Topic
  • 5 replies
  • Latest Post - ‏2010-04-06T20:59:16Z by ord_mike
ord_mike
ord_mike
14 Posts

Pinned topic Advice on SAN configuration

‏2010-02-18T17:03:27Z |
I'm setting up a new VMWare environment, and am seeking advice on how to configure the SAN storage. This is my first time setting up VMs to run in a SAN, but I have set VMWare ESX/Server in the past so I'm pretty familiar with vmware. We are a small company, with about 100 users so none of our servers are working very hard to support the load. I was able to make the case for good equipment: 2 new IBM x3650M2 servers, with 26GB memory, dual E5520 procs, and QLogic iSCSI HBAs, connected to dual Cisco 3560G switches for redundancy. The SAN is an IBM DS3300 with dual controllers and (8) 450GB 15K SAS drives. We will be virtualizing quite a few servers over this year on vSphere 4 with ESXi 4.0 U1 installable. To start, we will be running 4 VMs. VMs are: 1 SQL 2005 server, and 1 IIS 6 server which serves pages to employees fed by the SQL server. Another server running vCenter and SQL 08. Last one is an XP box that does not generate a lot of proc/mem/disk use. Eventually, we will probably also convert our domain controllers, and development IIS/DB servers. So over the next 2 years, I can foresee, in total, 8-10 VMs running on these hosts.

Before I start conversions I wanted to get some input on my setup, specifically regarding if my storage config will be able to handle the load, or should I use a different setup. The OS images and databases will be stored in this SAN, and I'll probably set up a LUN to contain each OS and DB disk file. My initial plan is to set this up as all the drives in a RAID 6 array. My questions are:

Is it a bad idea to set up all the disks in one RAID6 array or should I divide it up more? For example use 2 disks in a RAID1 array for the OS images, and the rest in a RAID 6 array for all my databases?

Am I limited in the number of LUNs I can create? Looking at the ds3300 interface, seems that I can only create 31 LUNs.

Any other advice/observations/etc appreciated. Thanks!
Updated on 2010-04-06T20:59:16Z at 2010-04-06T20:59:16Z by ord_mike
  • pavel.alexei
    pavel.alexei
    335 Posts

    Re: Advice on SAN configuration

    ‏2010-02-22T16:13:47Z  
    Some your questions are examined the in next books
    "VMware Implementation with IBM Midrange System Storage"
    http://www.redbooks.ibm.com/redpieces/abstracts/redp4609.html?Open
    "VMware Proof of Practice and Performance Guidelines on the SAN Volume Controller"
    http://www.redbooks.ibm.com/abstracts/redp4601.html
    May be there you'll found some guides and answers.
    Unfortunately i don't have big experience.
    Regarding how to "divide" disks, 8 disks is a very small number to try to optimize.
    One remark: Raid-6 is better to build on 6 (4+2) or 10 (8+2) disks, RAID-5 on 5 (4+1) or 9 (8+1).
    IMHO will be better to create one RAID5 from 5 disks + 1 hotspare.
    IMHO Raid-6 is for big SATA drives, when rebuilding from failed disk can continue several days, in that time another disk can fail.
  • pavel.alexei
    pavel.alexei
    335 Posts

    Re: Advice on SAN configuration

    ‏2010-02-23T07:36:10Z  
    Some your questions are examined the in next books
    "VMware Implementation with IBM Midrange System Storage"
    http://www.redbooks.ibm.com/redpieces/abstracts/redp4609.html?Open
    "VMware Proof of Practice and Performance Guidelines on the SAN Volume Controller"
    http://www.redbooks.ibm.com/abstracts/redp4601.html
    May be there you'll found some guides and answers.
    Unfortunately i don't have big experience.
    Regarding how to "divide" disks, 8 disks is a very small number to try to optimize.
    One remark: Raid-6 is better to build on 6 (4+2) or 10 (8+2) disks, RAID-5 on 5 (4+1) or 9 (8+1).
    IMHO will be better to create one RAID5 from 5 disks + 1 hotspare.
    IMHO Raid-6 is for big SATA drives, when rebuilding from failed disk can continue several days, in that time another disk can fail.
    Sorry, i I was hurrying on when wrote message.
    > will be better to create one RAID5 from 5 disks + 1 hotspare.
    perhaps better could be one RAID-5 from 7 disks and 1 hotspare. Isn't the best option, but you can lose considerable more trying to acquire some indefinite performance improvements with such few disks.
    I looked through my library and found DS3300 implementation cookbook. Unfortunately i don't remember where i've got it.
    "Best Practices for Configuring the IBM System Storage DS3300 and an IP SAN"
    ftp://ftp.msys.md/IPSANBestPractices061109.pdf
  • lodevd
    lodevd
    5 Posts

    Re: Advice on SAN configuration

    ‏2010-02-24T16:45:14Z  
    Sorry, i I was hurrying on when wrote message.
    > will be better to create one RAID5 from 5 disks + 1 hotspare.
    perhaps better could be one RAID-5 from 7 disks and 1 hotspare. Isn't the best option, but you can lose considerable more trying to acquire some indefinite performance improvements with such few disks.
    I looked through my library and found DS3300 implementation cookbook. Unfortunately i don't remember where i've got it.
    "Best Practices for Configuring the IBM System Storage DS3300 and an IP SAN"
    ftp://ftp.msys.md/IPSANBestPractices061109.pdf
    In my experience I suggest the following:

    • I should start with 1 VMFS datastore of 100Gb on a RAID 5 for the OS of the 4 servers (for example 20GB / server OS)
    • If new VM's are added create a new datastore

    Creating multiple VMFS datastores gives more performance than creating 1 big VMFS datastore
    For the data of the SQL server I would use raw device maps on other arrays than the VMFS datastore:

    • 1 RDM disk for the sql server data files on a raid 5
    • 1 RDM disk for the sql server log files on a raid 1

    The vcenter server, IIS and XP can be on the VMFS datastore using virtual disks.

    I would not suggest RAID 6, because write performance is even less than on RAID 5
  • lodevd
    lodevd
    5 Posts

    Re: Advice on SAN configuration

    ‏2010-02-24T17:02:05Z  
    • lodevd
    • ‏2010-02-24T16:45:14Z
    In my experience I suggest the following:

    • I should start with 1 VMFS datastore of 100Gb on a RAID 5 for the OS of the 4 servers (for example 20GB / server OS)
    • If new VM's are added create a new datastore

    Creating multiple VMFS datastores gives more performance than creating 1 big VMFS datastore
    For the data of the SQL server I would use raw device maps on other arrays than the VMFS datastore:

    • 1 RDM disk for the sql server data files on a raid 5
    • 1 RDM disk for the sql server log files on a raid 1

    The vcenter server, IIS and XP can be on the VMFS datastore using virtual disks.

    I would not suggest RAID 6, because write performance is even less than on RAID 5
    ...one more thing.

    Just see that you only have 8 disks in your storage device.
    so you can not create 2x RAID 5 arrays and 1x RAID 1 (except without hot spare)

    So I would do the following:

    1x RAID 5 with 3 disks --> 1 LUN of 100GB for the VMFS datastore + 1 LUN for a RDM disk for the data files of the SQL server
    1x RAID 1 with 2 disks --> 1 LUN for a RDM disk for the log files of the SQL server
    1 hotspare

    You will have 2 disks left for growth.
  • ord_mike
    ord_mike
    14 Posts

    Re: Advice on SAN configuration

    ‏2010-04-06T20:59:16Z  
    thanks pavel and lodevd for your time and input on this. Using your advice I've changed my disk layout- raid 1 for OS/sql logs, and raid 5 for sql database files. I've been doing some disk benchmarking so I'll post results once the new setups are in place.