IOPS calculation for SAN Design - Storage

This is a discussion on IOPS calculation for SAN Design - Storage ; Hi, we want to establish a SAN in near future and therefore we calculate the technical basics at the moment. First of all we are interested in disk performance, particularly with regard to iops and throughput. The capacity planer from ...

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  1. IOPS calculation for SAN Design

    Hi, we want to establish a SAN in near future and therefore we
    calculate the technical basics at the moment. First of all we are
    interested in disk performance, particularly with regard to iops and
    throughput. The capacity planer from VMware delivers the average
    values of PhysicalDisk\trans, PhysicalDisk\Bytes/s per server and
    overall. According to these results, we have only a few iops (peak
    load 162) with 20 servers. In this analysis I have no declaration of
    the peak value per server, so I tried to find it out with the
    Microsoft perfmon. Here I get some strange values. I logged the disk
    performance with perfmon during one day. Perfmon shows a peak value of
    PhysicalDisk\trans/s of over 2000 (iops) at a server witch two SATA
    disks (Raid-1). The technical datasheet of these disks contain a
    typical value of 85 iops. Can this be true? How can I get realistic
    peak values of really existing iops to make a realistic design?

    Thanks for help,

    Holger


  2. Re: IOPS calculation for SAN Design

    DataMover for Linux and Windows will provide this data for you. The
    application performs an automated performance test across 14 different
    tranfer sizes and records throughput and IOPS for each transfer size along
    with standard deviation values for each of these data points.

    Contact the Moojit for a 30 day evaluation license.

    www.moojit.net


    wrote in message
    news:1191675785.873476.283950@57g2000hsv.googlegro ups.com...
    > Hi, we want to establish a SAN in near future and therefore we
    > calculate the technical basics at the moment. First of all we are
    > interested in disk performance, particularly with regard to iops and
    > throughput. The capacity planer from VMware delivers the average
    > values of PhysicalDisk\trans, PhysicalDisk\Bytes/s per server and
    > overall. According to these results, we have only a few iops (peak
    > load 162) with 20 servers. In this analysis I have no declaration of
    > the peak value per server, so I tried to find it out with the
    > Microsoft perfmon. Here I get some strange values. I logged the disk
    > performance with perfmon during one day. Perfmon shows a peak value of
    > PhysicalDisk\trans/s of over 2000 (iops) at a server witch two SATA
    > disks (Raid-1). The technical datasheet of these disks contain a
    > typical value of 85 iops. Can this be true? How can I get realistic
    > peak values of really existing iops to make a realistic design?
    >
    > Thanks for help,
    >
    > Holger
    >




  3. Re: IOPS calculation for SAN Design

    On Sat, 06 Oct 2007 06:03:05 -0700, hw@hwi-networksecurity.de wrote:

    >Hi, we want to establish a SAN in near future and therefore we
    >calculate the technical basics at the moment. First of all we are
    >interested in disk performance, particularly with regard to iops and
    >throughput. The capacity planer from VMware delivers the average
    >values of PhysicalDisk\trans, PhysicalDisk\Bytes/s per server and
    >overall. According to these results, we have only a few iops (peak
    >load 162) with 20 servers. In this analysis I have no declaration of
    >the peak value per server, so I tried to find it out with the
    >Microsoft perfmon. Here I get some strange values. I logged the disk
    >performance with perfmon during one day. Perfmon shows a peak value of
    >PhysicalDisk\trans/s of over 2000 (iops) at a server witch two SATA
    >disks (Raid-1). The technical datasheet of these disks contain a
    >typical value of 85 iops. Can this be true? How can I get realistic
    >peak values of really existing iops to make a realistic design?
    >
    >Thanks for help,
    >
    >Holger


    Your stats are showing cache ops, not disk. If you use hardware raid
    the controller will have some amount of cache or even if you are using
    a single drive the OS will do write caching to memory unless you
    specifically mount the file system with forcedirectio (unix only, not
    sure what Windows uses).

    The thing about cache is that, no matter how much you have, you can
    only delay the inevitable if you have alot of IO. For instance, if
    you bottleneck on IO with 10G of cache after 30 seconds, adding
    another 10G of cache will only delay the bottleneck for 1 minute or
    so. If you are IOP intensive then you need to look at disk IOPS and
    cache will just be gravy.

    Disk IOPS are generally 80 for SATA and 120 for FC. Use those numbers
    to determine your requirements and you won't get bottlenecked.

