<div dir="ltr"><div>Hi,</div><div><br></div><div>We are configuring lvm with SSD caching on some of our boxes in AWS. When the cache is initialised, we see this in logs:</div><blockquote style="margin:0px 0px 0px 40px;border:none;padding:0px"><div><p style="margin:0px;font-size:11px;line-height:normal;font-family:Menlo"><span style="color:rgb(175,173,36)">device-mapper</span><b>: cache: You have created a cache device with a lot of individual cache blocks (4915200)</b></p></div><div><p style="margin:0px;font-size:11px;line-height:normal;font-family:Menlo"><b> All these mappings can consume a lot of kernel memory, and take some time to read/write.</b></p></div><div><p style="margin:0px;font-size:11px;line-height:normal;font-family:Menlo"><b> Please consider increasing the cache block size to reduce the overall cache block count.</b></p></div></blockquote><div><br></div><div>Is this something to worry? If so, how can we improve it?</div><div><br></div><div>For reference, the output of lsblk is:</div><blockquote style="margin:0 0 0 40px;border:none;padding:0px"><div><p style="margin:0px;font-size:11px;line-height:normal;font-family:Menlo">NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT</p></div><div><p style="margin:0px;font-size:11px;line-height:normal;font-family:Menlo">xvda 202:0 0 25G 0 disk </p></div><div><p style="margin:0px;font-size:11px;line-height:normal;font-family:Menlo">└─xvda1 202:1 0 25G 0 part /</p></div><div><p style="margin:0px;font-size:11px;line-height:normal;font-family:Menlo">xvdb 202:16 0 152.6G 0 disk </p></div><div><p style="margin:0px;font-size:11px;line-height:normal;font-family:Menlo">└─md0 9:0 0 304.9G 0 raid0 </p></div><div><p style="margin:0px;font-size:11px;line-height:normal;font-family:Menlo"> ├─storage-cache_cdata 252:0 0 300G 0 lvm </p></div><div><p style="margin:0px;font-size:11px;line-height:normal;font-family:Menlo"> │ └─storage-data 252:3 0 1.5T 0 lvm /mnt/local</p></div><div><p style="margin:0px;font-size:11px;line-height:normal;font-family:Menlo"> └─storage-cache_cmeta 252:1 0 1G 0 lvm </p></div><div><p style="margin:0px;font-size:11px;line-height:normal;font-family:Menlo"> └─storage-data 252:3 0 1.5T 0 lvm /mnt/local</p></div><div><p style="margin:0px;font-size:11px;line-height:normal;font-family:Menlo">xvdc 202:32 0 152.6G 0 disk </p></div><div><p style="margin:0px;font-size:11px;line-height:normal;font-family:Menlo">└─md0 9:0 0 304.9G 0 raid0 </p></div><div><p style="margin:0px;font-size:11px;line-height:normal;font-family:Menlo"> ├─storage-cache_cdata 252:0 0 300G 0 lvm </p></div><div><p style="margin:0px;font-size:11px;line-height:normal;font-family:Menlo"> │ └─storage-data 252:3 0 1.5T 0 lvm /mnt/local</p></div><div><p style="margin:0px;font-size:11px;line-height:normal;font-family:Menlo"> └─storage-cache_cmeta 252:1 0 1G 0 lvm </p></div><div><p style="margin:0px;font-size:11px;line-height:normal;font-family:Menlo"> └─storage-data 252:3 0 1.5T 0 lvm /mnt/local</p></div><div><p style="margin:0px;font-size:11px;line-height:normal;font-family:Menlo">xvdg 202:96 0 1.5T 0 disk </p></div><div><p style="margin:0px;font-size:11px;line-height:normal;font-family:Menlo">└─storage-data_corig 252:2 0 1.5T 0 lvm </p></div><div><p style="margin:0px;font-size:11px;line-height:normal;font-family:Menlo"> └─storage-data 252:3 0 1.5T 0 lvm /mnt/local</p></div></blockquote><div><br></div>Thanks,<div>Ciprian<br clear="all"><div><div class="gmail_signature"><div dir="ltr"><div><div dir="ltr">--</div><div dir="ltr">Performance Monitoring * Log Analytics * Search Analytics<br>Solr & Elasticsearch Support * <a href="http://sematext.com/" rel="noreferrer" style="color:rgb(17,85,204)" target="_blank">http://sematext.com/</a><br></div></div></div></div></div>
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