October 16, 201411 yr Wondering if anyone has tried to compare the SSHD drives (ST4000DX001) to a similar 7200 Drive. Is the speed really going to happen with something like unraid? Will unraid actually support the SSHD drives yet?
October 16, 201411 yr It depends on your use case. Most people use unraid for media storage. Sshd devices are not useful in this application. What is your use case? Sent using a portable device. Sorry for the tpyos.
October 16, 201411 yr Re: Seagate Hybrid Drive ST4000DX001 4TB MLC/8GB 64MB Cache SATA 6.0Gb/s NCQ 3.5" Desktop SSHD It's my belief that these could provide a benefit to unRAID'ers who have allot of frequently accessed small files. .nfo, jpg, etc, etc. It all depends on how much of those small files are accessed and at what frequency. In addition, since the drive caches the most often used LBA's, chances are, many of the directory structures would be cached into the 8GB SLC cache. So for applications that continually scan the drive's directory tree, this could provide a big boost in traversing the directory structure. case in point, We have 8GB in SLC cache. on my system, I scan the whole server for the stat() information (like find). I've stored it in sqlite and gdbm for size comparison. in SQLite, 1 million files of stat information takes up about 500MB. root@unRAID:~# ls -l --si /var/lib/sqlocate/sqlocate.sqlite3 -rw-r--r-- 1 root root 508M 2014-10-15 20:59 /var/lib/sqlocate/sqlocate.sqlite3 root@unRAID:~# ls -l /var/lib/sqlocate/sqlocate.sqlite3 -rw-r--r-- 1 root root 507951104 2014-10-15 20:59 /var/lib/sqlocate/sqlocate.sqlite3 root@unRAID:~# locate . | wc -l 1164677 Store stat data into gdbm cache. root@unRAID:~# /mnt/disk3/filedb/bin/ftwstatcache /mnt/disk3/filedb/statcache.gdbm /mnt/disk3 root@unRAID:~# enable -f /mnt/disk3/filedb/bin/gdbm.so gdbm root@unRAID:~# gdbm gdbm: usage: gdbm [-euikvr] [-KVW array] file [key | key value ...] root@unRAID:~# gdbm /mnt/disk3/filedb/statcache.gdbm | wc -l 202184 root@unRAID:~# ls -l /mnt/disk3/filedb/statcache.gdbm -rw-rw-r-- 1 root root 87826769 2014-10-16 11:10 /mnt/disk3/filedb/statcache.gdbm root@unRAID:~# ls -l --si /mnt/disk3/filedb/statcache.gdbm -rw-rw-r-- 1 root root 88M 2014-10-16 11:10 /mnt/disk3/filedb/statcache.gdbm In GDBM, 1 million files of stat information takes up about 200-300MB Taking the following information into account, this means that these files and/or all the frequently accessed LBA's that hold the directory information will be in the SLC SSD cache. Now if you are doing mostly writes to a cache and then moving the files off the cache, the SSHD probably wouldn't provide too much of a benefit. For a read mostly operation, it could provide a benefit for frequent scans. In my case, 300,000 mp3's on a drive that are write once in a while when adding files and read mostly. For an apps drive, that doesn't write often, it could provide a little benefit. For a cache drive that is used for spooling download data, I do not think it would provide more of a benefit over fast large 7200 RPM drive. Size of the drive matters in this case as larger 7200 RPM drives have very fast throughput on the outer tracks. It all depends on how much data that will be spooled and accessed. In my case I use a 2.5" 750 SSHD for my DJ laptop. After a few scans of the mp3 directory, it's lightning fast to scan it after reboots. In fact, this thread is making me consider some new drives for my mp3 drives as I'm starting to grow past the current drive size.
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