... Instead of hosts only using that RAID set losing storage, ALL your hosts using the pool lose their storage .. how fab is that! ;-)

It does however provide a very good method of moving your servers/applications LUNs about between storage tiers without the host being aware.

It also provides a method for better utilising your storage capacity (GB and IOPS), though you still have to be sure that you still keep data seperate that should be seperate (Logs and databases still shouldn't live in the same pool)

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Megaphone

RAID 5?

WHAT? Please read this: http://www.zdnet.com/blog/storage/why-raid-5-stops-working-in-2009/162

Then please, PLEASE, never use RAID 5 ever again. RAID 10 or RAID 6, minimum. Using RAID 5 is almost as unpardonable as using “RAID” 0.

I've seen RAID 50, 51, 60 and 61 becoming far more common for larger arrays, but this is really controller dependant.

Far more importantly, I wouldn’t trust a centralised filer that didn’t do synchronous block-level replication to a twinned partner device. In my environments I’ve moved entirely to “twinned” RAID 10 for high-demand data, and twinned RAID 6 for bulk storage. (Effectively RAID 110 and RAID 61.)

All of that needs to be borne in mind with the idea that RAID IS NOT BACKUP. You always must plan for array failure. Always.

Additionally, please bear in mind that a single filer can run multiple arrays. The failure of a single array on a filer does not mean the loss of all LUNs on that filer. Merely the loss of the LUNs on that array. (And frankly, if you are set up right, it should automatically fail over to the “twin” system at that point anyways.)

I agree that storage virtualisation isn’t a magic wand. You don’t solve all your problems simply by buying a filer from EMC or IBM.

Storage virtualisation is a good way to drive up utilisation, reduce disk usage and solve a host of many and varied problems. Overall, it is a more efficient – and probably quite a bit more safe – way to do storage. But it does absolutely require careful planning and execution; otherwise it can indeed be quite the disaster.

Just like anything else in IT.

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Linux

Totally agree RAID5 = Disaster

I have been burned by RAID5 sets with 1 drive failing then another drive has already 1/2 dead and shows its defective side once the replacement drive is inserted.

RAID50 is what I am running in the SAN's, however I opted to go with RAID10 on standalone servers (for video).

RAID0 & RAID5 are like snakes, they do their worst work after a disk drive fails. You put a new one in and the machine crashes and you are left with a blinky courser.

The day the mechanical hard-drive can go to a permanent retirement will be a wonderful day. One can only hope static ram will eventually come down in price and not be unattainable at the current prices. Plus the I/O is amazing with static ram, I checked out the RAM SAN prices and they are still pretty high.

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N72

Another Virtual Operating System App Recommendation

Prayaya V3 is a virtual operating system tool to help you build your PC "On a stick."

Sounds weird right? Ok, plz allow me to do some explanations here, "stick" here refers to any portable devices like iPod, USB hard drives, iTunes and even your mobile phones.

With Prayaya V3, you could install your PC operating system on the mobile device so that as long as you take the device with you , it means that you have your whole PC. It offers people much convenience.

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