topic Re: what % of volume space VA7110 can be used in Disk Enclosures

what % of volume space VA7110 can be used

Md. Khairul Alam Prodha_4 — Mon, 21 Nov 2005 06:19:07 GMT

Hi,

We have one VA7110 with 15x73GB FC Hard Disk, Auto RAID, Total Physical size 1001.35GB and allocated 696GB on one Group and 66GB used for Active Hot Spare and unallocated 34GB and 204GB for Redundancy.

We are using total 585GB for 5 volumes of Oracle Database. Most of volumes showing uses above 90% at bdf output.

Could any one help me what % of volume we can use for best performance?
Is it below 70% of each volume or more?

Thanks

Re: what % of volume space VA7110 can be used

Luk Vandenbussche — Mon, 21 Nov 2005 06:22:35 GMT

Hi,

You have the best performance is you don't use more then 50 % of the capacity then al the data is store is raid-1, the more capacity you use the more data is stored in Raid5.

Re: what % of volume space VA7110 can be used

Md. Khairul Alam Prodha_4 — Mon, 21 Nov 2005 21:50:27 GMT

Hi,

We have Auto RAID. We have 5 logical volume each of them 117GB total 585GB. My question is what % of each logical volume 117GB we can use for best performance of array and Oracle Database. Now it is above 90%.
/dev/vgunicorn/lvol2
122683392 114910102 7287510 94% /u04
/dev/vgunicorn/lvol1
122683392 111464087 10518157 91% /u03
/dev/vgunicorn/lvol3
122683392 116347448 5940259 95% /u05
/dev/vgunicorn/lvol4
122683392 104556473 16998747 86% /u06
/dev/vgunicorn/lvol5
122683392 114559970 7615766 94% /u07

Thanks

Re: what % of volume space VA7110 can be used

Tobias Hartlieb — Tue, 22 Nov 2005 01:37:04 GMT

Hi,

be carefully, don't mix up two seperate things!

The "bdf" output gives the percentage of used space within the filesystem, i.e. how much data is used within the space reserved by the filesystem. But this has nothing to do with VA performance...

The performance of the VA is only dependent on the allocated space within the VA, i.e. the sum of the LUN sizes - compared to the unallocated space, which is for creating further LUNs. It is approx. the size, if all filesystems would be filled up with 100% data (bdf=100%). It's because the VA cannot tell if the data reserverd for a LUN is "good/valid" data or "free" data. It just reserves space for the allocated LUN and can not use it for performance improvements.

Therefore, you don't have to care at all for the bdf output, just for the ratio of allocated to unallocated space by your LUNs of the VA. This can all be obtained by the "armdsp -a" output... Here, a ratio of 70% as allocated space of total available space should be fine. Beyond 90% it could go really bad...

However, there is another thing like "magic capacity", which is always roughly at 50%. There might be severe performance Problems, if your allocated space (sum of LUN size on VA) is below (!) this threshold when you work in AutoRaid mode...

Regards.

Tobias