is ashift=12 recommended for 3TB WD Green drives?

Moderators: jhartley, MSR734, nola

is ashift=12 recommended for 3TB WD Green drives?

Post by markpaterson » Fri Oct 05, 2012 2:09 pm

I have a Mac Pro, 32GB Ram, with 3x 3TB WD Green drives in a RaidZ pool.

I used the following command to create the pool…

Code: Select all
sudo zpool create -O casesensitivity=insensitive Ocean raidz /dev/disk1 /dev/disk2 /dev/disk3


After some further perusing of this forum, it's occured to me that maybe I should have specified ashift=12 when creating the pool, as the 3TB WD Green are 4K drives. :x

I run zpool iostat during a scrub and got the following…

Code: Select all
marks-mac-pro:~ mark$ zpool iostat 2
                capacity       operations       bandwidth
pool         alloc    free    read   write    read   write
----------  ------  ------  ------  ------  ------  ------
Ocean       5.42Ti  2.76Ti      32      24  1.33Mi   923Ki
Ocean       5.42Ti  2.76Ti     783     119  87.4Mi   893Ki
Ocean       5.42Ti  2.76Ti     420       0  49.2Mi       0
Ocean       5.42Ti  2.76Ti    1013       0   117Mi       0
Ocean       5.42Ti  2.76Ti     998      50   108Mi   216Ki
Ocean       5.42Ti  2.76Ti     818       0  83.4Mi       0
Ocean       5.42Ti  2.76Ti     721       0  70.7Mi       0
Ocean       5.42Ti  2.76Ti     575      50  66.5Mi   216Ki
Ocean       5.42Ti  2.76Ti     710       0  87.1Mi       0
Ocean       5.42Ti  2.76Ti     578       0  69.1Mi       0
Ocean       5.42Ti  2.76Ti  1.02Ki      46   123Mi   198Ki
Ocean       5.42Ti  2.76Ti     995       4   119Mi  18.0Ki
Ocean       5.42Ti  2.76Ti  1.04Ki       0   127Mi       0
Ocean       5.42Ti  2.76Ti     950       0   113Mi       0
Ocean       5.42Ti  2.76Ti     574      50  66.8Mi   216Ki
Ocean       5.42Ti  2.76Ti     962       0   108Mi       0
Ocean       5.42Ti  2.76Ti     721       0  85.7Mi       0
Ocean       5.42Ti  2.76Ti     294      50  33.8Mi   216Ki
Ocean       5.42Ti  2.76Ti     640       0  76.4Mi       0
Ocean       5.42Ti  2.76Ti     716       0  85.1Mi       0
Ocean       5.42Ti  2.76Ti     737      50  87.6Mi   216Ki
Ocean       5.42Ti  2.76Ti    1004       0   119Mi       0
Ocean       5.42Ti  2.76Ti  1.10Ki       0   134Mi       0
Ocean       5.42Ti  2.76Ti    1018      50   120Mi   216Ki
Ocean       5.42Ti  2.76Ti  1.15Ki       0   136Mi       0
Ocean       5.42Ti  2.76Ti    1020       0   114Mi       0
Ocean       5.42Ti  2.76Ti  1.03Ki       0   111Mi       0


I know that WD Greens are not the FASTEST drives in the world, but I feel I should be getting better speeds than this. I'd hate to rebuild my raid from scratch as I've already copied 3TB of files to it. I observe occasional lag from finder, such as a delay in showing folder contents, etc. Even in column view. I'm wondering if this is something to do with not specifying ashift=12 in the zpool creation. I dunno. Terminal lists the directory just fine, meanwhile Finder is still thinking about it. Maybe this is something else entirely. Either way, I still don't feel it's as fast as it could/should be.

Does anybody have any benchmarks with WD Green drives, comparing the ashift set and not set?
markpaterson Offline


 
Posts: 9
Joined: Fri Oct 05, 2012 1:48 pm

Re: is ashift=12 recommended for 3TB WD Green drives?

