New on LowEndTalk? Please Register and read our Community Rules.
All new Registrations are manually reviewed and approved, so a short delay after registration may occur before your account becomes active.
All new Registrations are manually reviewed and approved, so a short delay after registration may occur before your account becomes active.
Comments
Hmmm guess not >.>
@Corey, I use them -- the flash module just replaces the BBU, the cache itself is still ram based but if the card loses power, the ram is written out to flash using power from super capacitors.
Capacitors are capacitors, what makes these super?
Goldcaps i suppose.
Edit:
Source
@jeff_lfcvps @mitgib
Nice, thank you very much for that information. I purchased a 6405 yesterday and I'm going to test it out.
So how about the ones that use SSD as cache? Sounds like you don't need a BBU or Flash Module for those? Could have a LOT more cache as well
Yeah, but will it have the same speed ?
M
Yes
@Maounique @FRCorey huh?
I don't see the ssd enabled raid card caching as a good use of funds on small arrays.
@miTgiB I'm not sure I understand. The 6405 only has 128MB of cache(few GB with the flash module)... while I'm sure it's REALLY fast compared to SSD cache.... you can still cache a lot more to that SSD and have a really good SSD to increase performance further.
Here with small you mean < 8 disks?
Yes, I see it is very common to use 4 disk raid10 arrays, but to use this ssd cache you use another port on the adapter, meaning you now need an 8 port adapter at near double the price, at least from what I have been seeing looking at the LSI line, that is how it seems to work. Just personal preference but I now avoid Adaptec. I've always liked 3ware/LSI over Adaptect, but I do own some Adaptec cards, but now I refuse to buy anymore.
I've seen the cachesomething (don't remember how the name it) in the latest lsi controllers but never tried it. I just fill in as much sas disks i can and never look back (until they die) :P
Even the lsi controllers powering the supermicro twin i bought lately have such tecnology..
Yes, but on the 9260 card, to enable cachecade or whateverthefucktheycall it is $200 more, then you are eating ports on a 8+ port card. the 9265 cards seem to have this feature already enabled I think, but the cards are even more than $200 more than the 9260. I bought the limit 5 this morning on some 64gb SSD and will play withflashcache kernel module instead, I think using existing onboard controller for the SSD and software to cache makes more economic sense at this point. Maybe in the future things will be different.
Yes, that look interesting, have you tried it before?
No, just have been following the project for about 6 months, but $65 for the SSD was priced to make me take the plunge and try it out. LFCVPS is using this from talking to guppy on IRC and he said he loves it.
@mitgib check these badboys out..
That's what you call a real super/ultra capacitor, super capacitors sort of act like short term batteries basically. Store lots of charge but don't last too long. I've got some massive 'uns at my uncles house, they're lethal..
Damn! now I need to build a custom box to try this... and time is never enough...
flashcache or capacitor destructon?
flashcache
ultrasuperiperdupercapacitors aren't my cup of tea....
Wow those ultracaps are cool.
like tantalum vs non-tantalum? at least we can call em super expensive..
@Corey, the size of the flash module is meaningless -- your cache is still based on how much ram your card has.
flashcache is a great little project -- we don't use it on any of our VPS stuff currently; however, it does wonders on our big slow SATA arrays that handle our maildir storage. I highly recommend it; however, you must make sure you understand the different caching types because there can be danger involved
Jeff, so you are using the flashcache module it seems :-)
Do you mind sharing your experience so far? :P
Edit: you wrote while I was composing the message...
Possible for you to elaborate on this?
It is all very detailed in this doc
https://github.com/facebook/flashcache/blob/master/doc/flashcache-doc.txt
After fumblefucking it up all day, we have liftoff!
About an hour worth of it running
[root@e3la17 ~]# dmsetup status cachessd 0 3803815936 flashcache stats: reads(1009870), writes(7908990) read hits(369666), read hit percent(36) replacement(24179), write replacement(0) invalidates(1) pending enqueues(0), pending inval(0) no room(0) disk reads(640214), disk writes(7909753) ssd reads(369666) ssd writes(640213) uncached reads(1), uncached writes(7909753), uncached IO requeue(0) uncached sequential reads(0), uncached sequential writes(0) pid_adds(0), pid_dels(0), pid_drops(0) pid_expiry(0)Well done man!
Are you generating synthetic traffic?