[DRBD-user] Fw: DRBD SSD's and TRIM

Christoph Roethlisberger christoph at iway.ch
Tue Nov 15 12:21:29 CET 2011

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

Hello Håkan

>> secondary host/SSD. This is a bad thing to do with an SSD's since it
>> will conclude every block on the disk is occupied by "useful" data, and
>> it will have a large negative impact on the SSD's wear leveling
>> algorithm. Can somebody confim this conclusion ?
> Well, you can easily avoid the initial sync; as "unused" blocks will be
> returned as zeroes it won't cause "different" data on both sides.

I believe that this is no problem at all, as it writes only zeros (if the 
source disc is "really" empty). And any SSD should not taint the flash cells 
if it sees that a complete erase block (I believe this is between 2MB and 
8MB on todays SSDs?) only consists of zeros.

Why I come to this conclusion? On SSD discs without trim support and no trim 
utility from the vendor, it's a well known technique to use SecureErase and 
write zeros all over the disc, to restore factory default 
settings/performance for such discs. (and this works!)


We're using SSDs in production systems for ~3 years now and had only 
positive experiences so far. (we have way over hundred SSDs already deployed 
in servers) 

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