Post by markpaterson » Fri Oct 05, 2012 2:25 pm

Additional information…

Code: Select all
marks-mac-pro:~ mark$ zfs get all Ocean
NAME   PROPERTY              VALUE                  SOURCE
Ocean  type                  filesystem             -
Ocean  creation              Tue Sep 18  8:56 2012  -
Ocean  used                  3.63Ti                 -
Ocean  available             1.74Ti                 -
Ocean  referenced            52.2Mi                 -
Ocean  compressratio         1.02x                  -
Ocean  mounted               yes                    -
Ocean  quota                 none                   default
Ocean  reservation           none                   default
Ocean  recordsize            128Ki                  default
Ocean  mountpoint            /Volumes/Ocean         default
Ocean  checksum              on                     default
Ocean  compression           on                     local
Ocean  atime                 on                     default
Ocean  devices               on                     default
Ocean  exec                  on                     default
Ocean  setuid                on                     default
Ocean  readonly              off                    default
Ocean  snapdir               visible                local
Ocean  canmount              on                     default
Ocean  copies                1                      default
Ocean  version               5                      -
Ocean  utf8only              on                     -
Ocean  normalization         formD                  -
Ocean  casesensitivity       insensitive            -
Ocean  refquota              none                   default
Ocean  refreservation        none                   default
Ocean  primarycache          all                    default
Ocean  secondarycache        all                    default
Ocean  usedbysnapshots       0                      -
Ocean  usedbydataset         52.2Mi                 -
Ocean  usedbychildren        3.63Ti                 -
Ocean  usedbyrefreservation  0                      -
Ocean  logbias               latency                default
Ocean  sync                  standard               default


and

Code: Select all
marks-mac-pro:~ mark$ zpool get all Ocean
NAME   PROPERTY       VALUE      SOURCE
Ocean  size           8.19Ti     -
Ocean  capacity       66%        -
Ocean  altroot        -          default
Ocean  health         ONLINE     -
Ocean  guid           8554943120831032297  default
Ocean  version        28         default
Ocean  failmode       continue   default
Ocean  listsnapshots  off        default
Ocean  autoexpand     off        default
Ocean  free           2.74Ti     -
Ocean  allocated      5.44Ti     -
Ocean  readonly       off        -
Ocean  ashift         0          default
markpaterson Offline


 
Posts: 9
Joined: Fri Oct 05, 2012 1:48 pm

Re: is ashift=12 recommended for 3TB WD Green drives?

Post by si-ghan-bi » Fri Oct 05, 2012 3:46 pm

I used that option and I think it should be done. You wouldn't see great speedups in the transfer rate, but response times would be some ms faster.
si-ghan-bi Offline


 
Posts: 145
Joined: Sat Sep 15, 2012 5:55 am

Re: is ashift=12 recommended for 3TB WD Green drives?

Post by shuman » Fri Oct 05, 2012 7:42 pm

OK, I see this over and over again. I also see it in the FAQ, but I did not do it with my AFD. The reason I didn't is because I had already destroyed the pool, and recopied the data twice. I saw Don's response to a post regarding 4k drives. Based on it I did not worry about the ashift.

dbrady wrote:In all cases where a whole disk, like /dev/diskN, is passed into zpool create, ZFS will end up on a 4K aligned partition boundary. If you use an existing slice, like /dev/disk4s3", that slice is probably already 4K aligned but there's nothing ZFS can do to fix it if it's not.


So in my mind and based on the above quote, I would say the ashift is unnecessary.

Right, Don?
- Mac Mini (Late 2012), 10.8.5, 16GB memory, pool - 2 Mirrored 3TB USB 3.0 External Drives
shuman Offline

User avatar
 
Posts: 96
Joined: Mon Sep 17, 2012 8:15 am

Re: is ashift=12 recommended for 3TB WD Green drives?

Post by shuman » Fri Oct 05, 2012 7:44 pm

- Mac Mini (Late 2012), 10.8.5, 16GB memory, pool - 2 Mirrored 3TB USB 3.0 External Drives
shuman Offline

User avatar
 
Posts: 96
Joined: Mon Sep 17, 2012 8:15 am

Re: is ashift=12 recommended for 3TB WD Green drives?

