I've been looking into installed a 128GB or 256GB SSD as a cache drive for my unRAID setup (18TB, all 2TB drives). But from what I can tell, because unRAID doesn't support TRIM, it's important to get an SSD with good automatic/idle-time garbage collection to ensure that the SSD doesn't slow down too badly over time.

 

I found this thread from a little while back that links to an xbit article that recommends plextor m3 and corsair performance pros drives for their garbage collection: http://lime-technology.com/forum/index.php?topic=20260.0

 

Since those drives are getting kind of old and not really broadly available anymore, does anyone have any recommendations for an SSD that would be good in the unRAID environment with good garbage collection? I write about 60-80GB a day to my unRAID system and don't want to bother with an SSD if it's going to degrade really bad in write speeds. Or should I just get a 7200rpm drive and skip the SSD for a cache drive for the time being?

7200 or even a raptor will be more than you need for a cache drive. Network is your bottleneck.

Unraid 5 has ext4 (trim support)  but then you need to script the mount and move is using for a cache drive.

 

Sent from my SGH-I727R using Tapatalk 2

 

 

OCZ Vertez 4 seems to do a good job with GC, if the drive reach idle or if it reaches 85% of used blocks:

 

http://www.anandtech.com/show/5719/ocz-vertex-4-review-256gb-512gb/8

I always suggest a fast drive, but as large as your parity. That way if you loose a drive in the system, in a pinch you can swap out the cache functionality, rebuild the failed drive and order a new cache or parity drive.

I recently tested one of the newer 3TB 7200 RPM Seagate drives with 1TB platters. I was blown away by the speeds I was getting during preclear.

 

 

My tests were showing over 190MB/s on the outer tracks.

Since you are dumping data and moving it without the need for high speed random I/O, it may be worthwhile to consider the expenditure.

If you were more concerned with spinning up a drive to drop off files, then an SSD with cache onboard could serve to assist. I recently purchased the Samsung 840 pro. Not sure about the GC, but from what I remember the drives that had a larger cache usually did well with GC.

If you want to hold out a bit Tom just announced that he will be adding cache pooling which will use btrfs as the file system. This is an SSD aware file system and will make looking for drives with very good hardware garbage collection unnecessary. Another advantage of cache pooling will be you can use cheaper, smaller drives to create a larger pool that will then have fault tolerance so if a drive fails you will not lose any data on the cache.

I'm kind of with weebo on this one. and I use SSD's and raid5 arrays for my cache drives.

 

If you pick up a 1TB - 2TB or 3TB seagate with the 1TB platters and use that for a cache, it will be faster then your network.

also, you have a warm spare if a drive fails.

plus, if you run out of array space and no drives are on sale that week or you're between checks,  you can toss the cache drive into the array and order a new cache drive.

 

the one huge advantage to an ssd is you can write to it while its running the mover and it will still be as fast. but it wont be a problem for most.

 

 

If you want to hold out a bit Tom just announced that he will be adding cache pooling which will use btrfs as the file system. This is an SSD aware file system and will make looking for drives with very good hardware garbage collection unnecessary. Another advantage of cache pooling will be you can use cheaper, smaller drives to create a larger pool that will then have fault tolerance so if a drive fails you will not lose any data on the cache.

 

 

btrfs is supposed to support trim also.

 

 

but I'll still say, if you are just looking for network speed, consider the 3TB 7200 RPM Seagate.

I did get over 190MB/s during a preclear for a good portion of the drive's capacity.

If you are looking to save power and not have a drive spin, then go with SSD.

If you are looking to save power and not have a drive spin, then go with SSD.

 

true, but if you move a lot of data, you will run the mover more times a day. and then you have the whole array chugging and eating more power in the long run

 

but its always ready to take data without a spinup is nice.