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Data Storage Capacity Mostly Wasted In Data Center
Lucas123 writes "Even after the introduction of technologies such as thin provisioning, capacity reclamation and storage monitoring and reporting software, 60% to 70% of data capacity remains unused in data centers due to over provisioning for applications and misconfiguring data storage systems. While the price of storage resource management software can be high, the cost of wasted storage is even higher with 100TB equalling $1 million when human resources, floor space, and electricity is figured in. 'It's a bit of a paradox. Users don't seem to be willing to spend the money to see what they have,' said Andrew Reichman, an analyst at Forrester Research."
I don't know about your data center, but ours keeps drives well below full capacity intentionally.
The more disk arms you spread the operations over, the faster the operations get, and smaller drives are often more expensive than larger ones.
Plus, drives that are running close to full can't manage fragmentation nearly as well.
Likelihood that I get fired because something important runs out of storage and falls over(and, naturally, it'll be most likely to run out of storage under heavy use, which is when we most need it up...): Relatively high...
Likelihood that I get fired because I buy a few hundred gigs too much, that sit in a dusty corner somewhere, barely even noticed except in passing because there is nobody with a clear handle on the overall picture(and, if there his, he is looking at things from the sort of bird's eye view where a few hundred gigs looks like a speck on the map): Relatively insignificant...
for a storage monitoring system.
It's so easy to over-provision. Hardware is cheap and if you don't ask for more than you think you need, you may end up (especially after the app becomes popular, gasp!) needing more than you thought at first.
It's like two kids fighting over a pie. Mom comes in, and kid #1 says "I think we should split it equally". Kid #2 says "I want it all". Mom listens to both sides and the kid who wanted his fair share only gets one quarter of the pie, while the kid who wanted it all gets three quarters. That's why you have to ask for more than you fairly need. It happens not just at the hardware purchase end but all the way up the pole. And you better spend the money you asked for or you're gonna lose it, too.
Who cares if you leave disks 10% full? To get rid of the minimum of 2 disks per server you need to boot from SAN, and disk space in the SAN is often 10x the cost of standard SAS disks. Especially if the server could make do with the two built-in disks and save the cost of an FC card + FC switch port.
I/O's per second on the other hand cost real money, so it is a waste to leave 15k and SSD disks idle. A quarter full does not matter if they are I/O saturated; the rest of the capacity is just wasted, but again you often cannot buy a disk a quarter of the size with the same I/O's per second.
Finally! A year of moderation! Ready for 2019?
Having too much storage is an easy problem. Sure it cost a bit more, but not prohibitively so or you'd never have gotten approval to spend the money. Not having enough storage, OTOH, is a hard problem. Running out of space in the middle of a job means a crashed job and downtime to add more storage. That probably just cost more than having too much would've, and then you pile the political problems on top of that. So common sense says you don't provision for the storage you're going to normally need, you provision for the maximum storage you expect to need at any time plus a bit of padding just in case.
AT&T discovered this back in the days when telephone operators actually got a lot of work. They found that phone calls tend to come in in clumps, they weren't evenly distributed, so when they staffed for the average call rate they ended up failing to meet their answer times on a very large fraction of their calls. They had to change to staffing for the peak number of simultaneous calls, and accept the idle operators as a cost of being able to meet those peaks.
This is the CYA approach, and I don't see it getting any better. When configuring a server, it's usually better to pay the marginally higher cost for 3-4x as much disk space as you think you'll need, rather than risk the possibility of returning to your boss asking to buy MORE space later.
"People who think they know everything are very annoying to those of us who do."-Mark Twain
And "human resources"
"I'll go build my own data center, with blackjack and hookers!"?
There are two numbers that matter for storage systems. One is the raw number of gigabytes that can be stored. The other is the number of IO's that can be performed in a second. The first limits the size of the collected data. The second limits how many new transactions can be processed per time period. That, in turn, determines how many pennies we can accept from our customers during a busy hour.
We size our systems to hit performance targets that are set in terms of transactions per second, not just gigabytes. Using round numbers, if a disk model can do 1000 IO/second, and we need 10,000 IO/second for a particular table, then we need at least 10 disks for that table (not counting mirrors). We often use the smallest disks we can buy, because we don't need the extra gigs. If the data volume doesn't ever fill up the gigabyte capacity of the disks, that's ok. Whenever the system uses all of the available IO's-per-second, we think about adding more disks.
Occasionally a new SA doesn't understand this, sees a bunch of "empty" space in a subsystem, and configures something to use that space. When that happens, we then have to scramble, as the problem is not usually discovered until the next busy day.
Most SAN administrators wouldn't be caught dead using your $130 1TB drives. Rerunning your calculations with 15K 450GB SAS drives (around $300 bucks), and you're spending quite a bit more: 228 drives will give you 100TB, sure, but we'd want some redundancy . . . say RAID 5 (not the best approach for SAN design, but let's keep it simple) which pushes the drive count up to 304 with a total cost of $91,200, just for disks. To get a real, enterprise enclosure (or rather, cluster of enclosures considering the drive count) that offers things like FiberChannel, 10Gb iSCSI, or InfiniBand uplinks, and features such as SAN to SAN replication, bit deduplification, and other enterprise-level utilities/features, I'd say you're looking at $500,000 (ballpark guess) just to have something to stick the drives into. We're at ~$600,000 without even taking into account the physical costs of operation, datacenter architecture, or labor costs to maintain such a SAN.
Suddenly, that $1 million isn't so far fetched, eh?