Notifications
Clear all

RAID 5 for SSDs

(@emattheis)
New Member Customer

I'm curious to know what SoftRAID's stance is on using SSDs in a RAID 5 configuration. There's seems to be mixed opinions about the suitability of SSDs in this RAID level. Concerns about increased wear seems to be the main theme, but I've also seen references to studies suggesting that uniform wear across the array also increases the probability of a multiple drive failure (I imagine this applies to more than just RAID 5 and SSDs, though). There's also the fact that some SSD controllers have RAID-like functionality built-in. Thoughts? Recommendations?

Quote
Topic starter Posted : 03/12/2015 11:15 am
(@softraid-support)
Member Admin

We test with SSDs all the time. We have users with RAID 5 RAID 1+0 and RAID 4, not to mention stripes and mirrors. There are no specific issues with SSD's that makes them vulnerable to issues because of RAID.

We have lots of users using RAID 1+0 with SSD's, especially for database applications such as FileMaker and servers. RAID 1+0 is especially suited when performance and data safety are the highest priorities.

RAID 4 with SSD is fantastic for mobile video applications, super fast, especially on playback and very portable.

we don't know of any specific disadvantages to RAID on SSD, except they are much more expensive.

I do not know what you are referencing by "RAID functionality" on SSD controllers. (Except perhaps SSD's installed/integrated onto PCI cards with striping built in to give incredible performance!)

We have done billions of I/O's on SSD disks in testing. We have special tools we created to test SSD's in particular. There are no issues we have seen caused by running RAID on SSD's.

Hope this helps!

ReplyQuote
Posted : 03/12/2015 12:19 pm
(@angelonyc)
Active Member Customer

I can't believe that multiple drives will fail at the same time.. Just like people, we may have the same genetics, environment, yet a sibling might die of a disease decades before the others..

Softraid endorses RAID5.. Check Other World Computing, and Softraid sites yourself.. That's what I went with.. Still get speed, but with some protection against loss.. Ultimately of course, you decide what works best for you...

I'm very happy with Other World Computers RAID systems, they come with a custom version of SoftRaid.. I think it is a well thought out design..

ReplyQuote
Posted : 03/12/2015 10:39 pm
(@softraid-support)
Member Admin

Multiple drives can fail at the same time. One of the many reasons is drives may have been exposed to static discharges when installed. They could have been thrown during shipping. They could be part of a batch of bad drives. They could be part of an entire series of bad drives (Example the Seagate 2-4TB Barracudas), there could be power surges or brownouts, etc.

So if one disk fails, you need to EXPECT a second one to fail and take immediate precautions.

What the first poster is probably referring to is if all 4 drives in a RAID 5 reach 30,000 + hours of use, yes, it becomes statistically more likely that they could fail at similar times.

ReplyQuote
Posted : 03/12/2015 11:06 pm
(@emattheis)
New Member Customer

What the first poster is probably referring to is if all 4 drives in a RAID 5 reach 30,000 + hours of use, yes, it becomes statistically more likely that they could fail at similar times.

Indeed. I stumbled across a post that suggested RAID 5 essentially guarantees that the disks in the array wear at the same rate due to parity distribution and suggested that novel approaches using a time basis for the parity assignment could help. I imagine this is probably only something one would care about when designing datacenter-scale arrays at which point you should already be considering things like sourcing from different vendors to avoid same batch defects and scheduled drive replacement.

ReplyQuote
Topic starter Posted : 04/12/2015 9:36 am
(@emattheis)
New Member Customer

I do not know what you are referencing by "RAID functionality" on SSD controllers. (Except perhaps SSD's installed/integrated onto PCI cards with striping built in to give incredible performance!)

I believe some SSD controllers treat banks of memory in much the same way as a RAID - striping for performance and/or duplicating data for protection. They may also have cleanup processes that optimize how data is stored across the cells akin to how a RAID controller can optimize data layouts across a set.

