SSD Drive options

@earlster - option B. Once the samples are on the RAID, they will rarely (if ever) change. It's really a database. I will occasionally add samples to the drive, but that's fairly infrequent (once a month at most - more likely, a few times a year).

Performance is paramount. It seems both RAID 0 and RAID 5 have excellent performance.

The drives will stream large amounts of audio data in real time. For example, I use the virtual piano instrument, Ivory 2. This one instrument alone has 77GB of data available for streaming (divided up into smaller files sizes). Often many of my sessions in Logic (music app) have 15-20 instruments, sometimes more.

RE: SSD vs 7200rpm - I've been told many times that 7200rpm cannot achieve speeds even close to SSD with regards to sample streaming. 7200rpm drives cannot reach the 500MB/sec transfer rate, even in a RAID.

If you need speed I would go with 10K drives or SSD. If you are going to do RAID they all need to be the same speed.

@earlster, you seem to assume files occupy contiguous chunks of space on hard drives. They don't. Head seeking happens while reading a single file. And sometimes, heads don't have to move when going from one file to another. Files get scattered.

unixiscool said:

If you need speed I would go with 10K drives or SSD. If you are going to do RAID they all need to be the same speed.

... and size.

I'm such an ignoramus. I've never heard of 10K drives before. Haha.

Can I RAID together drives of different sizes? (ETA: cross post with Tom)

Looking back at some of the earlier discussion I caught this:

"4 500GB SSD Drives in RAID 5 - 2TB total for virtual instrument music samples"

Unfortunately with RAID 5 you lose 1/3rd of the total space for parity, so you'd only have 1500 gb of usable space. You'd need 4 700GB drives to get 2TB.

Beyond that, you said 'performance is paramount' - So since RAID 0 performance should be better than RAID 5 that moves you to that configuration. It sounds like the reduction in downtime for a hardware failure isn't really a huge concern (not to say that it doesn't suck while it happens). Seems like you'd rather deal with an occasional failure instead of potentially encountering performance problems sooner.

If you RAID together different size drives, you have to format them all to only use the size of the smallest drive.

Tom_Reingold said:

@earlster, you seem to assume files occupy contiguous chunks of space on hard drives. They don't. Head seeking happens while reading a single file. And sometimes, heads don't have to move when going from one file to another. Files get scattered.

If you write them in one shot and don't delete/add then most file systems will write them contiguously. Once you start deleting and adding then you will start fragmenting the drive. Which can be fixed by using a defrag tool.
I'm really trying to look at composerjohn's special use case, for general use I fully agree with you, nothing beats SSD and RAID 0 is awful.

composerjohn said:

@earlster - option B. Once the samples are on the RAID, they will rarely (if ever) change. It's really a database. I will occasionally add samples to the drive, but that's fairly infrequent (once a month at most - more likely, a few times a year).

Performance is paramount. It seems both RAID 0 and RAID 5 have excellent performance.

The drives will stream large amounts of audio data in real time. For example, I use the virtual piano instrument, Ivory 2. This one instrument alone has 77GB of data available for streaming (divided up into smaller files sizes). Often many of my sessions in Logic (music app) have 15-20 instruments, sometimes more.

RE: SSD vs 7200rpm - I've been told many times that 7200rpm cannot achieve speeds even close to SSD with regards to sample streaming. 7200rpm drives cannot reach the 500MB/sec transfer rate, even in a RAID.

Since yours is a very special use case, I would follow the advice that you can find on forums dedicated to your specialty. I'm sure the people on some high performance audio/musicians forums have tried it all and have way more experience then I do.

One last comment. qrysdonnell has it right, RAID 0 has better performance then RAID 5 and in your case it even has a better failure rate. RAID 0 has two drives and if one drive fails it's dead. RAID 5 has 3 drives and while it will still work with one drive gone, the performance is heavily degraded and won't work for you anymore. So now you have an even higher risk of failure.

composerjohn said:

Can I RAID together drives of different sizes? (ETA: cross post with Tom)

Simple answer is 'no'.

Some background: The array would only be sized the equivalent of the smallest drive. Combining space on drives of different sizes would be a JBOD (Just a Bunch Of Disks) and you can't assume any improved performance beyond whatever drive happens to have the data on it.

There are some vendors with a technologies that can work around these limitations, but this thread had already gotten too complicated!

As far as what earlster alludes to above, when your RAID 5 is recovering, you likely won't have the required performance and while the RAID 5 rebuild may be faster than just resetting up your RAID 0 drives, there still will likely be downtime for your function - and the difference may not be that great. From a RAID perspective degraded performance isn't strictly downtime, from your perspective it likely would be.

