[DRBD-user] drbd size limit

David Huang david_huang at proware.com.tw
Tue Oct 4 10:35:29 CEST 2005

Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.

I am quite interested in this question as well.

I wonder how large can a DRBD device be under 32bits environment? because the barrier in my testing environment is 2TB (with vmalloc=192M kernel option, * a strange thing is that Fedora can set up vmalloc up to gigabyte, but I can not do it with offical kernel), anything over 2TB crashes my machines. Is there any possibility to make a 4TB DRBD device in 32 environment?? if source code modification or kernel tunning is a necessary, where should I begin with? 


David Huang

-----Original Message-----
From: drbd-user-bounces at lists.linbit.com [mailto:drbd-user-bounces at lists.linbit.com]On Behalf Of Lars Ellenberg
Sent: Friday, September 16, 2005 5:36 PM
To: drbd-user at lists.linbit.com
Subject: Re: [DRBD-user] drbd size limit

/ 2005-09-16 05:13:02 -0400
\ David Bernick:
> but do you think, gut feeling again, as you know this software better
> than i do, that if a host is 64-bit that it will work with devices
> that are larger than 4TB (9TB in this case)? Is the main limitation
> the fact that the metadata is 128MB?
> Actually, that should have been my question:
> ==> what is the limitation on device size? the metadata? <==

first limitation 4TB (well, 3.998TB): size of meta data, right.
after you break through this, you will hit other limitations,
e.g. those where some ints wrap. since we decided to have the 4TB limit,
and this masks the other, later limitations, I just cannot say from the
top of my head wether you will hit the next limitation at 4.7, 6, 8, 17,
or 16384 TB :-]
though, probably I should know.

: Lars Ellenberg                                  Tel +43-1-8178292-0  :
: LINBIT Information Technologies GmbH            Fax +43-1-8178292-82 :
: Schoenbrunner Str. 244, A-1120 Vienna/Europe   http://www.linbit.com :
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