Bestbuy - 14tb easystore external hard drive - $200

josh

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Oct 21, 2013
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Drive is a WD140EMFZ, looks to be helium

r/DataHoarder already established it was a rebadged 530. Theory is they failed the tests at 7200rpm so they slowed it down and stuck it in low warranty period drives
 
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e97

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Jun 3, 2015
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This thread: Bestbuy WD Easystore 14TB shucked : DataHoarder ?

The drives I got from the 14TB EasyStore are all WD140EMFZ-11A0WA0

One of the drives shows double the write OPs as the other drives for an equivalent amount of data written.

Makes me think one of the drives has half the cache => drives have differences

All drives are in a raidz2:

Code:
                capacity     operations     bandwidth
pool           alloc   free   read  write   read  write
-------------  -----  -----  -----  -----  -----  -----
tank          15.9T  47.8T      0  4.14K      0   711M
  raidz2      15.9T  47.8T      0  4.14K      0   711M
    14-0          -      -      0    751      0   142M
    14-1          -      -      0    754      0   142M
    14-2          -      -      0    753      0   142M
    14-3          -      -      0    733      0   143M
    14-4          -      -      0  1.22K      0   143M
-------------  -----  -----  -----  -----  -----  -----
 
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josh

Active Member
Oct 21, 2013
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This thread: Bestbuy WD Easystore 14TB shucked : DataHoarder ?

The drives I got from the 14TB EasyStore are all WD140EMFZ-11A0WA0

One of the drives shows double the write OPs as the other drives for an equivalent amount of data written.

Makes me think one of the drives has half the cache => drives have differences

All drives are in a raidz2:

Code:
                capacity     operations     bandwidth
pool           alloc   free   read  write   read  write
-------------  -----  -----  -----  -----  -----  -----
tank          15.9T  47.8T      0  4.14K      0   711M
  raidz2      15.9T  47.8T      0  4.14K      0   711M
    14-0          -      -      0    751      0   142M
    14-1          -      -      0    754      0   142M
    14-2          -      -      0    753      0   142M
    14-3          -      -      0    733      0   143M
    14-4          -      -      0  1.22K      0   143M
-------------  -----  -----  -----  -----  -----  -----
Is that a forbidden 5-drive Z2?
 
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e97

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Jun 3, 2015
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Is that a forbidden 5-drive Z2?
Haven't heard of this.. there are posts from users about this but its debunked by ZFS developer Matthew Ahrens

The following ZFS pool configurations are optimal for modern 4K sector harddrives:
RAID-Z: 3, 5, 9, 17, 33 drives
RAID-Z2: 4, 6, 10, 18, 34 drives
RAID-Z3: 5, 7, 11, 19, 35 drives


The trick is simple: substract the number of parity drives and you get:
2, 4, 8, 16, 32 ...

This has to do with the recordsize of 128KiB that gets divided over the number of disks. Example for a 3-disk RAID-Z writing 128KiB to the pool:
disk1: 64KiB data (part1)
disk2: 64KiB data (part2)
disk3: 64KiB parity

Each disk now gets 64KiB which is an exact multiple of 4KiB. This means it is efficient and fast. Now compare this with a non-optimal configuration of 4 disks in RAID-Z:
disk1: 42,66KiB data (part1)
disk2: 42,66KiB data (part2)
disk3: 42,66KiB data (part3)
disk4: 42,66KiB parity

Now this is ugly! It will either be downpadded to 42.5KiB or padded toward 43.00KiB, which can vary per disk. Both of these are non optimal for 4KiB sector harddrives. This is because both 42.5K and 43K are not whole multiples of 4K. It needs to be a multiple of 4K to be optimal.
RAIDZ2 on 5 disks? - XigmaNAS
ZFS / RAIDz question


A misunderstanding of this overhead, has caused some people to recommend using "(2^n)+p" disks, where p is the number of parity "disks" (i.e. 2 for RAIDZ-2), and n is an integer. These people would claim that for example, a 9-wide (2^3+1) RAIDZ1 is better than 8-wide or 10-wide. This is not generally true.
How I Learned to Stop Worrying and Love RAIDZ | Delphix

data is system backups and media.

zpool properties:
compression=lz4
recordsize=128K

compression=lz4 has better performance than compression=off

The inequal parity blocks doesnt explain the higher write IO on the last drive. If it were the case, all drives in the pool would show higher write IO for the non full block write penalty.

ashift=12 helps with 4k alignment. Unsure how it affects the above.

5 x 14TB raid-z1 had the same issue with the last drive having higher write IO.

Got a 14TB hot spare, can benchmark 6 drive raid-z2 and see if the 14TBs are worth keeping.

Long story short: went back to my 8TB array because it has consistent performance.
 
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josh

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Oct 21, 2013
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Haven't heard of this.. there are posts from users about this but its debunked by ZFS developer Matthew Ahrens



RAIDZ2 on 5 disks? - XigmaNAS
ZFS / RAIDz question




How I Learned to Stop Worrying and Love RAIDZ | Delphix

data is system backups and media.

zpool properties:
compression=lz4
recordsize=128K

compression=lz4 has better performance than compression=off

The inequal parity blocks doesnt explain the higher write IO on the last drive. If it were the case, all drives in the pool would show higher write IO for the non full block write penalty.

ashift=12 helps with 4k alignment. Unsure how it affects the above.

5 x 14TB raid-z1 had the same issue with the last drive having higher write IO.

Got a 14TB hot spare, can benchmark 6 drive raid-z2 and see if the 14TBs are worth keeping.

Long story short: went back to my 8TB array because it has consistent performance.
Wouldn't mind if you tossed some 14TBs my way if you decide to ditch them. I'm regretting only buying 4. Trying to decide if I should sacrifice 8TB of space by doing a 6-drive Z2 with the 2x12TBs I have.
 
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