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Hi
We're using SUSE Ent Storage - Ceph
And have Dell 730xd and expansion trays with 8 tB disks
We initially had the controller cache turned off as per ceph documentation (so configured as jboss in Dell Bios)
We reconfigured as raid0 and use the cache now for both internal and expansion drives
here is a Dell/Red hat document that discusses it (on page 20)
HTH Joe
>>> Tim Bishop <tim-lists@xxxxxxxxxxx> 3/14/2018 12:42 PM >>> I'm using Ceph on Ubuntu 16.04 on Dell R730xd servers. A recent [1] update to the PERC firmware disabled the disk write cache by default which made a noticable difference to the latency on my disks (spinning disks, not SSD) - by as much as a factor of 10. For reference their change list says: "Changes default value of drive cache for 6 Gbps SATA drive to disabled. This is to align with the industry for SATA drives. This may result in a performance degradation especially in non-Raid mode. You must perform an AC reboot to see existing configurations change." It's fairly straightforward to re-enable the cache either in the PERC BIOS, or by using hdparm, and doing so returns the latency back to what it was before. Checking the Ceph documentation I can see that older versions [2] recommended disabling the write cache for older kernels. But given I'm using a newer kernel, and there's no mention of this in the Luminous docs, is it safe to assume it's ok to enable the disk write cache now? If it makes a difference, I'm using a mixture of filestore and bluestore OSDs - migration is still ongoing. Thanks, Tim. [1] - https://www.dell.com/support/home/uk/en/ukdhs1/Drivers/DriversDetails?driverId=8WK8N [2] - http://docs.ceph.com/docs/jewel/rados/configuration/filesystem-recommendations/ -- Tim Bishop http://www.bishnet.net/tim/ PGP Key: 0x6C226B37FDF38D55 _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com |
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