How to short stroke a hard drive in Disk Utility i.e. create 2 partitions, 1 unformatted

[tornado99]

Hi,

Short stroking a hard drive is creating two partitions and then only using the first one which is on the outer edge of the platter. This allows faster read/write speeds at the expense of storage space.

I want to divide my 2TB disk into a 1.5 TB HFS+ partion, and a 500GB unformatted space. Is there a way to do with Disk Utility or the command line? Obviously short stroking still works with the 500GB as HFS+ too, but it would be annoying for it to automount every time.

Disk Utility seems to want to force each partition to have a format.

 

[gilby101]

I am sure you can do what you want at the command line, though I have never done this.

First read man diskutil with particular reference to the partitionDisk verb. To paraphrase, it says that if you create n partitions (in your case 2), you must specify the format (as well as size and name) for each partition.

But it also says "You can specify a format of Free Space to skip an area of the disk". That would seem to be the way for you to proceed. I am guessing that Free Space needs to be written as "Free Space".

You can experiment with an empty disk so long as you make sure you reference the right disk!

Have you done tests to determine the appropriate short stroke size for your particular disk? I understand that this needs to be measured as it will vary depending on the architecture of the specific drive model.

 

[tornado99]

Thanks, very helpful. I will give that a go.

I did an experiment with 10 partitions on a 2 TB disk, and the speed dropped from 130mbps on the 1st to 60 mbps on the 10th. So it drops off across the disk in a close to linear fashion.

Actually I am not doing this to run an operating system, but for cold data storage that I will refer to occasionally.

 

[rpmurray]

Why not just use an SSD instead? Even the cheapest 2TB SSD would be faster than an HDD and the speed would be constant over the whole drive.

 

[joevt]

Thanks, very helpful. I will give that a go.

I did an experiment with 10 partitions on a 2 TB disk, and the speed dropped from 130mbps on the 1st to 60 mbps on the 10th. So it drops off across the disk in a close to linear fashion.

Actually I am not doing this to run an operating system, but for cold data storage that I will refer to occasionally.

Does cold data storage need to be accessed at more than 60 MB/s? I suppose if you ever full up a fast partition, you can always setup the next fastest partition.

You can try iPartition.app. It's unsupported but free. It can do anything except APFS. For APFS, you can use iPartition to create the partition as HFS+, then use Disk Utility.app to erase it as APFS. iPartition.app can add, delete, shrink, expand, and move partitions.

 

[tornado99]

Why not just use an SSD instead? Even the cheapest 2TB SSD would be faster than an HDD and the speed would be constant over the whole drive.

data corruption possible if left on a shelf for a few months. I like to mix data backup options, and on-site/offsite.

Does cold data storage need to be accessed at more than 60 MB/s? I suppose if you ever full up a fast partition, you can always setup the next fastest partition.

You can try iPartition.app. It's unsupported but free. It can do anything except APFS. For APFS, you can use iPartition to create the partition as HFS+, then use Disk Utility.app to erase it as APFS. iPartition.app can add, delete, shrink, expand, and move partitions.

Is iPartition a GUI for diskutil commands? Otherwise I am not sure how compatible it is with Ventura.

 

[Fishrrman]

Why does the "second" (unused) partition have to be un-formatted?
Why not create a second partition formatted HFS+... and then just leave it... "un-used"?

Or, perhaps just use it as "scratch space" -- store files on it that you rarely access and don't care if they're lost or not...?

 

[joevt]

Is iPartition a GUI for diskutil commands? Otherwise I am not sure how compatible it is with Ventura.

It seems to work fine in Ventura.

 

[tornado99]

Why does the "second" (unused) partition have to be un-formatted?
Why not create a second partition formatted HFS+... and then just leave it... "un-used"?

Or, perhaps just use it as "scratch space" -- store files on it that you rarely access and don't care if they're lost or not...?

It doesn't have to be. Performance is the same. It's just a bit more messy having it mounted each time.

Speed drops off to as low as 30 mbps I've seen on some modern hard drives at the centre of the platters. So short stroking definitely helps make HDDs at least a little more acceptable speed-wise.

 

[saudor]

don’t think it’s worth the trouble for something that goes into storage for months. for a modern 2tb drive, i’m betting that is using SMR platters so write speed will drop like a rock (e.g. a few MB per second) as soon as the CMR cache is filled and the drive starts thrashing to move the data onto the SMR tracks. (only 8tb WD or seagate 10tb and higher are guaranteed to be the traditional CMR drive everyone is used to)

 

[tornado99]

Yes it is SMR. Actually providing you use HFS+ and short-stroking, write speeds are very decent. I'm sure there might be spikes down to a few mbps but average speeds are higher than some older CMR drives I had. Remember SMR have higher density platters (1TB on a single platter) so the head needs to move less for reading the same amount of data as a CMR.

Also, if a SMR has been heavily used its best to wipe it and write zeros across the whole disk to trigger TRIM in the firmware. But for a backup with not too much file churn you might never need to do that.

