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Is this Bad I/O for this setup?
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Is this Bad I/O for this setup?

lele0108lele0108 Member
edited March 2012 in General

I have two WD Caviar Greens in RAID0, and I get around 50MB/s.

The Drives: http://www.newegg.com/Product/Product.aspx?Item=N82E16822136939 (They say they have 100MB/s sustained)

I set them up as RAID0.

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Comments

  • jhjh Member
    edited March 2012

    That does seem a little low. Are the disks new? Are you using a RAID card or MDADM?

    Thanked by 1lele0108
  • @jtodd said: That does seem a little low

    Grr. My host basically told me there is NOTHING they can do.

  • jhjh Member

    @lele0108 said: Grr. My host basically told me there is NOTHING they can do.

    BurstNET by any chance? I know they use green drives.

    Are you using a RAID card or MDADM?

  • Single WD Caviar Green drive writes at 40 MB/s and reads at 60 MB/s, so you should see much more than 50 MB/s in RAID 0.

  • @jtodd said: BurstNET by any chance? I know they use green drives.

    Are you using a RAID card or MDADM?

    I'm not 100% sure, but I think it's Software RAID (Anybody know how to tell?).

    No, I'm going with CheetahHost, who have their servers colo'd by CorporateColocation.

  • @iKocka said: Single WD Caviar Green drive writes at 40 MB/s and reads at 60 MB/s, so you should see much more than 50 MB/s in RAID 0.

    These drives say they have 100MB/s transfer, and people seem to get that speed too. Keep in mind these seem to be a new model.

  • jhjh Member
    edited March 2012

    @lele0108 said: I'm not 100% sure, but I think it's Software RAID (Anybody know how to tell?).

    cat /proc/mdstat
  • @jtodd said: cat /proc/mdstat

    [root@191 ~]# cat /proc/mdstat
    Personalities : [raid0] [raid1]
    md0 : active raid1 sda1[0] sdb1[1]
    511988 blocks super 1.0 [2/2] [UU]

    md1 : active raid0 sda2[0] sdb2[1]
    1952495616 blocks super 1.1 512k chunks

    unused devices:

  • jhjh Member

    Ok so you have a software RAID1 and a software RAID0 partition.

    Chances are you're getting that speed on the RAID1 partition which would make some sense.

    If you want to test the RAID0 partition try:

    hdparm -t /dev/md1
  • KairusKairus Member
    edited March 2012

    For RAID 0, software RAID will perform just as good as hardware. I don't think that's the issue here.

    edit: Just noticed the RAID 1 partition, why would they set it up like that?

  • lele0108lele0108 Member
    edited March 2012

    @jtodd said: Ok so you have a software RAID1 and a software RAID0 partition.

    Ok, I'm confused. Are you saying I have RAID0 AND RAID1?

    [root@191 ~]# hdparm -t /dev/md1

    /dev/md1:

    Timing buffered disk reads: 28 MB in 3.05 seconds = 9.19 MB/sec
    [root@191 ~]# hdparm -t /dev/md1

    /dev/md1:

    Timing buffered disk reads: 324 MB in 3.01 seconds = 107.81 MB/sec
    [root@191 ~]# hdparm -t /dev/md1

    /dev/md1:

    Timing buffered disk reads: 300 MB in 3.01 seconds = 99.58 MB/sec

  • jhjh Member

    @Kairus said: For RAID 0, software RAID will perform just as good as hardware. I don't think that's the issue here.

    I was actually thinking a dodgy RAID card.

  • jhjh Member
    edited March 2012

    @lele0108 said: Ok, I'm confused. Are you saying I have RAID0 AND RAID1?

    On different partitions, yes. You can use

    cat /etc/fstab

    to show where they're mounted.

    @lele0108 said: /dev/md1:

    Timing buffered disk reads: 28 MB in 3.05 seconds = 9.19 MB/sec

    Well that's worrying. Presumably this is a new server with nothing else running?

  • lele0108lele0108 Member
    edited March 2012

    @jtodd said: cat /etc/fstab

    Created by anaconda on Thu Mar 15 06:36:37 2012

    Accessible filesystems, by reference, are maintained under '/dev/disk'
    See man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info

    /dev/mapper/vg_191-LogVol00 / ext4 defaults 1 1
    UUID=ac3e0760-8311-4942-acdd-40f70eb8b71a /boot ext4 defaults 1 2
    /dev/mapper/vg_191-LogVol02 /vz ext4 defaults 1 2
    /dev/mapper/vg_191-LogVol01 swap swap defaults 0 0
    tmpfs /dev/shm tmpfs defaults 0 0
    devpts /dev/pts devpts gid=5,mode=620 0 0
    sysfs /sys sysfs defaults 0 0
    proc /proc proc defaults 0 0
    You have new mail in /var/spool/mail/root

    @jtodd said: Well that's worrying. Is there anything else on the server using lots of IO?

