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Swap space for HANA?

Former Member
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Dear all HANA expert,

I have a small HANA virtual machine running on Windows 7 hosts. There are 32 GB RAM in HANA guest. I am wondering whether I can utilize the Linux swap space to increase the memory capacity that can be allocated to HANA.

The reason why I want to do so is to install another VM running NetWeaver AS ABAP but I could not get more memory for HANA instance. Currently, the installation of NetWeaver AS ABAP keep on failing due to the error message of "Allocation Failed".

It would be appreciated if some one could help me tackle this bottleneck.

Thanks in advance.

Best Regards,

Accepted Solutions (0)

Answers (2)

Answers (2)

Former Member
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Dear All,

Thanks for all above discussions. It gave me some hints about solution alternatives. I just figured out one way to solve my situation.

Since I cannot have HANA to utilize the Linux internal swap space and physical memory is limited, I tried to set up a huge virtual memory on my Windows host. Then, I enlarge the memory size of the HANA virtual machine to 64G and initiate the AS ABAP installation. This solution works and SICK check with no error.

In other words, I used the virtual memory(pagefiles) on the host instead of using Linux swap space on the guest virtual machine. Not the best solution, however it's a workaround though.

Thanks for all the helps.

Best Regards,

Former Member
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Hi Edward,

Which VM did you use for HANA? According to my understanding, Hyper-V doesn't have a hypervisor swapping ability. So it is actually impossible to make VM memory size larger than physical memory in Hyper-V, it just won't start.

Or if you've used Hyper-V, would you please describe your VM settings and steps during VM startup?

Best regards.

lbreddemann
Active Contributor
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SAP HANA is absolutely not designed to run off swap memory.

You may see if you are able to get it running with less memory (use the allocation limit setting, maybe) and see how you go. But swapping is not meant to happen for SAP HANA systems.

Former Member
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Hi Lars,

Is ther a concept of Swaping in HANA ?

I belive no. what do you say ?

Regards,

Pavan Gunda

lbreddemann
Active Contributor
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Sorry mate, but as it is your question doesn't make sense to me.

What are you referring to?

OS level swapping?

Indexserver memory paging to disk?

Keep in mind that having all data to be worked on in memory is sort of key to an in-memory database...

Former Member
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OS level swaping.

lbreddemann
Active Contributor
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How would OS level swapping be a concept of SAP HANA?

Look, all coding inside of SAP HANA expects that the whole process memory is actually in RAM.

Does the system crash and throw error messages if you force it into paging? Probably not.

Does it work in any reasonable way? Probably not as well.

I already hinted you towards limiting the total amount of memory SAP HANA would want to allocate. If you want to use it in a tiny-weeny setup that might work for you.

Syamkriz
Active Participant
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Hi Pavan,

Swapping/Paging is an activity where RAM writes to Disk when it exceeds memory capacity. So if HANA dont use disk for processing how is SO swapping relevant for HANA?

Thanks and Regards,

Syam

Former Member
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Hi Sam,

Yes, you are correct. This is also my understanding is.

I have two question here

1 . HANA is nothing but complete RAM memory rite ? . So in case if the All memory is used up then the HANA system goes down rite ?

2. Lets say if i restart OS . the whole data in RAM will vanish rite?  Now, after OS restart..HANA

needs to load all the data from disk rite? or

what happens when i restart the OS ?

Regards,

Pavan Gunda

lbreddemann
Active Contributor
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Geeze... these questions tell me that you need to read up on some of the core concepts of SAP HANA.

I recommend you make yourself familiar with the usual SAP HANA primer documents.

That'll answer these questions.

Syamkriz
Active Participant
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Hi Pavan,

1. Dont know exactly , but it should throw errors. What you used to get when the disk is full in SAP NW systems? something similar to that should happen.

2.HANA has got a persistent storage to handle restarts. It inflates HANA memory.

I think you ask this questions either to test my knowledge or just out of laziness to read documents...no offence meant...but i see you advise others on HANA topics and i have decided to follow you a few hours back..so just confused...how come you work on the db without knowing all this?

Thanks and REgards,

Syam

Former Member
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I have a related question so posting to this same thread.

How much swap space is required on the server that runs HANA?  I realize that the HANA system will not use swap or page file to store tables, but it's possible that swap space may still be required for the OS or other operations on the server.  A common rule-of-thumb for sizing swap space on traditional servers is 1.5 x RAM, however I know that cannot be applicable with HANA.  Does anyone have a suggestion?

Thanks in advance,

Drew

Former Member
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Hi Drew

Reference from SAP Note Following table may give you some answers

http://sapbasiskishore.blogspot.com/2014/08/note-1597355-swap-space-recommandation.html

SAP recommends to use an amount of swap-space based on the table illustrated below. Customers may decide to use more or less swap-space based on their individual system configuration and their own experience during the day-to-day usage of a system. Physical Memory (RAM) Recommended Swap-Space


< 32 GByte 2 x RAM


32 - 63        GByte 64 GByte

64 - 127      GByte 96 GByte

128 - 255    GByte 128 GByte

256 - 511    GByte 160 GByte

512 - 1023  GByte 192 GByte

1024 - 2047 GByte 224 GByte

2048 - 4095 GByte 256 GByte

4096 - 8191 GByte 288 GByte


> 8192 GByte 320 GByte