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SMR?RESILVER?

tfran1990

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#1
I replaced a hdd in my freenas, but i have noticed that the disk is showing Deletes in Disk operations and Disk latency. The disk i replaced was a 7200rpm HGST 2TB 64m cache with a new WD blue 2TB 5400rpm 256m cache.(its blue i know, but it was 40$ new with warranty on newegg)

Before i replaced the drive i did a smartctl short and long, then the 3 pass badblocks on the drive followed by a long. could the drive be deleting the dummy test data?

Maybe this is an SMR disc, but i wouldnt think that WD would make a 2TB SMR. i looked online to try to find out if it is or is not.

The replacement went seamless, no problems what so ever.
Its just odd to me because the 5 discs i put into my freenas at first never reported any deletes.

can someone help me understand why this is?

diskIO.PNG
Disklat.PNG
 
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Chris Moore

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#2
What is the model number of that new drive? We might be able to look it up.
 

HoneyBadger

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#3
I'm going to guess WD20EZAZ, which is a single 2TB SMR platter based on my research.

The huge amounts of cache (256MB) is almost a dead giveaway these days for "shingled platters within" - unfortunately the manufacturers are refusing to indicate it clearly.
 

tfran1990

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#4
ya its a WD20EZAZ. f* i was trying to avoid SMR discs.

i picked up 3 of them.....
i can still return them.....
even with just one it shouldn't dampen performance too much?
 
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Chris Moore

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#5
ya its a WD20EZAZ. f* i was trying to avoid SMR discs.

i picked up 3 of them.....
i can still return them.....
even with just one it shouldn't dampen performance too much?
None of the drives are what they once were. All the manufacturers are trying to improve profit margins everywhere they can because they are really feeling the pressure from SSDs pushing into what used to be the mechanical drive space. It is very hard to sell mechanical drives for $100, when SSDs are as cheap as they are.
 

Chris Moore

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#8

Johnnie Black

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#12
Well, technically the disks are still PMR (with SMR), they usually now refer to non SMR disks as CMR (conventional magnetic recording), but IMHO there's no way those disks aren't SMR, they use a single 2TB platter and those are not possible without SMR, see for example here:

https://www.anandtech.com/show/1466...-10-tb-hdd-for-enterprises-w-40-faster-writes

The Ultrastar DC HC330 10 TB air-filled hard drives rely on six 1.66-TB CMR platters (the highest-capacity commercially available platters in the industry today), down from seven 1.42 TB PMR disks in case of the helium-filled Ultrastar He10.

You might say, maybe it uses more than one platter, I'll point out that the 567g weight points to a single platter, and also the old 2TB disk was already a 2 platter design (two 1TB platters), it wouldn't make any sense to release a new 2 TB disk with say two 1.5/1.6TB platters, if it was a 2 platter 3TB disk sure.
 
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tfran1990

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#13
WD is trying to be sneaky here.
The points you have made are valid.

With 256mb cache ,5400rpm im interested to know more about how the performance compare to a PMR 7200.
I see the reads will be good speed and writes not so much, but i am questioning latency. As shown above, sometimes i see big latency spikes. Are the spikes due to cache being full?

Was WD intention to make a product that is the same performance, or were they just trying to use smr platters spinning at 5400 then throw a crap load of cache as a last resort to try to get somewhat close to the performance consumers will accept?
 

Johnnie Black

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#14
For non raid usage these disks should perform better than the equivalent old model, since the higher platter density will result in higher sequential speeds, about the same as the existing 2TB 7.2k CMR disks, which is around 200MB/s on the outer sectors, vs 150MB/s for the old 2TB Blue/Red, and I have no problem with WD releasing these on the Blue line, I do question releasing them also on the Red line, where they can be used on various types of raid, and where it's more more likely the user will hit the SMR wall.

They are always trying to improve SMR performance with more cache and a more advanced firmware, and I never tested these with FreeNAS, I did test older SMR models and most notably the resilver performance was terrible, taking for example 3 days instead of 15 hours on my server, but maybe these new disks work better, I would still try to avoid them for any kind of raid, at least until there is more user data on them.
 

Johnnie Black

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#16
when i put the 1 in my server it took maybe 20 min to resilver 580G on a 5X2TB vdev.
Unlike the FreeNAS release I used at the time I believe the current does a more sequential resilver, so that could make a difference, also my resilver was much more data on 4TB disks, still that's good news.
 

tfran1990

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#17
What do you think would be the best way to get a bench mark for this disk?
i have seen some people use dd and iostat(can't remember exactly)to do a performance test.
 

Johnnie Black

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#18
What do you think would be the best way to get a bench mark for this disk?
Sorry, don't really know of a good way to test with FreeNAS, the way I noticed mine were underperforming was during the resilvers and when doing a large transfer, the SMR disks kept up for a few GBs, as they usually have a small PMR zone, then it would slow down the transfer, and looking at the FreeNAS stats I could see they were at 100% use while the other disks were at 40/60%.
 

tfran1990

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#19
were at 100% use while the other disks were at 40/60%.
Its not uncommon during a resilver the disc being written to will run higher % used(maybe 50%) the rest that are reading do like 25%. Its going to take time to see how the SMR discs playout.
It might not be a bad thing if using smr drives the price down a lot. less heat. longer life span. less noise. higher density, could it be be worth it?
 
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