Wow. Thank you all!

qrysdonnell said:

Looking back at some of the earlier discussion I caught this:

"4 500GB SSD Drives in RAID 5 - 2TB total for virtual instrument music samples"

Unfortunately with RAID 5 you lose 1/3rd of the total space for parity, so you'd only have 1500 gb of usable space. You'd need 4 700GB drives to get 2TB.

Holy! Great catch, thanks! I chatted with OWC and told them their advertising was a bit misleading for non-techies like me. To me, this implies 2TB with RAID 5 - http://eshop.macsales.com/item/OWC/TB4MSRSSD02T/. They should at least mention parity and losing space, even if it's a footnote. Not everyone knows this stuff! Appreciate the heads up!

earlster said:

Since yours is a very special use case, I would follow the advice that you can find on forums dedicated to your specialty. I'm sure the people on some high performance audio/musicians forums have tried it all and have way more experience then I do.

Despite the risks, it seems most music production use RAID 0 (best performance). Maybe I should come full circle and go back and consider RAID 0. I'll just make sure to have multiple backups in case of issues.

Is RAID 0 for two drives only? Or can you RAID 0 four drives?

qrysdonnell said:

As far as what earlster alludes to above, when your RAID 5 is recovering, you likely won't have the required performance and while the RAID 5 rebuild may be faster than just resetting up your RAID 0 drives, there still will likely be downtime for your function - and the difference may not be that great. From a RAID perspective degraded performance isn't strictly downtime, from your perspective it likely would be.

If the RAID 0 drives fail, does that mean the drives are garbage? Or, can they be reformatted and used again?

I can use the backup drives in case of failure (even with a 7200rpm drive connected via USB). The performance will probably suffer a little bit, but I can manage until I either replace or reformat the SSDs.

RAID 0 means exactly two drives. But there is RAID 1+0. Confusing, for sure. You take an array of two drives and make them into a RAID 1 array, i.e. the two mirror each other. Then you do the same with a second pair of drives. Then you pair the two pairs using RAID 0. Now you have four drives offering the space of two. The RAID 1 makes it resistant to disaster. The RAID 0 makes it fast, at least in theory; it would have to be done right.

@earlster, RAID 5 is not necessarily three drives. RAID 5 arrays have a minimum of three drives and a maximum so high I don't even know it. The unit composerjohn is considering has four drives.

composerjohn, earlster is right to recommend you follow your industry's best practices. But I fear RAID 0 so much that I'm just not comfortable recommending it. I still prefer RAID 5 or RAID 1+0. I strongly suspect that a four-drive SSD RAID 5 array will be sufficiently fast. I mean, SSDs are really, really fast already, then RAID 5 boosts that further.

Agreed, a RAID 5 will be plenty fast. But now I'm concerned about losing 500GB of space (out of the 2TB). I need that space. My current samples are around 1.2TB. I'll have little room for new samples.

I would think that RAID 1+0 is more expensive. For 2TB I'd have to purchase 4TB. Right? 1TB + mirror and 1TB + mirror.

composerjohn said:

qrysdonnell said:

As far as what earlster alludes to above, when your RAID 5 is recovering, you likely won't have the required performance and while the RAID 5 rebuild may be faster than just resetting up your RAID 0 drives, there still will likely be downtime for your function - and the difference may not be that great. From a RAID perspective degraded performance isn't strictly downtime, from your perspective it likely would be.

If the RAID 0 drives fail, does that mean the drives are garbage? Or, can they be reformatted and used again?

I can use the backup drives in case of failure (even with a 7200rpm drive connected via USB). The performance will probably suffer a little bit, but I can manage until I either replace or reformat the SSDs.

You should expect that failure means hardware failure, which means it's 100% broken and will never work again. In a RAID 0 setup you would have to get a replacement drive and then set the array back up and copy your data from your backup - so don't rely on only an off-site backup, as downloading 2TB will take a LOOOONG time. Although most backup services will offer the option of overnighting a disk. Now, only the one disk that failed (assuming both didn't fail at the same time, which is rare, but rare doesn't mean it never happens!)

With RAID 5 it can tolerate one drive failing. It will still work while the drive is failed. You replace the drive and rebuild the array to restore the fault tolerance. While the array is rebuilding you'll likely have a noticeable performance decrease (sometimes very noticeable). As long as a second drive doesn't fail while you're rebuilding (once again rare, but I have seen it happen) you'll be good and not experience any downtime. (Unless you count the time you're doing IT instead of composing as downtime, but we won't be too uptight here!)

