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natewilson
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iSCSI for dummies (or at least for a Unix / NFS guy)?

I currently use NFS for my datastores in a small lab environment, with 6 ESX hosts and a couple Linux servers all mounting the same NFS share. Now I'm looking into deploying an iSCSI datastore, and I've been a bit confused by some of the questions and caveats I've seen in posts here.

Can anyone recommend a good resource for ramping up on iSCSI, specifically as related to its use with ESX and limitations to be aware of and architect for?

Such as:

- Attaching several ESX hosts and Linux servers to the same iSCSI export (LUN?)

- Best practices for organizing VMs to iSCSI shares.

- Implications of "LUNs". If I understand this correctly, a LUN is a logical SCSI disk. Are there limits to VMs per LUN or iSCSI clients attaching to LUNs?

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jbogardus
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Be aware that as far as VMware manuals, both of these cover iSCSI details:

Use of iSCSI functionality can often require that you understand this more than you might for other storage types:

My own tendencies:

Create LUNs of 500 GB - this is based on VMware recommendation of limiting LUNs to around 20 VMs

Store boot and small partitions in VMFS datastore. For larger partitions you may want to use iSCSI initiator to benefit more from some advanced SAN functionality. I find this is definately useful for Windows VMs on good iSCSI SANs, but don't know how much it applies to Linux VMs.

As for all datastores you may have VM snapshots on try to keep around 20% free space. Also account for the size of swap files on datastores - by default they will be created the same size as the VMs configured memory when the VM is powered on.

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DSTAVERT
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http://www.vmware.com/resources/techresources/1026

compare Protocols (iSCSI NFS)

http://www.vmware.com/resources/techresources/1006

iSCSI deployment

-- David -- VMware Communities Moderator
jbogardus
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Be aware that as far as VMware manuals, both of these cover iSCSI details:

Use of iSCSI functionality can often require that you understand this more than you might for other storage types:

My own tendencies:

Create LUNs of 500 GB - this is based on VMware recommendation of limiting LUNs to around 20 VMs

Store boot and small partitions in VMFS datastore. For larger partitions you may want to use iSCSI initiator to benefit more from some advanced SAN functionality. I find this is definately useful for Windows VMs on good iSCSI SANs, but don't know how much it applies to Linux VMs.

As for all datastores you may have VM snapshots on try to keep around 20% free space. Also account for the size of swap files on datastores - by default they will be created the same size as the VMs configured memory when the VM is powered on.

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Jackobli
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You got already useful hints.

I am just dropping in and want to know, what are your expectations on iSCSI?

Do you get iSCSI HBA or will you use standard network cards (Software iSCSI)?

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TimPhillips
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Depending on version of your ESX Server you can face troubles with hardware support.

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natewilson
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Thanks for the responses. The linked documents had a lot of good info. My main concerns were around the ability to attach to iSCSI shares from multiple ESX hosts.. Some things I read made it sounds like this was a problem but it sounds like this is do-able. I'll give it a try.

am just dropping in and want to know, what are your expectations on iSCSI?

Do you get iSCSI HBA or will you use standard network cards (Software iSCSI)?

I have had some poor performance with NFS FreeNAS shares and ESX. The performance is much below the performance I get when mounting the shares from Linux servers. I have seen reports of better iSCSI performance, so this is primarily an experiment to verify that and get some hands-on experience to compare the two protocols.

Since it's primarily an experiment, I have not installed new HBAs to offload the overhead of iSCSI. If it turns out successful, I will upgrade my hosts and migrate more/all shares to iSCSI.

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Jackobli
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I have had some poor performance with NFS FreeNAS shares and ESX.

Hum... well, FreeNAS... I really like the ease of install and the gui, but about performance one could start some discussions.

>I have seen reports of better iSCSI performance, so this is primarily an experiment to verify that and get some hands-on experience to compare the two protocols.

You should throw "comparison nfs iscsi vmware" onto the search engine of your choice.

If have read some postings about, but did not have had the change to test myself (all projects stuck at 90% due to lack of time / money Smiley Sad ).

If there is no hardware based acceleration, under heavier io, iSCSI may put more load on the CPU and therefore easier reach its limit.

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TimPhillips
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Hope it will hepl you. Anyway, I suggest you to use software iSCSI target - for now I don`t know any software iSCSI target supporting iSCSI offload, but software targets can offer you more advanced set of functions. For using I recommend you to use Starwind - for testing avaivble free version.

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