Matt Connolly's Blog

my brain dumps here…

Western Digital Green Lemon

I have an OpenSolaris backup machine with 2 x 1.5 TB drives mirrored. One is a Samsung Silencer, the other is a Western Digital Green drive. The silencer is, ironically, the noisier of the two, but way outperforms the WD drive.

I’ve done some failure tests on the mirror by unplugging one drive while copying files to/from the backup server from my laptop.

First, I was copying from the server, onto a single FW drive, writing at a solid 30MB/s. I disconnected the Samsung drive while it was running and the file copy proceeded without fault at about 25MB/s of the single WD drive.

`zpool status` showed the drive was UNAVAIL and that the pool would continue to work in a degraded state. When I reconnected the drive, `cfgadm` showed it as connected by unconfigured. When I reconfigured the Samsung drive, the pool automatically resilvered any missing data. (wasn’t much because I was reading from the network) in a matter of seconds.

Failure test #2 was to remove the WD drive. I copied data to the server from the laptop, and the progress was intermittent… bursts of 30MB/s, then nothing for quite a few seconds, etc…. I disconnected the WD drive, and hey presto, the transfer rate instantly jumped up to a solid 20MB/s. This samsung drive definitely writes a whole stack faster than the WD drive. (A mirror is as fast as the slowest writing drive).

And here’s the lemon part. When I reconnected the WD drive, it showed up as disconnected. The samsung was connected, but unconfigured. To my frustration, I couldn’t reconnect the drive:

$ cfgadm
Ap_Id                          Type         Receptacle   Occupant     Condition
sata1/0                        sata-port    disconnected unconfigured failed
$ cfgadm -c connect sata1/0
cfgadm: Insufficient condition
I did a bit of searching and found this page: SolarisZfsReplaceDrive : use the -f force option:
$ pfexec cfgadm -f -c connect sata1/0
Activate the port: /devices/pci@0,0/pci8086,4f4d@1f,2:0
This operation will enable activity on the SATA port
Continue (yes/no)? yes
$ cfgadm
Ap_Id                          Type         Receptacle   Occupant     Condition
sata1/0                        disk         connected    unconfigured unknown
sata1/1::dsk/c8t1d0            disk         connected    configured   ok

So, now OpenSolaris sees the drive as connected, let’s configure it and zpool should see it straight away…

$ pfexec cfgadm -c configure sata1/0
$ cfgadm
Ap_Id                          Type         Receptacle   Occupant     Condition
sata1/0::dsk/c8t0d0            disk         connected    configured   ok
sata1/1::dsk/c8t1d0            disk         connected    configured   ok
$ zpool status -x
  pool: rpool
 state: ONLINE
status: One or more devices has experienced an unrecoverable error.  An
        attempt was made to correct the error.  Applications are unaffected.
action: Determine if the device needs to be replaced, and clear the errors
        using 'zpool clear' or replace the device with 'zpool replace'.
   see: http://www.sun.com/msg/ZFS-8000-9P
 scrub: resilver in progress for 0h0m, 0.00% done, 465h28m to go
config:

        NAME          STATE     READ WRITE CKSUM
        rpool         ONLINE       0     0     0
          mirror-0    ONLINE       0     0     0
            c8t0d0s0  ONLINE       0 1.14K     0  544K resilvered
            c8t1d0s0  ONLINE       0     0     0

Oh man… I have to resilver the whole drive. Why!!??! The other drive remembered it was a part of the pool and intelligently went about resilvering the differences. This drive looks like it was to resilver the whole damn thing.

After a while:

$ zpool status
  pool: rpool
 state: ONLINE
status: One or more devices is currently being resilvered.  The pool will
        continue to function, possibly in a degraded state.
action: Wait for the resilver to complete.
 scrub: resilver in progress for 0h23m, 5.05% done, 7h20m to go
config:

        NAME          STATE     READ WRITE CKSUM
        rpool         ONLINE       0     0     0
          mirror-0    ONLINE       0     0     0
            c8t0d0s0  ONLINE       0     0     0  12.3G resilvered
            c8t1d0s0  ONLINE       0     0     0

And here’s another interesting bit… the performance of the WD drive (c8t0d0) on my machine is really poor:

$ iostat -x 5

                    extended device statistics              
    r/s    w/s   kr/s   kw/s wait actv wsvc_t asvc_t  %w  %b device
    0.0   61.2    0.0 1056.2  0.0  9.1    0.0  148.1   0 100 c8t0d0
   79.0    0.0  978.7    0.0  0.0  0.0    0.0    0.6   0   3 c8t1d0
    0.0    0.0    0.0    0.0  0.0  0.0    0.0    0.0   0   0 c9t0d0
                    extended device statistics              
    r/s    w/s   kr/s   kw/s wait actv wsvc_t asvc_t  %w  %b device
    0.0   72.0    0.0  178.8  0.0  7.2    0.0   99.6   0 100 c8t0d0
  111.8    0.0  361.3    0.0  0.0  0.0    0.0    0.3   0   1 c8t1d0
    0.0    0.0    0.0    0.0  0.0  0.0    0.0    0.0   0   0 c9t0d0
                    extended device statistics              
    r/s    w/s   kr/s   kw/s wait actv wsvc_t asvc_t  %w  %b device
    0.0   51.6    0.0  120.4  0.0  7.5    0.0  145.9   0 100 c8t0d0
   79.4    0.0  143.7    0.0  0.0  0.0    0.0    0.2   0   1 c8t1d0
    0.0    0.0    0.0    0.0  0.0  0.0    0.0    0.0   0   0 c9t0d0
                    extended device statistics              
    r/s    w/s   kr/s   kw/s wait actv wsvc_t asvc_t  %w  %b device
    0.0   62.2    0.0 1968.5  0.0  8.3    0.0  133.7   0 100 c8t0d0
   81.8    0.0 2616.7    0.0  0.0  0.3    0.0    3.2   0   8 c8t1d0
    0.0    0.0    0.0    0.0  0.0  0.0    0.0    0.0   0   0 c9t0d0
                    extended device statistics              
    r/s    w/s   kr/s   kw/s wait actv wsvc_t asvc_t  %w  %b device
    0.0   34.6    0.0 1880.2  0.0  7.1    0.0  204.9   0  79 c8t0d0
   28.4   11.6 1413.5   41.7  0.0  0.1    0.0    3.1   0   7 c8t1d0
    0.0    0.0    0.0    0.0  0.0  0.0    0.0    0.0   0   0 c9t0d0

Check it out. 100% busy use of the drive, and it’s writing less than 2MB/s. Compare that to the %b busy for the Samsun (on c8t1d0) for reading the same amount of data. And check out the average service time (asvc_t) – that’s bad like a cd-rom!! Yikes.

It doesn’t get reconnect to the system, its service time is way slow and its write performance stinks. This WD drive is a total lemon!

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

%d bloggers like this: