Re: ASM and VMWARE

Hi Lewis,

Oracle recommends using four (4) or more disks in each disk group. Having multiple disks in each disk group
spreads kernel contention accessing and queuing for the same disk.

https://docs.oracle.com/cd/E11882_01/server.112/e10803/config_storage.htm#HABPT4790

The number of LUNs (Oracle ASM disks) for each disk group should be at least equal to four times the number
of active I/O paths. For example, if a disk group has two active I/O paths, then minimum of eight LUNs
should be used. The LUNs should be of equal size and performance for each disk group.
An I/O path is a distinct channel or connection between storage presenting LUNs and the server. An active
I/O path is an I/O path in which the I/O load on a LUN is multiplexed through multipathing software.
Ensure that all Oracle ASM disks in a disk group have similar storage performance and availability
characteristics. In storage configurations with mixed speed drives, such as flash memory and hard disk drives
(HDD), I/O performance is constrained by the slowest speed drive.

https://docs.oracle.com/en/database/oracle/oracle-database/19/ostmg/considerations-asm-storage.html#GUID-18D7AFB2-F417-4E1F-B3B0-02585E385818

Multiple ASM disks allow for multiple I/O queues in the OS, and so can assist with performance. However
too many disks may prove cumbersome to manage.

Regards,
Osman DİNÇ
https://dincosman.com

Ed Lewis <eglewis71_at_gmail.com>, 14 Haz 2024 Cum, 21:57 tarihinde şunu yazdı:

> Hi,
>
> I recently took on a project with a new client.
>
> I’m tasked with building several databases in a RAC environment (19.23)
>
>
>
> ASM is being used with VMWARE on a EMC Unity Array. I recommended
>
> creating a few disk groups with a minimum of 4 LUNS (same size) for each
> group.
>
>
>
> The unix admin is against doing that saying that just use 1 large
> disk for each group.
>
> He says it’s a disadvantage when using a virtual disk infrastructure
> like we have with our EMC Unity disk farm.
>
> He states it is actually a disadvantage to carve up such small
> physical disks at the SAN Storage Array processor
>
> level and is not actually even possible as only whole disks can be
> assigned to a particular use at that level.
>
>
>
> Although, I have not worked much with VMWARE, I’ve never heard of
> these restrictions
>
> when using ASM, so I have my doubts.
>
> Any thoughts or experiences on this would be greatly appreciated
> --
> http://www.freelists.org/webpage/oracle-l
>
>
>

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