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mdadm limit to 255 devices

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Brem Belguebli
Regular Advisor

mdadm limit to 255 devices

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 ?
4 REPLIES
Steven E. Protter
Exalted Contributor

Re: mdadm limit to 255 devices

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
Steven E Protter
Owner of ISN Corporation
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Gokul Chandola
Trusted Contributor
Solution

Re: mdadm limit to 255 devices

Hi,
Yes this is the limit.

Please try to manage within 255.

Regards,
Gokul Chandola
There is always some scope for improvment.
Brem Belguebli
Regular Advisor

Re: mdadm limit to 255 devices

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


Brem Belguebli
Regular Advisor

Re: mdadm limit to 255 devices

Thanks for your answers.

Thread closed.