Question 512n versus 512e sector drives

[a Michael]

Using a LSI MegaRAID 9260 controller which is better performance-wise, a 512n or 512e drive? Does the emulation needed for the 512n of going back and forth when it reads and writes between the 4k storage and the 512 logical block requests give a noticeable performance hit? One would think so.

 

[mv2devnull]

Are there not 512n, 512e, and 4Kn?
512n has 512 byte physical sectors. 512e and 4Kn have 4k physical sectors.
512n and 512e have 512 byte logical sectors. 4Kn has 4k logical sectors.

4k physical sector has some advantages over 512 byte sectors.

Filesystem typically has 4k blocks. With 4Kn that has 1:1:1 match.
With 512n that has 1:8:8 match. Does the filesystem send its 4k transaction as 8 separate disk accesses?
With 512e that has 1:8:1 match, unless there is misalignment.
Both 512n and 512e have thus filesystem sending 4k to eight 512 byte logical blocks.

 

[razel]

In addition 512 bytes is old. 4k is new. Choose whichever size is native to the drive.

 

[a Michael]

I understand the basics. I remember when the transition to 4k began quite some time ago. But my RAID card only supports 512 sectors either natively or through emulation. And as I understand how the emulation works it seems pretty taxing even if it all happens in memory.
I understand the advantages of 4k and my other computer is using 4k but it does not have a RAID card either. I thus far love my 9260 having only a SSD on one channel and am blown away by the performance compared to just running on normal SATA 6G. I want to RAID my data drive in RAID 5 or 6 (if I get a good deal on the drives).
I have not yet purchased the drives and that is why I was asking. I am using Windows 7 and shall not be giving into Windows 10 on this computer.
I do want 15k drives and I need to choose between the HGST (512n) and the Seagates(512e). The Seagates have better cache but my experiences with their consumer drives has never been good. Apparently the HGSTs are built by Western Digital so that is reassuring (although I am not sure if all the SAS ones are).

 

[razel]

Why not test it yourself and let us know. That's what we HDD nerds would do.

 

[a Michael]

Money, money, money. I wish I could just purchase several of each (512, 512e, 4kn) and arrive at a definitive answer. Because of my lack of disposable funds I reached out into this pool of acquired knowledge.
My suspicions are that being that LSI published an extensive list of "qualified" drives (updated in November 2015, well after the widespread adaption of 4k drives) and their specs with no 4k drives listed; and then trying to understand the procedure of emulation that 512n are the best suited. But I did want to understand if any difference was noticeable at all, being that it all happened in memory (but those extra steps do sound huge to me).
I am hoping that a drive guru will see this post and respond with illuminating information. I am looking for the best and most stable performance. Afterall that is why I want a 15k SAS drive.

 

[thecoolnessrune]

I will say that there is almost zero use case for a consumer to have a 15K Drive. 15K disks at this point serve two purposes.

1. Support the continued operation of old Enterprise Storage Arrays that don't have code supporting Flash.
2. Provide an artificial product tiering in the enterprise market that justifies the continued high prices of enterprise flash (if the only thing that existed was 7.2K Spinning Rust, and SSD, All-Flash would be price compressed down-market competing with itself. 10K and 15K disks help support higher pricing in Enterprise Markets for All-Flash).

A consumer does not have to generally worry about staying with an ancient hardware investment, nor do they need to worry about balancing a large array, or maintaining consistent deployment.

The reason your 9260 may feel fast is likely due to the RAM Cache in play that soaks up writes. It was of course originally provided to make up for the lack of IOPS performance from spinning disk, including 10K and 15K disks.

A 900GB 15K disk might cost you $90 on the used market. In RAID 6 with 4 disks you're managing You're managing about 1.8TB of disk space, numerous components to fail, a lot of power and heat, and still spending $350 on the endeavor. For $200 you can buy 1.92TB Enterprise SSDs with extremely linear latency, power loss protection, and performance characteristics from a single SSD that would put a 9260-8i with 8 15K disks to shame. That's why there's a bunch of them on the used market from EMC and the like using them as Flash Cache for their Storage arrays in front of whole shelves worth of disks.

As to the 512 vs. 4K thing. There is no performance disadvantage to 512e over 512n. None. The problem with 512e is that some systems won't read the "emulated" part right, and will still detect the disk as a 4K disk it can't use, rather than the 512e sector size. VMware was awful about this all the way to just a couple of 3 ago when they finally brought 512e support to 6.5, and only 2 years ago for 4kN support with 6.7. You have an old Gen 2 LSI Card, so it doesn't support 4K at all. 512n is the safest bet to use with that old card, however 512e is supported as long as you're on the MegaRAID 4.8 Firmware or higher.

