Hi, I am buying Seagate’s 30TB Exos M. It is shipped with a sector type of 512e. I am about to create a new pool with it.
Here on, please correct me if I am mistaken. I would really appreciate it. The zpool created will be ashift=12, and to my understanding, the performance difference for 4Kn and 512e will be negligible. So the question is that should I actually FastFormat my 30TB Exos M Firmware to make it 4Kn, or would the hassle not provide any noticeable performance improvement at all? I can’t find much discussion regarding this so far so I would like to start it.
In short, is 4Kn better than 512e? And if the drive is default 512e, should I update the firmware to make it 4Kn? (30TB Exos M for my case)
I would do it, but it probably will not make much of a difference.
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Yea. I thought so too. I am not sure if this will void any warranty or anything, but it is in the manual, so should be fine. Just wondering if it worth the hassle. And not much discussion on this as well. So, just trying to get it out there.
Hmm… does it announce itself as 512e by default though?
If I am not mistaken, TrueNAS will use the ashift number based on what the drive announces. So that would mean that while the drive does support 512e (emulated) it comes with 4k by default.
That is a really interesting question. Since the drive uses 4k native (?) and 512e emulated, what would FastFormat TM actually do? Just change what sector size the drive announces itself to the OS? So in this case it would probably change nothing?
Drives that size using 512e seems unusual. Is there a software utility that will change the drives sector type to 4kn.
It will make a positive difference because internally it is using 4k sectors and then translating them to 512 sectors which takes processing, however little. (512e)
Not all drives all you to change sector sizes.
Internal sector size and that presented to the system are different. 512e is a mode that allows drives to work with older systems that cannot handle 4k sectors.
I am not an expert and these are expensive drives 
The zshift will be the same for both of these settings.
Seagate shipped it as 512e. You can see it in their official spec too. However, it is natively 4K and 512 emulated, as what the “e” stands for. I reckon it is shipped as 512e, for this is an enterprise drive and the backward compatibility is a huge plus for legacy systems in industries that are still widespread.
And yes, the sector size exponent, “ashift” will be based on how the drive announces itself, but both 512e and 4Kn will be ashift=12. So my question is mainly on the performance difference between the two. Is it even significant at all to warrant the hassle?
You can use Seagate’s SeaChest tools, specifically SeaChestLite, which supports the Fast Format feature. The native sector size is fixed from manufacturing to my understanding, it is just the way it announces itself, the sector type or sector format like 512e, 512n, 4Kn, etc. is on the firmware if my understanding is correct.
P.S. Please fact-check me. I would love to learn from the community as well.
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It is set in the firmware, but a lot of drives allow you to change the sector size exposed to the system. I think some drive types even let you change the internal sector size but it has been a while since I looked into this, might be a SAS thing.
Sure?
I think ashift 12 = 4k and ashift 9 = 512
Can say for my HC550. Max sequential speed increased from ~270MB/s to ~285MB/s. Tested for a single drive with HD Tune. Perhaps it isn’t worth it.
I’m planning to perform the transition for my main pool. The main reason is testing the restore process.
I do it for every Exos I get. I use SeaChest. There’s no data to lose because they are brand new drives.
While you are using SeaChest, I recommend that you disable the EPC timers.
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Seagate does not ship different model numbers for 512e or “native” 4k: Drives support both sector sizes; change from the default 512e is a simple operation from Seagate’s utilities. (And a trip there is required to disable head parking, so why not throw 4k?)
TrueNAS defaults to ashift=12 anyway.
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For SAS drives using the sg_format command from within TN is probably the easiest route.
sg_format --format --ffmt=1 --size=4096 /dev/sda
The --ffmt=1 option takes a process that may take many hours (depending on the size of your drives) and turns it into seconds.
HI, Thanks for the info. Would you be kind to explain on the EPC timer? I would really appreciate it.
for 512e, it is still a physical 4K drive
Let me reiterate, by the EPC timer, I mean to ask on how much significant performance you get from it and also the impact to the drive’s longetivity.
Hi, what do you mean by this line
Blockquote (And a trip there is required to disable head parking, so why not throw 4k?)
Same as @winnielinnie with “EPC”: Seagate drives default to aggressively park their heads.
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Just as @etorix said. Without disabling them, the drives will want to aggressively park their heads. Not only is this extra wear and not practical for a 24/7 NAS, but it can cause minor delays, depending on your workflow.
The reason you have to disable their EPC timers is because they ignore the advanced power settings in the TrueNAS GUI and from hdparm.
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Thanks. Really appreciate the details.