topic Re: mdadm limit to 255 devices in Operating System - Linux

mdadm limit to 255 devices

Brem Belguebli — Thu, 25 Sep 2008 18:38:50 GMT

Hi,
It looks mdadm is limited to 255 devices max, it refuses to assemble an array with minor number > 255

Setup: RHEL AS 4.6 and RHEL AP 5.2, SGLX 11.18, XDC 01.02

Any idea ?

Re: mdadm limit to 255 devices

Steven E. Protter — Thu, 25 Sep 2008 23:44:43 GMT

Shalom,

Everything has a limit.

Do you really want to assemble a raid array with more than 255 disks?

See about using a minor number less than 255.

sysctl -a

If this limit is controlled by a dynamic kernel parameter you may be able to raise it.

SEP

Re: mdadm limit to 255 devices

Gokul Chandola — Fri, 26 Sep 2008 02:20:47 GMT

Hi,
Yes this is the limit.

Please try to manage within 255.

Regards,
Gokul Chandola

Re: mdadm limit to 255 devices

Brem Belguebli — Fri, 26 Sep 2008 08:05:01 GMT

Hi,

Thanks for your replies.

Steven, it's not in terms of underlying devices as it looks you can have as much PV's as you want, or at least there is no 255 PV's limitations but in terms of /dev/md devices.

My need is that I'm building a SGLX cluster with XDC, for a few tens of databases which have distinct vg's for data, logs, etc..., vg's that will be paired by xdc (so md) and I'm afraid I'll be very fast reaching this limit.

Thanks anyway

Re: mdadm limit to 255 devices

Brem Belguebli — Fri, 03 Oct 2008 11:27:57 GMT

Thanks for your answers.

Thread closed.