3 ms·

The memory can recover one, detect two, and will throw up loud warning bells to any competent admin as long as it is doing so. If you see a sudden spike of ECC

The memory can recover one, detect two, and will throw up loud warning bells to any competent admin as long as it is doing so. If you see a sudden spike of ECC errors from a server, the memory is probably bad, and you replace it. If you see a sudden spike of ECC errors from a large number of servers, something is seriously wrong, and you investigate - I'd be more likely to blame it on bad power myself, or a EM Field/radiation source. Even when trying to trigger rowhammer, the graph of bit flips is going to look like a logarithmic curve - Single-bit flips will be common, two-bits will be rare, and undetected flips will be real but ultimately not much to talk about compared to the discovered flips. You know they're there by the unrecoverable rate, and you replace the ram, discard any replicated data on that machine, and move on.

nkurz 11y ago
The memory can recover one, detect two, and will throw up loud warning bells to any competent admin as long as it is doing so. I don't have personal experience here, but one of the important claims in the paper is that this warning is not given on all servers: Unfortunately, server vendors routinely use a technique called ECC threshold or the 'leaky bucket' algorithm where they count ECC errors for a period of time and report them only if they reach certain levels of failure. From what we understand, this threshold is commonly above 100 per hour, but this remains a trade secret and varies based on the server vendor. So, to see ECC errors (MCE in Linux or WHEA in Windows), there generally needs to be 100 bit flips per hour or greater. This makes “seeing” Rowhammer on server error logs more difficult. In addition, we have observed some server vendors will NEVER report ECC events back to the OS,although they might get logged into IPMI. Typically, users expect to see correctable ECC errors logged directly to the OS or that halt the system when they cannot be corrected. During our investigation into this phenomenon, we even encountered one server that neither reported ECC events to the OS nor halted when bit flips were not correctable. The end result was data corruption at the application level. This is something, in our opinion, that should never happen on an ECC protected server system. http://www.thirdio.com/rowhammer.pdf http://www.thirdio.com/rowhammer.pdf
- baruch 11y ago
  On the servers that I use the server will log to ipmi sel only after a threshold but the Linux OS will get an MCE for each error so a monitoring tool can detect and alert even before the BIOS logs anything.
- BuildTheRobots 11y ago
  I really wish they'd have expanded on that somewhere and actually stated what manufacturers/models of server they tested and which ones don't report ECC errors.
  - brainfire 11y ago
    Really, without details like that it's just unverifiable FUD.

nkurz 11y ago

The memory can recover one, detect two, and will throw up loud warning bells to any competent admin as long as it is doing so. I don't have personal experience here, but one of the important claims in the paper is that this warning is not given on all servers: Unfortunately, server vendors routinely use a technique called ECC threshold or the 'leaky bucket' algorithm where they count ECC errors for a period of time and report them only if they reach certain levels of failure. From what we understand, this threshold is commonly above 100 per hour, but this remains a trade secret and varies based on the server vendor. So, to see ECC errors (MCE in Linux or WHEA in Windows), there generally needs to be 100 bit flips per hour or greater. This makes “seeing” Rowhammer on server error logs more difficult. In addition, we have observed some server vendors will NEVER report ECC events back to the OS,although they might get logged into IPMI. Typically, users expect to see correctable ECC errors logged directly to the OS or that halt the system when they cannot be corrected. During our investigation into this phenomenon, we even encountered one server that neither reported ECC events to the OS nor halted when bit flips were not correctable. The end result was data corruption at the application level. This is something, in our opinion, that should never happen on an ECC protected server system. http://www.thirdio.com/rowhammer.pdf http://www.thirdio.com/rowhammer.pdf

baruch 11y ago
On the servers that I use the server will log to ipmi sel only after a threshold but the Linux OS will get an MCE for each error so a monitoring tool can detect and alert even before the BIOS logs anything.
BuildTheRobots 11y ago
I really wish they'd have expanded on that somewhere and actually stated what manufacturers/models of server they tested and which ones don't report ECC errors.
- brainfire 11y ago
  Really, without details like that it's just unverifiable FUD.