[DRBD-user] device size limit <= 2TB for DRBD disk on DRBD <= 0.7.3

Helmut Wollmersdorfer helmut.wollmersdorfer at gmx.at
Wed Sep 1 16:07:01 CEST 2004

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

Philipp Reisner wrote:

> There are several Limits involved:

> 1. The 32bit overrun in DRBD's size determination code.
> 2. The limit in the kernel's vm - space. Limiting the memory for the bitmaps.
> 3. Current meta-data layout allows 3.8TB per device.

> (1) will be fixed rather soon. 

ACK. Allowing overruns (=> wrong data, unpredictable side effects, 
crash) is IMHO a bug. According to usual classification systems, a bug 
causing data damage or crash has severity critical.

> (2) applies only to i386, this is not an issue on an 64 bit architecture
>     If LINBIT's customers demand a fix for this problem, we will fix it
>     for i386 -> I.e. if you want to have that limit removed, ask LINBIT!

That's a limit of hardware/architecture. Personally I would move to 64 
bit hardware, if I would have the need for such large amounts of data.

> (3) Will be on drbd-8's roadmap.

ACK. I assume low priority now, but in 2 years there can be a stronger need.

Helmut Wollmersdorfer

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