RAID Performance Calculators

DustinB3403

Can anyone think of a good tool that could be used free of charge?

Searching around there are a ton of paid solutions, but this seems rather excessive for the limited use we'd actually use it.

scottalanmiller

MB/s is not something you generally care about at all. It's IOPS that matter.

scottalanmiller

@DustinB3403 said:

But where would I find existing "Read operations percentage" ? This seems odd to calculate. I'm sure it has a logical reason for being there.

Because it changes significantly what the IOPS are based on the RAID level. You get generally quite different read and write performance, so knowing you read and write blend is necessary to know how many IOPS you will get from your setup.

scottalanmiller

@Dashrender said:

That Dell tool (was it called DMAC?) can do this. You have to run a utility on your system that watches for these types of things. It's not perfect, but you're only looking for a rough guess.

DPACK

Jason

@Dashrender said:

That Dell tool (was it called DMAC?) can do this. You have to run a utility on your system that watches for these types of things. It's not perfect, but you're only looking for a rough guess.

DPACK and it's not a calculator it runs on the system to calculate used IOPS.

scottalanmiller

@DustinB3403 said:

Does this mean: "What percentage of your access is people only reading something and then closing it?" And if so, how would I calculate this?

Sort of. It is "What percentage of IOPS are reading from storage versus writing to it."

Dashrender

@Jason said:

@Dashrender said:

That Dell tool (was it called DMAC?) can do this. You have to run a utility on your system that watches for these types of things. It's not perfect, but you're only looking for a rough guess.

DPACK and it's not a calculator it runs on the system to calculate used IOPS.

yep and it should be telling you how many for write vs how many for read... there's your percent.

StrongBad

You could use tools inside of the operating systems to determine the W/R mix on a per OS basis. Or similar, I suspect, in most hypervisors.

Reid Cooper

@DustinB3403 said:

Single disk performance: IO/s MB/s
Read performance: 540
Write performance: 520

Those numbers are very small for IOPS from SSDs. I would expect at least one hundred times those numbers. Maybe more.

donaldlandru

@Reid-Cooper said:

@DustinB3403 said:

Single disk performance: IO/s MB/s
Read performance: 540
Write performance: 520

Those numbers are very small for IOPS from SSDs. I would expect at least one hundred times those numbers. Maybe more.

Those numbers are the max r/w speed is MB/s not iops numbers, as @scottalanmiller pointed out above really don't matter in this question...

DustinB3403

So here's a link to the exact drive I'm looking at.

To save a few clicks

Performance
Max Sequential Read Up to 540 MBps

Max Sequential Write Up to 520 MBps

4KB Random Read
Random read (QD1) [IOPS]: up to 10,000 IOPS
Random read (QD32) [IOPS]: up to 98,000 IOPS

4KB Random Write
Random Write (QD1) [IOPS]: up to 40,000 IOPS
Random Write (QD32) [IOPS]: up to 90,000 IOPS

Dashrender

IOPs with SSD are so large in comparison to their HDD brethren, just one drive often beats an entire array of SAS 15K RAID 10 drives (8 drives @190 IOPs/drive = 1520 random read / 760 random write).

These are just simple ballparks.

DustinB3403

Yeah I did the math on the SSD drives above, and the rates IOPS is 4.4 GB/m.

Which there's no way SR (spinning rust) could keep up.

coliver

Can a SSD drive saturate the SATA connection they are attached to? Or are they not that fast yet.

I know most enterprises will probably start moving to PCIe SSD drives or at least a controller to integrate them.

DustinB3403

Well SATA supports up to 6GB/S

With my calculations I can push 4.4GB/m or 700MB/S (write)

So I don't think so.

coliver

@DustinB3403 said:

Well SATA supports up to 6GB/S

With my calculations I can push 4.4GB/m or 700MB/S (write)

So I don't think so.

Thanks.

Dashrender

@DustinB3403 said:

Well SATA supports up to 6GB/S

With my calculations I can push 4.4GB/m or 700MB/S (write)

So I don't think so.

Not a single drive. But an array definitely can.

DustinB3403

@Dashrender my calculations are a 12 disk RAID 5 array.

A bigger system might.

scottalanmiller

@DustinB3403 said:

Yeah I did the math on the SSD drives above, and the rates IOPS is 4.4 GB/m.

Drive performance is not measured in GB/m. It is measured in IOPS.

scottalanmiller

Looking at throughput numbers for drives is almost always useless. If you are building a streaming video server or a backup target that takes a single backup stream at a time, okay, there is a time where throughput can matter. But it is rare.

There is a reason why IOPS is the only number generally used when talking storage performance - because it is the only one of significance. It is only because of this that things like SANs have any hope of working as they have terribly slow throughput bottlenecks between them and the servers that they support. But most businesses can run from iSCSI over 1GigE wires. Why? Because it is the IOPS that matter, rarely the throughput.

If you look at throughput numbers, you will come up with some crazily dangerous comparisons that will lead you in some terrible decision making directions.