 

[AndyMacAndMic]

data corruption possible if left on a shelf for a few months. I like to mix data backup options, and on-site/offsite.

Slightly off topic, but SSD data corruption after 'left on a shelf for a few months' is an unfounded assumption. What source did provide you with that information (if any)?

https://www.easeus.com/resource/does-ssd-need-power.html#:~:text=Overall, if SSD is not getting power for,power supply for around 15 to 20 years.

Quote from the link above:

Overall, if SSD is not getting power for several years, it may lose data. According to research, an SSD can retain your data for a minimum of 2-5 Years without any power supply. Some SSD manufacturers also claim that SSD can save data without a regular power supply for around 15 to 20 years.

 

[saudor]

Yes it is SMR. Actually providing you use HFS+ and short-stroking, write speeds are very decent. I'm sure there might be spikes down to a few mbps but average speeds are higher than some older CMR drives I had. Remember SMR have higher density platters (1TB on a single platter) so the head needs to move less for reading the same amount of data as a CMR.

Also, if a SMR has been heavily used its best to wipe it and write zeros across the whole disk to trigger TRIM in the firmware. But for a backup with not too much file churn you might never need to do that.

It's still a YMMV though and depends on what kind of files are being sent to it. The first write generally goes ok. Things go to hell when you start re-writing data - especially smaller ones - which is often the case with backups. More recent firmware are better masking the issues better but it's still there. For very large files it worked fine for me but as soon as I started writing smaller files like photos, the whole thing started struggling. This was with a 4TB drive which I presume has a larger CMR zone.

I also did a full erase and that also took a long time to run. At the end of the day, I was just spending more time messing around with "hacks" to get around the SMR issues so any perceived higher speeds from higher density was quickly lost. A 8TB CMR drive would likely run circles around a 2TB SMR even in the inner tracks and do so consistently.

If you truly must short stroke, I just partition it in windows, format the first NTFS partition to HFS in macOS (don't put any data yet), then remove the 2nd NTFS partition in Windows. Go back to macOS and make sure the remaining HFS is still readable. If it is, you're good to go.

 

[tornado99]

Slightly off topic, but SSD data corruption after 'left on a shelf for a few months' is an unfounded assumption. What source did provide you with that information (if any)?

https://www.easeus.com/resource/does-ssd-need-power.html#:~:text=Overall, if SSD is not getting power for,power supply for around 15 to 20 years.

Quote from the link above:

Overall, if SSD is not getting power for several years, it may lose data. According to research, an SSD can retain your data for a minimum of 2-5 Years without any power supply. Some SSD manufacturers also claim that SSD can save data without a regular power supply for around 15 to 20 years.

What I've read there doesn't seem to be a consensus on this topic. The manufacturers certainly aren't making any claims about cold storage. This in particular stood out:

SLC: effectively forever
MLC: a few years
TLC: a few months to a year
QLC: a month or so

The first write generally goes ok. Things go to hell when you start re-writing data - especially smaller ones - which is often the case with backups.

Ok well I guess I will have to see. TBH I invested in a couple of 2TB portable external HDDs before I knew about the SMR/CMR issue. So I'm just trying to make the best of what I already have.

 

[HDFan]

What source did provide you with that information (if any)?

Reliability is certainly improving, but there are lots of sources discussing cell leakage and the unreliability of long term SSD storage, including Wikipedia. The article you quoted mentions 2-5 years. I wouldn't trust the longer manufacturer numbers as of yet.

Here's one report of problems occurring after 3 years:

Question - How long to plug in an SSD to ensure data retention?

How long does an SSD have to be powered on to refresh/recharge it to prevent data loss due to cell leakage? (Note that I'm not asking how often). If the time needed to rejuvenate the cells could be precisely measured, I suppose, as with any other product, it would vary between brand, model and...

forums.tomshardware.com

 

[AndyMacAndMic]

Reliability is certainly improving, but there are lots of sources discussing cell leakage and the unreliability of long term SSD storage, including Wikipedia. The article you quoted mentions 2-5 years. I wouldn't trust the longer manufacturer numbers as of yet.

Here's one report of problems occurring after 3 years:

Question - How long to plug in an SSD to ensure data retention?

How long does an SSD have to be powered on to refresh/recharge it to prevent data loss due to cell leakage? (Note that I'm not asking how often). If the time needed to rejuvenate the cells could be precisely measured, I suppose, as with any other product, it would vary between brand, model and...

forums.tomshardware.com

Thanks for the info. I agree with you that the longer manufacturer numbers have to be taken with a grain of salt.
Your link is to a forum with a post claiming data corruption of some files after >3 years (which falls within the 2-5 years expectation), but the OP claims data corruption after 'a month or a view months'. I have never seen/heard that before. Also I could not find sources about the OP's claim.

 

[AndyMacAndMic]

TLC: a few months to a year
QLC: a month or so

As I asked before, can you provide a source/link to these? I have never seen values of months in all the information I have encountered about SSDs. From what I understand the general consensus is 2-5 years without power (also for TLC and QLC assuming the SSD is stored under normal circumstances/temperatures).