I want a rubber/lego/meccano hard disk …

January 6, 2014

Stop sniggering. This is not about being able to drop a disk from a great height and have it survive … it’s about me making my own disk. Now that sounds as dumb as anything I’ve put in a blog before, but let’s look at it. What exactly do I want from the disk in my server?

  1. It has to be big – as big as I want to make it (512Tb should be enough)
  2. It has to be redundant – and I want lots of options on how redundant I make it (because I’m a gambler at heart like most IT pros and want to be able to determine just how close I sail to disaster J)
  3. It has to be fast (SSD or faster is what I mean) – but I want to be able to determine how much of it is fast and how much is “other” (other being big, fat, cheap, SATA)
  4. It has to be cheap (SATA) … this works with points 2 and 3 above – the price will come down with less redundancy but will go up with more speed … but I want to be able to configure this disk the way I want it with any combination of the above
  5. It has to manage itself … because like all IT pros I like playing with things for a while, but then get bored of such menial tasks pretty quickly
  6. So it has to look and feel like one large hard drive with all of the above characteristics

So let’s summarise what I’m after here …

“a large, redundant, flexible, configurable, fast, cheap, self-managing disk”

Hmmm …

Not asking much am I. Seagate make “hybrid” hard drives … spinning drives with some NAND flash built in … and they use some fancy algorithms to work out what should go where. Only problem is that they are a bit limited in size – I want a 20Tb disk (or larger) and it will be a while before I see something that large in a single disk.

Enter maxCache Plus. This clever technology lets me take any storage in the server and combine it into a single self-managing disk. While that sounds groovy, let’s look at a little more practical solution.

You need big capacity so you purchase 16 large enterprise sata hard drives (4tb enterprise SATA). However there is going to be data on this disk that needs to be fast (random, database type material), as well as large amounts of nothingness (ie it’s a VMware machine). So instead of wasting ports on your RAID controller, you purchase a Flash Drive (NAND flash drive such as Fusion IO) to accelerate certain data.

Grab yourself an 81605ZQ, plug all the drives in (doesn’t matter if they are 6gb or 12gb drives), make a RAID 5 with a hot spare and you’re ready to go. Only problem is speed – it’s not fast enough. So stuff the RAID 5 into a “pool” in maxcache (it will be Tier 1 – the slower of the two storage pools). Then grab your Fusion IO or other Flash Drive and stuff it into Tier 0 (the faster of the two pools).

Now grab the storage from both pools (Tier 0 and Tier 1), and combine them together into a single disk (Virtual Volume) that lets you see the capacity of both storage devices, moulds them into one disk and manages the data positioning for you.

So maxCache, in this environment, will move blocks of data around within the virtual volume, repositioning hot data onto the Fusion IO portion of the storage (Tier 0), and moving the not-so-hot stuff onto the RAID 5 array. And what management do you need to do? Sit back, grab a cold one from the fridge (after 5 of course) and put your feet up – there is no user management of the data volume required.

Sounds a bit too good to be true … a disk that is made of up a Fusion IO-like card, a large RAID array of whatever redundancy level I want, made out of whatever storage I have in my system, not just attached to my RAID card, all managing itself and constantly optimizing the customer data onto the best storage medium for the data type.

What I didn’t mention is that I can actually chop up the Flash Drive and RAID array into different pieces so I can make multiple disks – maybe even one with a lot of flash and reasonable amount of SATA, and one with very little flash acceleration and mostly SATA – either way the choice is mine. In other words, it is “flexible” (to a crazy degree).

So I end up with a “large, redundant, flexible, configurable, fast, cheap, self-managing disk” (or disks). But wait … I don’t want to buy a Fusion IO card … I have a 71605E (entry card) sitting on the desk and good fast SSD are cheap as chips these days. No worries – plug the SSD onto the 7 series, stuff it in next to the 8 series, make a raid 10 of ssd arrays (doesn’t need cache on controller or ZMCP cache protection on 7 series for this). Then you can connect up to 16 SSD and use that as Tier 0 storage instead of a flash drive.

So what limits the configuration possibilities? The grey matter between your ears – pretty much your imagination. In other words this really is a flexible and highly configurable technology.

Ciao
Neil

 

 

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