Other common RAID configurations are RAID 6, which can tolerate two disks (when you have a 12 disk array you can figure out why you might want this) and RAID 1 which is mirroring. And RAID 10, which is RAID 1 and RAID 0 combined, which as we mentioned is the 'best practice' way to get the performance increase of RAID 0 without increasing your chance of a failure that will bring the array down. But this comes at the real-world expense of having to buy at least 4 disks.

Stupid question: is RAID 1+0 (Tom's suggestion above) the same as RAID 10? RAID 10 doubles the cost (which is already pricey) from $1480 to $2300. That's a big difference.

A RAID 0 at OWC would cost $949 (two 1TB SSDs) plus $247 for the enclosure (http://eshop.macsales.com/item/OWC/METB7DK0GB/). Total $1196. I can basically buy two RAID 0's for the price of RAID 10.

PS: yes, the enclosure linked above is Thunderbolt 1 (not 2). That shouldn't effect performance (according to OWC techs). Also, I'd have to get SSD adapters for $15 each.

RAID 1+0 and RAID 10 are the same thing. It's a 'nested' type of RAID, so the ways to refer to it aren't quite as set in stone as the older standard RAID configurations.

Also, you did ask if RAID 0 can have more than two drives. It can, but you're increasing your chance of a failure each time and also increasing your time to reconstruct the array after failure.

Not a stupid question, and yes, RAID 10 is another name for RAID 1+0. Yes, it's more expensive than RAID 5. RAID 5 is almost as cheap as JBOD, as it requires one more disk than you need, regardless of array size.

And if you go with RAID 1+0 be sure not to build as RAID 0+1. It's possible, and it's not good.

If you really need 2TB (and maybe more) and if you really need SSD, maybe you should have an array of more than four drives! This is where RAID 5 starts to shine, because with five or six drives, still only one is for parity (redundancy).

It seems the best performance and price would be:

A RAID 0, two 1TB SSDs and dual enclosure = $1196. If I ever have to replace the drives, it would cost $949 (assuming prices don't drop). That's still less than a RAID 10.

I'll have make sure to have 2 USB backups (alternating offline, per Tom's suggestion). If the SSDs fail, then I can use the USBs until I get a replacement.

The OWC drives have a 3 year warranty against failure. So, if something happened within that period, then I would receive replacements for free. I just confirmed this with OWC. There's no restrictions or conditions. If it fails within 3 years, even if used as RAID 0, they replace both.

Tom_Reingold said:

If you really need 2TB (and maybe more) and if you really need SSD, maybe you should have an array of more than four drives! This is where RAID 5 starts to shine, because with five or six drives, still only one is for parity (redundancy).

Do you mean something like 8 250GB SSD drives (totaling 2TB)? Would I only loose 250GB instead of 500GB?

8 250GB SSDs would cost around $1050. Then enclosure (8 bay?).

That would be the case, but I'd think you could easily spend more for a larger enclosure/controller to deal with it. A quick Google search looks like it could be $1400 or so. Also, while this method is more fault tolerant, 8 drives should be more fault prone than 2 - and take up more space, etc.

There may be something cheaper out there though. We generally buy expensive stuff at work (our normal workstations are ~$4000) so I'm sometimes out of touch with the prosumer level stuff that is out there!

I think the best choice for my needs is the RAID 0 with two SSD drives and backups. It's covered against failures for 3 years. It's easy, portable, and fast. I accept the risk. Fingers crossed!

Perhaps the biggest risk with RAID 0 isn't data loss but time loss. It could take a day or more to get back online. If that's OK, then it's OK.

That's true. But I can use the backup 7200rpm drive. I would just need to deal with possible performance issues. But I can work around that for a few days.

Tom_Reingold said:

Perhaps the biggest risk with RAID 0 isn't data loss but time loss. It could take a day or more to get back online. If that's OK, then it's OK.

It sounds like he'll be relying on a warranty replacement from the vendor, so he'll be out for at least however long it takes to overnight the equipment - that's assuming they send it overnight, of course, that's another thing worth knowing ahead of time. (@composerjohn - Once you're figured that out, you're pretty much a seasoned IT pro, time to update your resume!)

Haha, yes!

OWC takes 1-2 days for drive replacement. Just confirmed with tech support. Not too bad.

composerjohn said:

Haha, yes!

OWC takes 1-2 days for drive replacement. Just confirmed with tech support. Not too bad.

Yeah, not too bad. What's amazing is when you deal with Enterprise support with the likes of Dell and HP you can get replacement parts in 4 hours. It's pretty crazy.

I recently got a replacement drive from HP in two hours! Freaky!

But I had to call and ask for it. With netapp (an industrial server company), I have hot spares running in the system. When a drive fails, it emails netapp. Then I get a call saying, "Your drive is on the way." And I wonder, do I have a failed drive? Gee, I didn't know.