For validation, see the Broadcom KB on the subject: https://www.broadcom.com/support/kn...212.235523697.1586918084-415429152.1586918084

But again, an SSD would make way more sense here over 15K disks, and those old Enterprise SSDs all support either 512n or 512e due to having to work in the same environments as your old LSI card.

 

[a Michael]

I will say that there is almost zero use case for a consumer to have a 15K Drive. 15K disks at this point serve two purposes.

1. Support the continued operation of old Enterprise Storage Arrays that don't have code supporting Flash.
2. Provide an artificial product tiering in the enterprise market that justifies the continued high prices of enterprise flash (if the only thing that existed was 7.2K Spinning Rust, and SSD, All-Flash would be price compressed down-market competing with itself. 10K and 15K disks help support higher pricing in Enterprise Markets for All-Flash).

A consumer does not have to generally worry about staying with an ancient hardware investment, nor do they need to worry about balancing a large array, or maintaining consistent deployment.

The reason your 9260 may feel fast is likely due to the RAM Cache in play that soaks up writes. It was of course originally provided to make up for the lack of IOPS performance from spinning disk, including 10K and 15K disks.

A 900GB 15K disk might cost you $90 on the used market. In RAID 6 with 4 disks you're managing You're managing about 1.8TB of disk space, numerous components to fail, a lot of power and heat, and still spending $350 on the endeavor. For $200 you can buy 1.92TB Enterprise SSDs with extremely linear latency, power loss protection, and performance characteristics from a single SSD that would put a 9260-8i with 8 15K disks to shame. That's why there's a bunch of them on the used market from EMC and the like using them as Flash Cache for their Storage arrays in front of whole shelves worth of disks.

As to the 512 vs. 4K thing. There is no performance disadvantage to 512e over 512n. None. The problem with 512e is that some systems won't read the "emulated" part right, and will still detect the disk as a 4K disk it can't use, rather than the 512e sector size. VMware was awful about this all the way to just a couple of 3 ago when they finally brought 512e support to 6.5, and only 2 years ago for 4kN support with 6.7. You have an old Gen 2 LSI Card, so it doesn't support 4K at all. 512n is the safest bet to use with that old card, however 512e is supported as long as you're on the MegaRAID 4.8 Firmware or higher.

For validation, see the Broadcom KB on the subject: https://www.broadcom.com/support/kn...212.235523697.1586918084-415429152.1586918084

But again, an SSD would make way more sense here over 15K disks, and those old Enterprise SSDs all support either 512n or 512e due to having to work in the same environments as your old LSI card.

I will say that there is almost zero use case for a consumer to have a 15K Drive. 15K disks at this point serve two purposes.

1. Support the continued operation of old Enterprise Storage Arrays that don't have code supporting Flash.
2. Provide an artificial product tiering in the enterprise market that justifies the continued high prices of enterprise flash (if the only thing that existed was 7.2K Spinning Rust, and SSD, All-Flash would be price compressed down-market competing with itself. 10K and 15K disks help support higher pricing in Enterprise Markets for All-Flash).

A consumer does not have to generally worry about staying with an ancient hardware investment, nor do they need to worry about balancing a large array, or maintaining consistent deployment.

The reason your 9260 may feel fast is likely due to the RAM Cache in play that soaks up writes. It was of course originally provided to make up for the lack of IOPS performance from spinning disk, including 10K and 15K disks.

A 900GB 15K disk might cost you $90 on the used market. In RAID 6 with 4 disks you're managing You're managing about 1.8TB of disk space, numerous components to fail, a lot of power and heat, and still spending $350 on the endeavor. For $200 you can buy 1.92TB Enterprise SSDs with extremely linear latency, power loss protection, and performance characteristics from a single SSD that would put a 9260-8i with 8 15K disks to shame. That's why there's a bunch of them on the used market from EMC and the like using them as Flash Cache for their Storage arrays in front of whole shelves worth of disks.

As to the 512 vs. 4K thing. There is no performance disadvantage to 512e over 512n. None. The problem with 512e is that some systems won't read the "emulated" part right, and will still detect the disk as a 4K disk it can't use, rather than the 512e sector size. VMware was awful about this all the way to just a couple of 3 ago when they finally brought 512e support to 6.5, and only 2 years ago for 4kN support with 6.7. You have an old Gen 2 LSI Card, so it doesn't support 4K at all. 512n is the safest bet to use with that old card, however 512e is supported as long as you're on the MegaRAID 4.8 Firmware or higher.

