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I've seen ECC mentioned a few times in this thread but how relevant is it really? At my old job we used both regular COTS hardware from Dell and HP and high-per

I've seen ECC mentioned a few times in this thread but how relevant is it really? At my old job we used both regular COTS hardware from Dell and HP and high-performance gear from SUN, often at four times the price. The latter had ECC memory and, if memory serves, shielded CPUs but I never noticed much difference in stability or performance when compared to regular hardware. If someone has some numbers on this, I'd love to see them.

lsc 16y ago
if your dell and HP kit was server grade, it almost certainly had ECC ram. before nehalam, it was almost impossible to get dual-cpu servers that would support non-ecc ram. Even today, now that unbuffered ram is supported (buffering and ECC are not the same thing, but it's unusual to see registered or buffered ram that is not also ECC) nearly all server hardware you get from the likes of dell or HP is going to default to using ECC ram. The big deal with ECC is that with non-ecc ram, you don't know when in-ram data was corrupted. If you have a bad bit of ram that is being used for our journaling/disk caching, it's pretty easy to corrupt your data. If you've got ECC, it corrects single bit errors, and logs that there was a problem, and it can be configured to crash on double bit errors, rather than just silently corrupting your data. If you use non-ecc ram, not only will bad ram silently corrupt your data, and sometimes crash your server, but there will be no indicator (other than random crashes) that the problem is in fact bad ram. You can get away with not having ecc in large server farms if you have lots of checksums on generated data... but in a VPS type situation where people get pissed if you loose a single server, it's sure to end in tears.
ableal 16y ago
James Hamilton (the Amazon VP linked to in another comment) also mentions lack of ECC in his appreciation of SeaMicro; he links to his own take last year, referring to studies with numbers: "You Really do Need ECC Memory in Servers" http://perspectives.mvdirona.com/2009/10/07/YouReallyDONeedECCMemory.aspx http://perspectives.mvdirona.com/2009/10/07/YouReallyDONeedE...

lsc 16y ago

if your dell and HP kit was server grade, it almost certainly had ECC ram. before nehalam, it was almost impossible to get dual-cpu servers that would support non-ecc ram. Even today, now that unbuffered ram is supported (buffering and ECC are not the same thing, but it's unusual to see registered or buffered ram that is not also ECC) nearly all server hardware you get from the likes of dell or HP is going to default to using ECC ram. The big deal with ECC is that with non-ecc ram, you don't know when in-ram data was corrupted. If you have a bad bit of ram that is being used for our journaling/disk caching, it's pretty easy to corrupt your data. If you've got ECC, it corrects single bit errors, and logs that there was a problem, and it can be configured to crash on double bit errors, rather than just silently corrupting your data. If you use non-ecc ram, not only will bad ram silently corrupt your data, and sometimes crash your server, but there will be no indicator (other than random crashes) that the problem is in fact bad ram. You can get away with not having ecc in large server farms if you have lots of checksums on generated data... but in a VPS type situation where people get pissed if you loose a single server, it's sure to end in tears.

ableal 16y ago

James Hamilton (the Amazon VP linked to in another comment) also mentions lack of ECC in his appreciation of SeaMicro; he links to his own take last year, referring to studies with numbers: "You Really do Need ECC Memory in Servers" http://perspectives.mvdirona.com/2009/10/07/YouReallyDONeedECCMemory.aspx http://perspectives.mvdirona.com/2009/10/07/YouReallyDONeedE...