Upgrade Areca cache memory, or system memory?

[wonderspark]

I have a 4,1 Mac Pro running an Areca 1880ix-12 w/BBU and standard 1GB of memory. It's for an 8-bay tower in RAID3 with 8x2TB WD RE4 HDDs. I get about 700MB/sec read, 750MB/sec write speeds sustained regardless of cache on or off on a 16GB test cycle when writing to 7 disks with #8 sitting as hot-spare.

Question: Will upgrading the 1880's memory from 1GB up to 4GB show any real-world gains, or would my money be better spent on a system RAM upgrade from 16GB to 32GB?

 

[nanofrog]

I have a 4,1 Mac Pro running an Areca 1880ix-12 w/BBU and standard 1GB of memory. It's for an 8-bay tower in RAID3 with 8x2TB WD RE4 HDDs. I get about 700MB/sec read, 750MB/sec write speeds sustained regardless of cache on or off on a 16GB test cycle when writing to 7 disks with #8 sitting as hot-spare.

Question: Will upgrading the 1880's memory from 1GB up to 4GB show any real-world gains, or would my money be better spent on a system RAM upgrade from 16GB to 32GB?

Cache would speed up writes in terms of what you notice generally speaking. But in the case of a 16GB file, it can't all fit in the cache anyway, so you end up seeing the set's actual performance capability.

A large enough DIMM would help as to what you notice/see in benchmarks (4GB is the largest it can handle according to Areca's site = useless for this big a file), but it doesn't change the speed of the actual set (just gets the data off of the system faster, but doesn't speed up the set itself). So to actually speed up the transfer of a 16GB test file, you'd really need to add more members to the set (additional parallelism).

Additional system memory won't fix this either, though that might help the applications used (need to check out your memory usage to see if this is viable or a waste of time and funds).

BTW, did you ever test out with a RAID 5 configuration?

 

[wonderspark]

I'm still using the data on the RAID3 volume, so I can't switch to RAID5 just yet.

I'll probably just chill out for a while. It all works swimmingly... I just get money that burns a hole in my pants now and then, which causes me to look for ways to improve my system. Looking at it again, I think system RAM is the only improvement I can make that will give real results right now.

 

[nanofrog]

I'm still using the data on the RAID3 volume, so I can't switch to RAID5 just yet.

This is one of the things a proper backup system is good for (backup, then reconfigure the drives into a different array).

BTW, the card is also capable of switching levels without data loss (called Online Migration).

The advantage to a backup besides not losing data in the event of a real failure, is that it's faster than Online Migration.

I'll probably just chill out for a while. It all works swimmingly... I just get money that burns a hole in my pants now and then, which causes me to look for ways to improve my system. Looking at it again, I think system RAM is the only improvement I can make that will give real results right now.

What about your backup situation?

I ask, as the comment about needing the data on the current array lends me to think you don't have a sufficient backup system in place (you must have one, or you will get burnt; just a matter of time as to when it will happen when you stick with RAID long enough, not if).

 

[wonderspark]

Well, I could switch to RAID5 because I do have it all backed up on another set of individual drives, but what I mean is that I'm using it on a daily basis right now, such that I can't afford to take days off to build a new RAID. It took 40 hours if I recall to build the RAID3, and if it ends up taking that long to build a new set, my clients will complain because I'm editing things for them right now.

If the set fails, sure, I'll have to build a new one, but it's different to have to tell clients that I suffered a failure when it really happens, as opposed to putting them off because I'm doing tests on the system. I'm sure they can appreciate the need for tests, but I think they'd like me to do that when time isn't so scarce.

This week, I'm trying to finish up another revision on a project before I leave for Costa Rica for a week on another project. Once I return from that, I will be expected to provide a new revision, and I think at that point I can spare a couple days. I admit that I've just returned (yesterday) from taking two weeks off the major project for a vacation in Hawai'i, but that's because I hadn't taken any time off in over two years, and I had a great opportunity to do so. As it was, I took one of my backup drives with me just in case, and the client only called me twice to do some quick edits, knowing I was on vacation.

I could tell them to leave me alone, but the reason I have this client is because their previous vendor didn't meet their needs to their satisfaction. They like that I provide for them, and I like that they have seemingly unlimited money to pay for my efforts.

I'm not trying to give you a hard time; rather I'm explaining why I haven't done further tests yet. I hope I'm not coming across as defensive or annoyed, because I'm not. I do have two sets of backups, though. I'm big on safety, especially when my livelihood depends on it!

 

[nanofrog]

Well, I could switch to RAID5 because I do have it all backed up on another set of individual drives, but what I mean is that I'm using it on a daily basis right now, such that I can't afford to take days off to build a new RAID. It took 40 hours if I recall to build the RAID3, and if it ends up taking that long to build a new set, my clients will complain because I'm editing things for them right now.

If the set fails, sure, I'll have to build a new one, but it's different to have to tell clients that I suffered a failure when it really happens, as opposed to putting them off because I'm doing tests on the system. I'm sure they can appreciate the need for tests, but I think they'd like me to do that when time isn't so scarce.

Understandable.

Generally speaking, it's always a good idea to allow yourself a couple of months for testing prior to taking a system online though (test out different levels relevant to the needs in terms of performance and fail over responses <test power outages, yank drives, ...>).

But as that wasn't the case, waiting until you have time makes sense (if you ever get the time, as the need to generate income is strong, and usually has to take precedence over other matters).

I'm not sure what all you were able to test before you began using the array for work (i.e. fail-over testing in particular so you know how it will behave in the event of a real failure), but the card itself will be fine (not just going to go "wonky" on you because you looked at it cross-eyed... ).

This week, I'm trying to finish up another revision on a project before I leave for Costa Rica for a week on another project. Once I return from that, I will be expected to provide a new revision, and I think at that point I can spare a couple days. I admit that I've just returned (yesterday) from taking two weeks off the major project for a vacation in Hawaii, but that's because I hadn't taken any time off in over two years, and I had a great opportunity to do so. As it was, I took one of my backup drives with me just in case, and the client only called me twice to do some quick edits, knowing I was on vacation.

2 years? That's it between vacations?!?!?

You may not know how lucky you are.

I could tell them to leave me alone, but the reason I have this client is because their previous vendor didn't meet their needs to their satisfaction. They like that I provide for them, and I like that they have seemingly unlimited money to pay for my efforts.

I don't blame you.

Repeat clients that pay their bills on time are worth their weight in platinum or diamonds (gold's too cheap ).

I'm not trying to give you a hard time; rather I'm explaining why I haven't done further tests yet. I hope I'm not coming across as defensive or annoyed, because I'm not. I do have two sets of backups, though. I'm big on safety, especially when my livelihood depends on it!

Not at all.

I was just curious, as there are plenty of valid explanations, usually related to time and money.