简体繁体 English

Ceph存储可用空间计算

[英]Ceph storage usable space calculation

原文 2018-09-10 05:08:27 8 1 openstack/ ceph

Can some help me with below question. 可以帮助我解决以下问题。

How I can calculate total usable ceph storage space. 我如何计算可用的ceph总存储空间。 Lets say I have 3 nodes and each nodes has 6 OSD of 1TB disk . 可以说我有3个节点，每个节点有6个1TB磁盘OSD。 That is total of 18TB storage ( 3* 6TB ) .All these 18TB space is usable or some space will go for redundancy ? 那总共是18TB的存储（3 * 6TB）。所有这18TB的空间都是可用的，还是会有一些空间用于冗余？

1 个解决方案

Ceph has two important values: full and near-full ratios. Ceph有两个重要的值：完全比率和接近完全比率。 Default for full is 95% and nearfull is 85%. 满的默认值为95％，接近满的默认值为85％。 ( http://docs.ceph.com/docs/jewel/rados/configuration/mon-config-ref/ ) （ http://docs.ceph.com/docs/jewel/rados/configuration/mon-config-ref/ ）

If any OSD hits the full ratio it will stop accepting new write requrests (Read: you cluster stucks). 如果有任何OSD达到最大比例，它将停止接受新的写入要求（读取：将卡住群集）。 You can raise this value, but be careful, because if OSD stops because there is no space left (at FS level), you may experience data loss. 您可以提高此值，但要小心，因为如果OSD由于没有剩余空间而停止（在FS级别），则可能会遇到数据丢失的情况。

That means, that you couldn't get more than full ratio out of your cluster, and for normal operations it's wise to not reach nearfull value. 这意味着，您无法从集群中获得超过满负荷的比率，对于正常操作，明智的做法是不要达到接近满负荷的价值。

For you case, with redundancy 3, you have 6*3 Tb of raw space, this translates to 6 TB of protected space, after multiplying by 0.85 you have 5.1Tb of normally usable space. 对于您来说，使用冗余3，您有6 * 3 Tb的原始空间，这相当于6 TB的受保护空间，乘以0.85后，您就有5.1Tb的正常可用空间。

Two more unsolicited advises: Use at least 4 nodes (3 is a bare minimum to work, if one node is down, you have a trouble), and use lower values for near-full. 另外两个不请自来的建议：至少使用4个节点（如果有3个节点无法正常工作，则至少要工作3个），并使用较低的值表示接近满。 I'd advice to have it around 0.7. 我建议将其保持在0.7左右。 In this case you will have (4 nodes, 6 * 1Tb OSD, /3, *.7) 5.6 Tb of usable space. 在这种情况下，您将拥有（4个节点，6 * 1Tb OSD，/ 3，*。7）5.6 Tb的可用空间。