    The only thing on the server is SolusVM, and two virtual machines, that aren't really even active. (One has Kloxo installed, no sites being served, and the other one is blank)

  • jhjh Member
    edited March 2012

    Oh you've got LVMs on an OpenVZ system for some unknown reason:

    pvdisplay

    Also try the hdparm test for each disk. One might be dodgy:

    hdparm -t /dev/sda1 && hdparm -t /dev/sda2
  • @jtodd said: pvdisplay

    PV Name /dev/md1
    VG Name vg_191
    PV Size 1.82 TiB / not usable 2.00 MiB
    Allocatable yes
    PE Size 4.00 MiB
    Total PE 476683
    Free PE 1
    Allocated PE 476682
    PV UUID DzLmxJ-2K0l-7FNv-o58B-hMMp-wz5R-L47X40

    @jtodd said: hdparm -t /dev/sda1 && hdparm -t /dev/sda2

    /dev/sda1:
    Timing buffered disk reads: 158 MB in 3.01 seconds = 52.43 MB/sec

    /dev/sda2:
    Timing buffered disk reads: 22 MB in 3.59 seconds = 6.12 MB/sec

    My partitions are setup as:

    / = 1.92Gb
    /Boot = 484mb
    /vz = 1.78 Tb

  • jhjh Member

    Ok so it looks like you have one dodgy disk slowing down the system, /dev/sda2.

  • @jtodd said: Ok so it looks like you have one dodgy disk slowing down the system, /dev/sda2.

    What can I do to fix this?

    To make things worse, I did a IO test on one of the VPSs under SolusVM, and the I/O is horrible:

    536870912 bytes (537 MB) copied, 35.8906 seconds, 15.0 MB/s

  • Contact your host and show them the hdparm results, tell them the disk is dieing.

  • jhjh Member

    @Kairus said: Contact your host and show them the hdparm results, tell them the disk is dieing.

    What he said

    Thanked by 1lele0108
  • @jtodd said: What he said

    Ok, I'll talk to the host it. My I/O on my whole server pretty much dropped to 10MB/s.

  • jhjh Member

    @lele0108 said: Ok, I'll talk to the host it. My I/O on my whole server pretty much dropped to 10MB/s.

    Yeah, now would be a good time to ask for a RAID1 setup across the whole server as well, as RAID0 for hosting VPSs is anything but advisable.

  • JacobJacob Member

    green drives suck, I just traded my greens in. the WD10Ears drives I had only was doing 5400 RPM but westerndigital does not display this onsite.

    I recommend Samsung HD103UJ I have 2 drives in raid 1 with a 96MB/s speed consistantly.

  • @jtodd said: Yeah, now would be a good time to ask for a RAID1 setup across the whole server as well, as RAID0 for hosting VPSs is anything but advisable.

    All right, I've already sent it a ticket to look at the faulty drives. Thanks for all the help!

  • Single WD green drive (250gb)

     dd if=/dev/zero of=test bs=16k count=64k conv=fdatasync;rm test
    65536+0 records in
    65536+0 records out
    1073741824 bytes (1.1 GB) copied, 12.5311 s, 85.7 MB/s
  • @lele0108 said: Ok, I'm confused. Are you saying I have RAID0 AND RAID1?

    @jtodd said: On different partitions, yes. You can use

    at least for /boot/ partition you "must" use raid1

  • The green drives are going to be inconsistent in their performance because they have variable RPM.
    If this is also a racked server it could be due to vibration. Greens are not vibration proof like the REs or Blacks. We have seen their speed drop to 2-3 MB/s when used in a rack with many servers.

  • fanfan Veteran

    WD has a specific tool to disable the auto spin down, called WDidle3.

  • KuJoeKuJoe Member, Host Rep
    edited March 2012

    @lele0108 said: I have two WD Caviar Greens

    Sounds about right. They are nice if you are conscious about your power bill (and I hear they can be pretty quiet), but performance is not their strong point at all. I think the primary use for them is in a home desktop/server application.

    Thanked by 1Boltersdriveer
  • @KuJoe said: think the primary use for them is in a home desktop/server application.

    I think only the Black and Raid Edition are meant for enterprise usage, they might claim the Raptor is as well, but I think it's only purpose is RMA trading.

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