Harddrive Write Cache Disabled.

[joshuah]

Hi,


I just updated my 212J to 4.0 and I noticed the following messages in dmesg:


sd 0:0:0:0: [sda] Write cache: disabled, read cache: enabled, doesn't support DPO or FUA
sd 1:0:0:0: [sdb] Write cache: disabled, read cache: enabled, doesn't support DPO or FUA

If i try to enable it from the "HDD Management", I get the following errors in dmesg:


ata1.00: skip command 0xef feature 0x2
ata2.00: skip command 0xef feature 0x2

Both drives had this feature enabled in 3.2 and It was all fine both Drives are WD20EARX 2TB.

[sanderdw]

I have the same problem with a WD10EADS and WD10EACS on a DS212+.

[006fazer]

Hi

Same problem for me, with my DS210j and two WD15EARS

[jipy]

Hi,

Same issue here with the WD20EARX disks (2TB) on my DS212

the UI says "system successfully enabled disk write cache"

but write cache is not enabled (box still unchecked in the UI).

I also have those messages in /var/log/messages :

Mar 7 19:10:30 kernel: [ 516.800000] ata1.00: skip command 0xef feature 0x2
Mar 7 19:10:40 kernel: [ 516.800000] ata2.00: skip command 0xef feature 0x2

Cheers

Jipy

[joshuah]

Just to note that in 4.0-2198 this issue is still NOT fixed. I just hope synology is watching this forum, and is aware of the issue. I can assume that write cache disabled can have pretty decent performance impact on the NAS when doing writes.

[HarryPotter]

I just hope synology is watching this forum, and is aware of the issue

No, they are not. If you want to report an issue, please submit a support form

[joshuah]

I did open a support form for this issue, and would like to ask whoever has this issue to open a support form so it can be fixed faster. Thanks in advance.

[crhiles]

Looking in /usr/syno/etc.defaults/scemd.xml it appears they added some code to disable write cache on specific drive models. So this appears to be a feature and not a bug.

Code: Select all

<disk_control>
   <disk model="ST9120821A">APM_255</disk>
   <disk model="HTS722020K9SA00">APM_255</disk>
   <disk model="ST980811AS">APM_255</disk>
   <disk model="MHV2060BH">APM_255</disk>
   <disk model="MK6034GSX">APM_254</disk>
   <disk model="ST9100824AS">APM_255</disk>
   <disk model="HM250JI">APM_255</disk>
   <disk model="MK1637GSX">APM_254</disk>
   <disk model="ST9100824AS">APM_255</disk>
   <disk model="ST9120822AS">APM_254</disk>
   <disk model="ST9160821AS">APM_254</disk>
   <disk model="WD2500BEVS-75UST0">APM_254</disk>
   <disk model="HM250JI">APM_254</disk>
   <disk model="WD2500BEVS">APM_254</disk>
   <disk model="WD1600BEVT">APM_255</disk>
   <disk model="HTS543232L9A300">APM_255</disk>
   <disk model="WD1600BEVE">APM_255</disk>
   <disk model="MK2546GSX">APM_254</disk>
   <disk model="MHV2080BHPL">APM_255</disk>
   <disk model="WD1200BEVE">APM_255</disk>
   <disk model="HTS543225L9A300">APM_255</disk>
   <disk model="WD3200BEVT">APM_254</disk>
   <disk model="MK8025GAS">APM_254</disk>
   <disk model="ST9200420AS">APM_254</disk>
   <disk model="WD3200BEVT">APM_254</disk>
   <disk model="HTS543216L9SA00">APM_254</disk>
   <disk model="MK4058GSX">APM_254</disk>
   <disk model="WD6400BEVT">APM_254</disk>
   <disk model="ST32000542AS">APM_255</disk>
   <disk model="ST95005620AS">APM_255</disk>
   <disk model="WD7500BPVT">APM_254</disk>
   <disk model="WD30EZRX">WCACHE_OFF</disk>
   <disk model="WD25EZRX">WCACHE_OFF</disk>
   <disk model="WD20EARX">WCACHE_OFF</disk>
   <disk model="WD15EARX">WCACHE_OFF</disk>
   <disk model="WD10EADX">WCACHE_OFF</disk>
   <disk model="WD7500AARX">WCACHE_OFF</disk>
   <disk model="WD30EZRSDTL">WCACHE_OFF</disk>
   <disk model="WD25EZRSDTL">WCACHE_OFF</disk>
   <disk model="WD20EARS">WCACHE_OFF</disk>
   <disk model="WD15EARS">WCACHE_OFF</disk>
   <disk model="WD10EARS">WCACHE_OFF</disk>
   <disk model="WD8000AARS">WCACHE_OFF</disk>
   <disk model="WD7500AARS">WCACHE_OFF</disk>
   <disk model="WD6400AARS">WCACHE_OFF</disk>
   <disk model="WD20EADS">WCACHE_OFF</disk>
   <disk model="WD15EADS">WCACHE_OFF</disk>
   <disk model="WD10EADS">WCACHE_OFF</disk>
   <disk model="WD8088AADS">WCACHE_OFF</disk>
   <disk model="WD7500AADS">WCACHE_OFF</disk>
   <disk model="WD6400AADS">WCACHE_OFF</disk>
   <disk model="WD5000AADS">WCACHE_OFF</disk>
   <disk model="WD3200AACS">WCACHE_OFF</disk>
   <disk model="ST32000542AS">WCACHE_OFF</disk>
   <disk model="ST31500541AS">WCACHE_OFF</disk>
   <disk model="ST31000520AS">WCACHE_OFF</disk>
   <disk model="ST3500412AS">WCACHE_OFF</disk>
</disk_control>

[joshuah]

This "Feature" was not present in 3.2 and all worked fine. And having write cache disabled can have severe performance implications on the hard drives and the NAS, when you consider that some drives have 64MB of cache per drive.

[jipy]

This "Feature" was not present in 3.2 and all worked fine. And having write cache disabled can have severe performance implications on the hard drives and the NAS, when you consider that some drives have 64MB of cache per drive.

I agree, an I just opened a support ticket for this issue too.

Jipy

[Metrik]

Having two WD20EARX's in my 212j, I opened a ticket on the issue as well.

[sanderdw]

I got feedback from Synology Support. Apparently it is indeed a 'feature'.

For certain HDD like Caviar green HDD, the write cache is not being supported on DS on DSM4.0.

Sorry for the inconvenience caused.

Thank you.

Best Regards
Jim Cheng

I asked him, if this 'feature' is decreasing any performance. When i hear from him again, i'll report here.

[joshuah]

Wow...nice to see that they mentioned this "small" detail, in the release notes of 4.0. It is supported in 3.2 but not in 4.0...talk about going back...
In the Harddrive support list there is/was no mention of this "small" detail, and people bought these drives because they were FULLY supported, and now they find out that they can't use the hard drive cache for write ( in my case 64MB ), which probably has pretty big impact on the performance...
I will be very disappointed if this issue isn't handled properly, having these drives with write cache unsupported is completely unacceptable , and saying "sorry" isn't going to cut it .

[jekyll]

I will be very disappointed if this issue isn't handled properly, having these drives with write cache unsupported is completely unacceptable , and saying "sorry" isn't going to cut it .

+1 for me...

I've 4 WD greens in the DS410. I've multiple cams recorded by the unit and it also serves DLNA... So It's under demand.

I chose WD Greens due to the cost of power in the UK, I've 13 drives in 4 Synology units.. So power needs to be kept to a minimum!

[Hanzoy]

I got feedback from Synology Support. Apparently it is indeed a 'feature'.

For certain HDD like Caviar green HDD, the write cache is not being supported on DS on DSM4.0.

Sorry for the inconvenience caused.

Thank you.

Best Regards
Jim Cheng

I asked him, if this 'feature' is decreasing any performance. When i hear from him again, i'll report here.

Thanks. Would like to see what they have to say about decreasing in performance.