Calculate CPG maximum size

[nguyenhuukhoi]

Hello guys, pls help me!

Can you tell me how calculate CPG maximum size. I was looked for all for google sama, but I cannot found any answers.

[nsnidanko88]

For example you have 20TB of Free FC capacity, then using

 CPG with raid type 1 and set size 2 will give you 10TB of usable space (20TB * 0.5) - for each 1 GB of data you lose 1 GB for parity (in case of Raid 1 it's copy)

CPG with raid type 5 and set size 3 data 1 parity will give you 15TB of usable space (20TB * 0.75) - for each 3GB of data to lose 1 GB for parity

[nguyenhuukhoi]

 Thank you much, could you help me other questions?

- if I have 20TB disk usagem then I have create raid 10 and raid 5 on it. How can i know how much disk space use for raid 10 and raid 5?

if i use raid 5 and raid 6 on hp 3par storage system, and I lost 2 disks, then raid 5 lost data and raid 6 still remain?

[yapkl]

showspace -cpg will give you the info. Look at estfree->ldfree column.


"if i use raid 5 and raid 6 on hp 3par storage system, and I lost 2 disks, then raid 5 lost data and raid 6 still remain?"

Short answer - yes.
Long answer - it depends, if the two disks you lose does not contain the raidlets from the same "raid set" then you won't lose data. E.g. two disks belonging to two different nodes, or two disks in the same enclosure in a HA CAGE layout (you can lose the entire enclosure and not lose data in this case).

Anyway, you should be using R6 today on any 3PAR, unless you really have very high write performance requirements. If you have dynamic optimization, you can tune this online to any of the RAID 6 layouts depending on your requirements.

[c_montero]

Hello,

Sorry to activate a long sleeping post, but recently I got to manage a 3PAR storage and I'm still uneasy managing space usage and growth.

How can I know how much space I have available with this configuration?

28 drives, 1.6TB size with Raid 5 (3+1)

thanks in advance,

Christian M.

[Sheldon Smith]

The drives are broken into 1 GB chunkets. Using a CPG, volumes can be created either thin or fully provisioned. The command "showsys -space" will show how much free space you have available in (raw) chunkets - no RAID.

The command "showspace [-cpg <CPG_name>]" will show estimated free space for logical disk creation.

The system has default usage alerts as the free pool reaches 50% full, 75%, 85% and 95%. The command "showsys -param" will show if the Raw Space Alert for your device type(s) has been changed from the default.