    Something to keep in mind too, IOPS and throughput are not directly
    related. If you have 10 SATA drives you can get ~800 IOPS total, but
    if your data is large sequential you could get 200MB/sec of
    throughput.

    ~F

  4. Re: IOPS calculation for SAN Design

    On 6 oct, 08:03, h...@hwi-networksecurity.de wrote:
    > Hi, we want to establish a SAN in near future and therefore we
    > calculate the technical basics at the moment. First of all we are
    > interested in disk performance, particularly with regard to iops and
    > throughput. The capacity planer from VMware delivers the average
    > values of PhysicalDisk\trans, PhysicalDisk\Bytes/s per server and
    > overall. According to these results, we have only a few iops (peak
    > load 162) with 20 servers. In this analysis I have no declaration of
    > the peak value per server, so I tried to find it out with the
    > Microsoft perfmon. Here I get some strange values. I logged the disk
    > performance with perfmon during one day. Perfmon shows a peak value of
    > PhysicalDisk\trans/s of over 2000 (iops) at a server witch two SATA
    > disks (Raid-1). The technical datasheet of these disks contain a
    > typical value of 85 iops. Can this be true? How can I get realistic
    > peak values of really existing iops to make a realistic design?
    >
    > Thanks for help,
    >
    > Holger



    Hi Holger,

    First, and it's a rule, create your sizing at 70% of you peak, that's
    mean, if you have 2000 IOPS in your peak IO you must to configure your
    storage thinking in 2860 IOPS because it's a rule of the thumb, so,
    how many disks you need, depends, First you must consider, a physical
    disk can operate in average between 130 and 150 IOPS per disk, so, if
    you have 2860 IOPS you must to install 22 HDD aprox. and then you can
    obtain this 2860 IOPS. and depends of RAID level that you're using is
    the USABLE space that you can obtain, so here's another variable, cost
    per transaction. becuase if you are using RAID 5 you obtain more
    USABLE space than RAID 1+0.

    I hope that's information is useful for your.

    regards.


  5. Re: IOPS calculation for SAN Design


    Don't under estimate the value of cache. I believe if you have an
    intelligent raid controller using cache effectively you're backend
    disks won't need to meet the peak iops you measured in many
    situations.

    For example, are the 2000 iops a mixture of reads and writes. Read
    cache hits would require no physical disk operation. I have seen a
    hitachi 9980 serving storage for a multi terabyte transaction
    processing database maintain a very good cache hit rate.

    Also, when a raid controller has write cache it can stage writes to
    physical media efficiently so that 2000 iops from the host's view
    would result in something potentially much smaller on the array's
    backend disks.

    Regards,
    Vic


    On Oct 18, 9:58 pm, alexup wrote:
    > On 6 oct, 08:03, h...@hwi-networksecurity.de wrote:
    >
    >
    >
    > > Hi, we want to establish a SAN in near future and therefore we
    > > calculate the technical basics at the moment. First of all we are
    > > interested in disk performance, particularly with regard to iops and
    > > throughput. The capacity planer from VMware delivers the average
    > > values of PhysicalDisk\trans, PhysicalDisk\Bytes/s per server and
    > > overall. According to these results, we have only a few iops (peak
    > > load 162) with 20 servers. In this analysis I have no declaration of
    > > the peak value per server, so I tried to find it out with the
    > > Microsoft perfmon. Here I get some strange values. I logged the disk
    > > performance with perfmon during one day. Perfmon shows a peak value of
    > > PhysicalDisk\trans/s of over 2000 (iops) at a server witch two SATA
    > > disks (Raid-1). The technical datasheet of these disks contain a
    > > typical value of 85 iops. Can this be true? How can I get realistic
    > > peak values of really existing iops to make a realistic design?

    >
    > > Thanks for help,

    >
    > > Holger

    >
    > Hi Holger,
    >
    > First, and it's a rule, create your sizing at 70% of you peak, that's
    > mean, if you have 2000 IOPS in your peak IO you must to configure your
    > storage thinking in 2860 IOPS because it's a rule of the thumb, so,
    > how many disks you need, depends, First you must consider, a physical
    > disk can operate in average between 130 and 150 IOPS per disk, so, if
    > you have 2860 IOPS you must to install 22 HDD aprox. and then you can
    > obtain this 2860 IOPS. and depends of RAID level that you're using is
    > the USABLE space that you can obtain, so here's another variable, cost
    > per transaction. becuase if you are using RAID 5 you obtain more
    > USABLE space than RAID 1+0.
    >
    > I hope that's information is useful for your.
    >
    > regards.





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