Post by NakkiNyan » Fri Oct 05, 2012 8:49 pm

OK, but is there a way to check if it did it correctly? I think I did it right but I am not positive and want a way to be sure before I move everything, start over, move back, re-add disk and spend 18 hours moving files and 44 hours reslivering.

And if it is 1 disk, can I remove just the 1 and change the disk to AF?
NakkiNyan Offline


 
Posts: 47
Joined: Tue Oct 02, 2012 12:19 pm

Re: is ashift=12 recommended for 3TB WD Green drives?

Post by grahamperrin » Fri Oct 05, 2012 11:21 pm

NakkiNyan wrote:… is there a way to check … 


If the three disks in the opening post still have device numbers 1, 2 and 3 then for markpaterson:

Code: Select all
sudo zdb -l /dev/disk1 | grep ashift


Code: Select all
sudo zdb -l /dev/disk2 | grep ashift


Code: Select all
sudo zdb -l /dev/disk3 | grep ashift


Reference, in the knowledge base for ZEVO: Advanced Format Drives.

As I read that article alongside the earlier topic 4k drives and ashift=12? – in its entirety – I believe that for an Advanced Format drive, it is appropriate to set the ashift property.

----

Here, for a drive that was almost certainly setup with ZEVO Setup Assistant.app (a feature of past versions of Silver Edition):

Code: Select all
macbookpro08-centrim:~ gjp22$ zpool get ashift tall
NAME  PROPERTY  VALUE   SOURCE
tall  ashift    12      local
macbookpro08-centrim:~ gjp22$ zpool history tall | grep ashift
2012-05-04.21:48:10 zpool create -f -o ashift=12 -O compression=off -O copies=1 -O casesensitivity=insensitive -O snapdir=visible tall /dev/dsk/GPTE_78301A52-4AFF-4D96-8DE9-E76ABC14909C
macbookpro08-centrim:~ gjp22$


----

In Mark's case, already we see:

Code: Select all
Ocean  ashift         0          default
Last edited by grahamperrin on Fri Oct 05, 2012 11:33 pm, edited 1 time in total.
grahamperrin Offline

User avatar
 
Posts: 1596
Joined: Fri Sep 14, 2012 10:21 pm
Location: Brighton and Hove, United Kingdom

Re: is ashift=12 recommended for 3TB WD Green drives?

Post by NakkiNyan » Fri Oct 05, 2012 11:33 pm

I tried that before but when I hit enter and enter my password nothing shows up; it just takes me back to a prompt.

I am guessing it failed on all 4 HDD even though the pool says ashift 12. I just want the same speed from my raidz that I got from a single HDD using HFS+... I guess it is hopeless.

I do get this when looking at the pool...
Code: Select all
Suigintou:~ zak$ zpool get ashift Freya
NAME   PROPERTY  VALUE   SOURCE
Freya  ashift    12      local


the ZFS formatted slices come back 12 of course, just not the whole disk... Which is sorta the point.
NakkiNyan Offline


 
Posts: 47
Joined: Tue Oct 02, 2012 12:19 pm

Re: is ashift=12 recommended for 3TB WD Green drives?

Post by si-ghan-bi » Sat Oct 06, 2012 4:33 am

Before thinking the worst, why don't you try a real benchmark? The iostat command is not what you need to have reliable values: for example, it gives you average values and if you are not using the disk heavily, values are off.
si-ghan-bi Offline


 
Posts: 145
Joined: Sat Sep 15, 2012 5:55 am

Re: is ashift=12 recommended for 3TB WD Green drives?

Post by si-ghan-bi » Sat Oct 06, 2012 4:36 am

And more important: are there disadvantages in using the ashift command?
si-ghan-bi Offline


 
Posts: 145
Joined: Sat Sep 15, 2012 5:55 am

Next

Return to General Discussion

Who is online

Users browsing this forum: No registered users and 2 guests

cron