WD20EARS - smartctl is reporting 4K physical sector size ^^

Orangutanklaus · 09-18-2011, 04:56 AM

Hiho,

I'm running a raid5 with 3 WD20EARS hard disk drives. These days I bought 2 new drives to expand the current raid set. To eleminate problems during raid builds I always test new drives for errors. When I checked the SMART status I noticed by the way that the new drives report a physical sector size of 4096.

Strange, because the old and new HDDs have the same firmware version installed while the old ones still report a physical sector size of 512 (what's wrong as we know). I guess Western Digital has updated the firmware without changing the firmware number but other explanations are welcome.

This leads to my question. Does it have any impact of the handling from the kernel side or ist this just nice to know that the hard disk drives are reporting the correct physical sector size?

Regards
OK

salasi · 09-18-2011, 01:57 PM

Quote:

Originally Posted by Orangutanklaus

Strange, because the old and new HDDs have the same firmware version installed while the old ones still report a physical sector size of 512 (what's wrong as we know). I guess Western Digital has updated the firmware without changing the firmware number but other explanations are welcome.

What I remember of drives of this generation is that there was a jumper setting to choose between the drives 'native' 4096 and 'emulated' 512 byte settings. So, if this applies to the drives that you have, the first thing to do is to check the settings of any jumpers.

When you say "what's wrong as we know", then that isn't entirely true; if the drive is successfully emulating a 512 byte size, then, from the point of view of software, it looks exactly like a 512 byte drive, so when you ask the software what size the drive is, it isn't entirely incorrect of it reports that the size is 512. Well, the performance would be different, of course...

cascade9 · 09-19-2011, 06:30 AM

Nah, there is no jumper to cheange from 512b to 4K on the EARS drives.

As for why your new drives apear as 4k in SMART, it could be due to SMART upates. But if the older drives apearas 512b drives still thats not likely....

BTW, you do know that the 'green power' drives are not recommended for RAID arrays?

Quote:

Originally Posted by salasi

When you say "what's wrong as we know", then that isn't entirely true; if the drive is successfully emulating a 512 byte size, then, from the point of view of software, it looks exactly like a 512 byte drive, so when you ask the software what size the drive is, it isn't entirely incorrect of it reports that the size is 512. Well, the performance would be different, of course...

512b 'emulation' can cause partion alingment problems. If the drives correctly reported as 4K drives to OSes/tools that 'know' about 4K sectors, alignment is not a problem.

salasi · 09-19-2011, 09:36 AM

Err, yes, the jumper only offsets by one, it is the align tool that gets closer to 4k emulation. So, I guess, it more closely depends on whether anyone has run the align software tool or the default firmware align state from WD has changed.