For validation, see the Broadcom KB on the subject: https://www.broadcom.com/support/kn...212.235523697.1586918084-415429152.1586918084

But again, an SSD would make way more sense here over 15K disks, and those old Enterprise SSDs all support either 512n or 512e due to having to work in the same environments as your old LSI card.

I appreciate you feedback and I am sure that 15k drives are partially responsible for helping to keep SAS SSDs at an inflated price.

I will say that there is almost zero use case for a consumer to have a 15K Drive. 15K disks at this point serve two purposes.

1. Support the continued operation of old Enterprise Storage Arrays that don't have code supporting Flash.
2. Provide an artificial product tiering in the enterprise market that justifies the continued high prices of enterprise flash (if the only thing that existed was 7.2K Spinning Rust, and SSD, All-Flash would be price compressed down-market competing with itself. 10K and 15K disks help support higher pricing in Enterprise Markets for All-Flash).

A consumer does not have to generally worry about staying with an ancient hardware investment, nor do they need to worry about balancing a large array, or maintaining consistent deployment.

The reason your 9260 may feel fast is likely due to the RAM Cache in play that soaks up writes. It was of course originally provided to make up for the lack of IOPS performance from spinning disk, including 10K and 15K disks.

A 900GB 15K disk might cost you $90 on the used market. In RAID 6 with 4 disks you're managing You're managing about 1.8TB of disk space, numerous components to fail, a lot of power and heat, and still spending $350 on the endeavor. For $200 you can buy 1.92TB Enterprise SSDs with extremely linear latency, power loss protection, and performance characteristics from a single SSD that would put a 9260-8i with 8 15K disks to shame. That's why there's a bunch of them on the used market from EMC and the like using them as Flash Cache for their Storage arrays in front of whole shelves worth of disks.

As to the 512 vs. 4K thing. There is no performance disadvantage to 512e over 512n. None. The problem with 512e is that some systems won't read the "emulated" part right, and will still detect the disk as a 4K disk it can't use, rather than the 512e sector size. VMware was awful about this all the way to just a couple of 3 ago when they finally brought 512e support to 6.5, and only 2 years ago for 4kN support with 6.7. You have an old Gen 2 LSI Card, so it doesn't support 4K at all. 512n is the safest bet to use with that old card, however 512e is supported as long as you're on the MegaRAID 4.8 Firmware or higher.

For validation, see the Broadcom KB on the subject: https://www.broadcom.com/support/kn...212.235523697.1586918084-415429152.1586918084

But again, an SSD would make way more sense here over 15K disks, and those old Enterprise SSDs all support either 512n or 512e due to having to work in the same environments as your old LSI card.

I appreciate your feedback and I do agree that 15k drives and many other "choices" do help to inflate prices. Enterprise SSDs are way expensive and a used one is concerning especially since I have experienced what happens when a "high quality" consumer grade SSD suddenly just dies without warning. With a hard drive there is usually warning, plenty of warning. I have never had advanced warning signs when a SSD was going to die (and they just die...no nothing). I have had 2 Crucials and a Corsair SSD just die in my non-workstation box. No other drives affected not even when on the same controller. So, I am gun shy. I know there is a vast difference between high end consumer SSDs and enterprise SSDs. But considering the costs....
I am a hobbyist, lets say. For like 20 years I had always wanted a WD Velociraptor just to see how good they really were. So I am enticed to see how much performance can be gotten with 6G SAS 15k on my RAID card. For my humble system (an old refurbished Lenovo 1366 D20 which I added the 2nd Xeon and then replaced them with 6-core Xeons, added a bunch of memory and finally this old LSI 9260 card after living with those SATA III add-in cards on both of my computers) it is time to see where this box could have been when it was new. You know, state of the art for 2013 or whatever.
So, the world seems to agree that, performance wise, that 512n and 512e are pretty much the same. And I do agree with your point of the native 512 being the safer choice. I know in one of my posts I swapped the 512n and 512e around, I have just been somewhat leery as to a 512e being an equal choice. And I am now committed to getting a 512n 15k SAS HD. I think my little heart is set on it. I am sure that later on down the road I will experiment with a small SSD array.
And yes I am going to use a SSD as a cache drive for my RAID 6 or 5. I do like the idea of perhaps doing a RAID 5 initially and then adding a drive or two and then having it convert to a RAID 6 (that is such a cool feature).