Background: We are a film scanning and restoration service working primarily with archival film. We've been using a homegrown RAID with SATA drives for years as the RAID pool for our TigerStore SAN. I recently acquired eight Dell R515 servers from a friend's company that was decommissioning them. Each has a PERC H700 controller, and 12x 4TB SAS 6Gbps 7200RPM drives. Our goal is to migrate the older SATA RAID boxes over to these Dell servers. So I'm starting with one, running CentOS, which serves the volume up via iSCSI to our TigerStore server over our 40GbE network, (which in turn shares them with all the workstations that have the SAN drivers installed).
In our current setup we use RAID 6 volumes. This has been reliable and reasonably fast. RAID 5 was faster, but the extra level of redundancy with RAID 6 made me more comfortable because of course, drives fail. I would like to try to get better performance, so I'm looking at RAID 50, since that should be similar to RAID 6 in terms of safety, but with faster speeds. Right now we can do about 1GB/second Reads and Writes (faster on the reads usually) using the SATA RAIDs. I am hoping the SAS drives in the Dells will eke out a bit more speed, in part because the RAID pools are larger (12 drives vs 8). The sustained speed per disk is similar to the drives we have now.
The kinds of files we work with vary, but are all pretty big. They come in two forms:
1) Quicktime files: these are single movie files, and range in size from a few gigabytes to multiple terabytes (yes, per file). A typical file is 250-500GB in size. Most of the files we work with are Quicktime files.
2) Image sequences: these are folders containing sequentially numbered images, individual image sizes range from 12MB to 200MB, and there can be tens of thousands of them in a folder.
What I would like to get a handle on is the following:
- What are the optimal settings in the H700 controller for a middle ground that deals well with both formats? We need good read and write speeds, as these files are often played back in real time (sometimes faster than real time, such as when copying or rendering). I'm wondering specifically about read and write policies, as well as stripe size, but if there's other stuff to consider, I'm open.
- Is RAID-50 a good choice here? It seems to strike a good balance between speed, reliability, and capacity (we'll get about 30TB from each server).
I decided to just take a stab at it on Monday and set up a 12-drive pool to initialize on the controller as RAID-50 (background initialization because I saw no other option). More than 55 hours later, it's still only 75% done. The RAID is accessible, but I would imagine degraded because of the background init going on. That said, the performance is really, really bad. Very laggy (gaps of many seconds between files when copying a folder full of them) and with write speeds in the range of what I'd expect from a USB-2 external drive: bursts around 500MB/s for a moment then settling down to a 30Mbps or so average (according to Windows file copy dialog's stats). Is this because of the background init? Happy to wait until it's done but I would have expected more given the speed of the drives installed even with an init in progress.
Thanks,
-perry
In our current setup we use RAID 6 volumes. This has been reliable and reasonably fast. RAID 5 was faster, but the extra level of redundancy with RAID 6 made me more comfortable because of course, drives fail. I would like to try to get better performance, so I'm looking at RAID 50, since that should be similar to RAID 6 in terms of safety, but with faster speeds. Right now we can do about 1GB/second Reads and Writes (faster on the reads usually) using the SATA RAIDs. I am hoping the SAS drives in the Dells will eke out a bit more speed, in part because the RAID pools are larger (12 drives vs 8). The sustained speed per disk is similar to the drives we have now.
The kinds of files we work with vary, but are all pretty big. They come in two forms:
1) Quicktime files: these are single movie files, and range in size from a few gigabytes to multiple terabytes (yes, per file). A typical file is 250-500GB in size. Most of the files we work with are Quicktime files.
2) Image sequences: these are folders containing sequentially numbered images, individual image sizes range from 12MB to 200MB, and there can be tens of thousands of them in a folder.
What I would like to get a handle on is the following:
- What are the optimal settings in the H700 controller for a middle ground that deals well with both formats? We need good read and write speeds, as these files are often played back in real time (sometimes faster than real time, such as when copying or rendering). I'm wondering specifically about read and write policies, as well as stripe size, but if there's other stuff to consider, I'm open.
- Is RAID-50 a good choice here? It seems to strike a good balance between speed, reliability, and capacity (we'll get about 30TB from each server).
I decided to just take a stab at it on Monday and set up a 12-drive pool to initialize on the controller as RAID-50 (background initialization because I saw no other option). More than 55 hours later, it's still only 75% done. The RAID is accessible, but I would imagine degraded because of the background init going on. That said, the performance is really, really bad. Very laggy (gaps of many seconds between files when copying a folder full of them) and with write speeds in the range of what I'd expect from a USB-2 external drive: bursts around 500MB/s for a moment then settling down to a 30Mbps or so average (according to Windows file copy dialog's stats). Is this because of the background init? Happy to wait until it's done but I would have expected more given the speed of the drives installed even with an init in progress.
Thanks,
-perry