CentOS 7.9 LIO no memory buffer/cache used.

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francis
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Joined: 2018/12/16 19:08:00

CentOS 7.9 LIO no memory buffer/cache used.

Post by francis » 2022/09/01 13:30:20

Hello,

For a test environment with an old server I created a storage bay using CentOS 7.9 and LIO.

I have some RAID5 Logical Volume exported using ISCSI LIO to some VMWare servers.

The storage server have 32Go memory but no memory are used for the buffer/cache I have more than 30Go free.

On the storage server when I start io's (dd) on a logical volume, I see the memory buffer/cache used.

On a LIO client (VM on a VMWare server) when I do io's, on the storage server no memory buffer/cache are used.

This is not a problem with VMWare I have the same issue with a CentOS LIO client.

This is like LIO bypass the buffer/cache, on the storage server I "loaded" a Logical Volume in the buffer/cache (dd if=/dev/vg/lv of=/dev/null) and from the LIO client when I read de Logical Volume (dd if=/dev/sdx of=/dev/null) all the read io's come from the disk.

PS: I have and OpenMediaVault and TGT for the iSCSI with Logical Volume exported the buffer/cache (vmstat buff) is used.

Best regards.

Francis
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