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vSphere RDM used\compressed space representation on Nimble

Question asked by Dmitry Grab on Jan 11, 2017
Latest reply on Jan 13, 2017 by Dmitry Grab

Could somebody please explain the meaning of the Compression and the Space Saved in the examples below?

 

In Example #1 the Used space on the SAN end is much larger than the actual used space in Windows (1.08 TB > 830 GB). Plus, there is mysterious Saved 527.41 GB due to compression.

 

Example #2 is less extreme (the Used space is more or less adequately displayed on both ends), but once again, there is also "Savings" of 2.35 TB.

 

Windows Disk properties reflect the real usage picture on both. Both RDMs are identically configured: Basic NTFS Volume, no Windows compression, Physical RDM, iSCSI, vSphere v5.5. Nimble CS460G-X2, 2.3.18.0-394708-opt

 

Thank you

 

RDM space usage Example #1


Windows Disk Properties

---

Capacity 1.1 TB

Used Space 830 GB

Free Space 295 GB

 

Nimble CS460G-X2

---

VOLUME SPACE  

Size 1.1 TB

Used 1.08 TB

Reserve 0 B

Quota 1.1 TB

Primary Compression 1.48X

Primary Space Saved 527.41 GB

 

SNAPSHOT SPACE  

Used 0 B

Reserve 0 B

Quota Unlimited

Backup Compression N/A

Number of Snapshots 0

 

 

RDM space usage Example #2

 

Windows Disk Properties

---

Capacity 8.99 TB

Used Space 6.71 GB

Free Space 2.28 GB

 

Nimble CS460G-X2

---

VOLUME SPACE  

Size 9.0 TB

Used 6.79 TB

Reserve 0 B

Quota 9.0 TB

Primary Compression 1.35X

Primary Space Saved 2.35 TB

 

SNAPSHOT SPACE  

Used 105.57 MB

Reserve 0 B

Quota Unlimited

Backup Compression 1.34X

Number of Snapshots 0

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