topic Best practice vmware iscsi lun dedupe in VMware Solutions Discussions

Best practice vmware iscsi lun dedupe

ramkump12345 — Thu, 05 Jun 2025 06:32:13 GMT

Hi All

Please can someone tell and explain to me the best practice when setting up vmware luns I want to maximize space savings, will the below make the lun go offline Im getting confused with fractional reserve, If i dedupe the volume will i get space savings back and from where, I want to protect the lun from going offline am hoping the autodelete and autogrow will stop it as we can monitor it in dfm.

volume guarantee none

set fractional reserve to 0%

snap reserve 20%

lun space guarantee off (thin)

autogrow volume 1gb at a time

snap autodelete maintain 20% free space

Thanks

Re: Best practice vmware iscsi lun dedupe

crocker — Tue, 20 Mar 2012 18:55:31 GMT

, this does not sound like a support issue. Is this something you team handles?
Mike

Re: Best practice vmware iscsi lun dedupe

lukasz_serda — Tue, 20 Mar 2012 19:40:14 GMT

Best practices is on lun wizard in VSC when you provision datastor or on SystemManager 2.0 when you ceate LUN.

My best practices.

Turn off snap reserve on volume (snap reserve 0) when you use snapshots on LUN System dont use that space. For snapshots on the lun system use volume free space.

Example vlume have 100gb Lun have 70gb space for snapshots is 30 gb on volume.

Fractional reserve example

Fractional reserve 100%

Lun have 20 WAFL BLOKS

VOLUME have 40 WAFL BLOCKs

When you create snapshot on datastore on 10 WAFL blocks system reserve 10 bloks in free space on volume

When you create secound snapshot on 10 (from the first snapshot) and 4 new block snapshot fractional reserve allocate 4 blocks on free volume space

Fractional reserve 20% CLI option

Lun have 20 WAFL BLOKS

VOLUME have 40 WAFL BLOCKs

When you create snapshot on datastore on 10 WAFL blocks system reserve 2 bloks in free space on volume

When you create secound snapshot on 10 (from the first snapshot) and 4 new block snapshot fractional reserve allocate 2 blocks on free volume space

If you use deduplication or snapshot you must check:

1. Alghin on datastore mbralghin tool

2. Tur on thin provisioning on lun on volume it is optional but in this case turn on it.

3. Check snapshots delete all unused unneeded snapshots.

For snapshot on Vmware use VSC.

I dont understand why youre volume grow so dramaticli, how many space you have ? Why you do not use tryfirst option or autogrow option?