ReplyQuote
Topic starter Posted : 04/12/2015 9:43 am
(@softraid-support)
Member Admin

Your first point is probably true for large data centers. Most now use disks for 3 years and toss them.
(see backblaze's blog, who are very forthcoming on disks and how they are handled in their business)

To your second post, SoftRAID just sees what is presented to OS X. It is a "device" or "LUN", regardless of what is inside the box. So it does not matter what tricks the disk uses to increase its performance.

For example if you have a 2 disk hardware RAID box, such as one of the LaCie bigdisk enclosures, SoftRAID just sees a single device. It has no idea there are two disks inside. So everything works the same as if there were a single disk in the box.

The main difference is devices which use onboard RAID controllers do not pass full SMART data. In the case of SSD's this means the wear indicators are unavailable for example, so SoftRAID cannot tell you when it is getting close to wearing out. Same with HD's, SoftRAID cannot tell you when either disk is starting to fail inside such an enclosure.

ReplyQuote
Posted : 04/12/2015 10:22 am
(@angelonyc)
Active Member Customer

Also remember that everytime you boot up SOFTRAID5 scans and gives you an alert (can even send an email), that it is detecting errors on a drive.. SOFT RAID also mentions that if you act upon the warning, (or SOFTRAID icon on top right bar of mac screen is not blue).. You still have time to replace the troubling disk.

Also a good point to mention is to make sure you have a spare drive or two on hand, so you can immediately replace it..

All things being equal/not equal.. It's very hard to imagine all drives dying at the same time, or even within a reasonable time reference.. Of the 5 helium drives in my OWC raid, one makes more mechanical noise than the other 3.. Whether this means it will have a shorter lifespan, I don't know..

I have a 'tech head' friend, who works at a major audio/computer goods store.. The biggest issue for him in repairing parts, is noticing that capacitors that are sometimes nowhere near their stated value fail... This accounts for a lot of failures.. Even capacitors from the same batch/box from the same manufacturer..

ReplyQuote
Posted : 04/12/2015 9:22 pm
(@khoyt)
New Member Customer

I'm very happy with Other World Computers RAID systems, they come with a custom version of SoftRaid.. I think it is a well thought out design..

Can anyone give an idea what is custom about the version of SoftRaid provided by OWC?

Are there more or less features or just ???

Looking at the Thuderbay 4 Raid solution :-)

ReplyQuote
Posted : 09/12/2015 10:35 pm
(@softraid-support)
Member Admin

The only difference is that the bundled version of SoftRAID for Thunderbay only works with disks in an OWC Thunderbay enclosure. Otherwise, it is the exact same product.

ReplyQuote
Posted : 10/12/2015 4:17 am
(@bilbosoftraiduser)
Active Member Customer

Im unclear about which version of Thunderbay I have. I paid for the Thunderbay RAID edition which include a SoftRAID serial number, but as far as I can tell I'm using the full SoftRAID version. Are there 3 versions of SoftRAID - SoftRAID light (does that come with the non-raid thunderbays?), Thunderbay edition, and full version. Mine monitors my non-Thunderbay drives.

ReplyQuote
Posted : 24/12/2015 12:49 am
(@softraid-support)
Member Admin

There are indeed three versions of SoftRAID as you described. Some earlier purchasers of OWC Thunderbay received the license to the "full" version of SoftRAID. You are one of those.

OWC offers great telephone support on their products, but consider the difficulty trying to support RAID over multiple hardware configurations, enclosures, PCI cards, hubs, buses, types of drives, etc. It can get very complicated. So OWC only supports SoftRAID in the Thunderbay enclosures. We think that is a great idea, so users can be fully supported as needed. We created a version of SoftRAID that requires the disks to be in the Thunderbay to assist OWC to offer better support for Thunderbay purchasers. There is an upgrade path to the full SoftRAID for those who want to use SoftRAID on other disks.

ReplyQuote
Posted : 24/12/2015 1:03 am
Share:
close
open